Dr. Naveen Kumar Archives - Poultry TRENDS

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Understanding Recent Feed Refusal And Poor Feed Intake

“Higher the consumption, better is the performance” is a popular saying amongst the poultry fraternity. This popular saying may not be a universal scientific truth but it surely highlights the importance of feed intake (consumption) in the performance of the flock as the amount of feed consumed by poultry is closely associated with the growth performance. Ever growing genetic potential of broilers is further demanding the increase in feed intake by the birds as modern commercial broilers will not grow to their full genetic potential unless they consume their full nutritional requirement each and every day. Simultaneously, it is also now accepted that with higher sustained genetic potential, we now have bird strains that are perhaps more sensitive to any given diet change. Scientific community have equivocally reported that beside adequate diet formulation, maintaining maximum feed intake is the single-most important factor that will determine the rate of growth and efficiency of nutrient utilization in birds.

**Dr. Naveen Kumar**
Business Director
Delst Asia (South Asia)

A slight or ‘transient feed refusal’ is quite common in broilers when the pelleted diet is first introduced in the feeder but recently a rampant increase in the feed refusal incidences have been reported both from poultry farmers as well as the feed milling industry that too from across the different climatic zones and in different time of the year.

To understand this sudden increase in the feed refusal incidences at the farms, it is highly imperative that first we understand the fundamental physiological theories which explains the feed intake control in birds.

Unlike mammals, there is no one theory which explains the control of appetite or feed intake in birds but the most accepted theory explains that a number of signals arrive at the cerebral cortex or hypothalamus and stimulate those nerves that pass through the hypothalamus, from where other nerve networks transmit information to the organs, such as the gizzard, liver, intestine and pancreas. These signals come directly from the food itself (color, shape and smell), whereas others originate from the intestinal tract following the ingestion of food. In contrast to mammals, visual and textural properties of food have a much greater influence on feed intake of birds than taste or smell. The bird will not readily consume feed if it does not recognize it as food by visual means. Birds are also quite sensitive to shape.

Feed Refusal – Dietary or Sensory?

There are several factors which can cause feed intake problems in the broilers and may be broadly categorised as:

Dietary Factors &
Sensory Factors

Dietary Factors: Dietary factors that influence feed intake is mainly related to dietary nutrient composition (either deficiency or in excess to the bird’s requirement). Dietary energy has the most predictable effect on feed intake of broilers birds. Feed intake will decrease as dietary energy content increases and will increase as dietary energy content decreases, until it is limited by either gut fill or other physiological limitations. Layer birds manifest better adjustment in their energy consumption as a consequence of dietary energy concentration than the broiler. Dietary protein and amino acid content have more of an indirect effect on feed intake than any direct effect. Similarly, dietary vitamins and minerals, anti-nutritional factors produced by fungal or microbial metabolism in the feed including managemental issues regarding access of feed and water apart from environmental or disease factors also have its effect on feed intake.

Mostly, if the feed refusal is because of dietary factors, this would be common among all flocks rather than one or selected individual flocks.

Sensory Factors: Sensory factors that influence feed intake can be categorized in three basic stages of food ingestion:

1. Food Recognition;
2. Food Prehension & Ingestion; and
3. Gastrointestinal Activity.

Every time a nutritionist formulates a feed formula with new ingredients, it doesn’t only change the nutrient composition but also the feed pelleting ability during feed processing in the feed mill as well as its final palatability by the birds because of its major change in feed texture. Changes in the physical characteristics of the feed are the main reason behind sensory influences or an alteration in the feed intake. Main physical characteristics of pellets feed texture (dryness & moisture), feed hardness/density, feed colour, feed taste etc.

The physical nature of the feed, namely, the combination of feed texture and hardness, are the overwhelming factors impacting feed intake at the time of diet change, as clearly seen in the transition from crumbs to pellets in young broilers. Changes in ingredient composition and nutrient profile are intimately linked, and together can represent an important additional novel change during this transition. Feed colour and taste are of lesser importance but this maybe because we don’t yet fully understand their significance to the bird.

Recent trends of feed refusal observed in several broiler farms across India have been quite baffling. The pelleted feed from the same batch, supplied to several broiler farms have not only reported farm to farm variation in the feed intake but also some incidences of complete feed refusal. Though it is often difficult to identify the root cause problem of feed refusal unless a complete review of feed and management practices is made but surprisingly sooner the farm switched to a different batch or say new brand of pelleted feed from different manufacturer, the feed intake was immediately resumed. This clearly highlighted the sensory challenges being presented in that particular pelleted diet.

After careful comparative observations between several pellet samples, it was generally noticed that feed texture and pellet hardness were the two most distinguished factors responsible for the rise of feed refusal or scratching incidences at the farms.

Feed texture

Let’s talk and discuss more about the feed texture aspect first. Feed texture is the most important factor which influences the feed consumption in the birds. Mechanoreceptors and chemo-receptors clustered in the birds mouth (taste buds), helps the birds rapidly gauze the feed’s quality by its textural properties. Chickens have an average of about 360 taste buds, out of which approx. 50% located in the palate, around 40% in the floor of mouth, and rest only 4% in the tongue. This taste bud distribution in the buccal cavity of the poultry is directly associated with the contact time of the feed on the different areas of the mouth to enable better gustatory discrimination. Even though poultry have far less number of taste buds than mammals, they do have a good sense of taste and changes in taste. Research papers also concluded that birds are more responsive to weakly flavored foods than strongly flavored foods indicating that a bird’s sense of taste can be overwhelmed.

Also, because of the very high degree of keratinization of the beak, birds have very little ability for oral manipulation of the any kind of feed offered. Feed particles must first be picked up and positioned by the beak and then a forward thrust of the head along with particle release moves the feed to the back of the mouth where it is coated with viscous saliva before swallowing. If the feed is too finely ground and not properly pelleted, it interacts with the saliva and forms a sticky mass that solidifies and interferes with prehension, especially when the diet contains high percentage of broken rice, millets, wheat or other small grains. Researches have confirmed that though mouth cavity of poultry is quite dry, there is a certain role of saliva to first moist and lubricate even the drier feed to push it well down the esophagus.

Though chickens are considered seed-eaters, the efficiency of feed intake is greatly dependent upon the particle size and shape that complements the physical attributes of the bird’s mouth. And this makes uninformed feed milling and feed processing a complete ‘no’ to the feed industry. Birds have clear cut difficulty in consuming pellets that is too large or too small relative to the dimensions of its beak. As poultry do not have teeth, so large particles or pellets cannot be “bitten” and divided into smaller ones. But simultaneously research also suggests that when given a choice, young broilers prefer large particles and generally avoid the smallest particles. Although poultry can apprehend fine feed, they cannot do it efficiently without significant feed wastage. Moreover, they must work more to consume a fine feed than pelleted feed, essentially reducing the productive energy of the feed. If the diet is offered as a meal, consumption will diminish in the young bird when particle sizes are small. If the mean diameter is below 0.8 mm this response becomes clearly noticeable. The depressive effect is proportional to the reduction in mean diameter of the particle. On average each reduction of 100 microns (0.1 mm) is associated with a decrease in intake of 4%. That is the reason why finely ground feeds are poorly consumed by poultry.

Generally the pellets are processed poorly under extreme low moisture and high temperature (with or without high die compression) conditions in tropics, which causes both Maillard Reaction Products (MRPs) as well as Caramelization (a hardened candy effect on the pellet surface) giving the impression of a well formed pellet but a very rough, brittle and a hard pellet surface which poorly affects the feed texture. At the similar die compression and conditioning temperature, the Maillard effect is most profound in all those pellets where moisture lack in penetrating the feed chemistry (particular to starch) which causes the glucosidic link to break away in excessive frictional heat inside the die passage and to react with the lysine. Though not reported, but this could be an interesting future research on Maillard, which involves aldol condensations (an aldehyde-amine condensation reaction) leading to the formation of polymeric compounds called “Melanoidins” (this is what we see in the darkened bread crust) on the surface of pellet and which may be negatively affecting its feed texture and taste.

The presence and proper penetration of water in feed chemistry not only affects the pellet texture but also its structure and uniformity. Even the small amounts of bound water that occurs in feed may have a marked effect on the pellet texture. Feed industry high dependence on PDI (Pellet Durability Index) as only benchmark parameter for pellet quality is certainly now playing a detrimental role to further improve the processed pellet feed quality.

Final moisture available in the pellets have a great significance on determining its texture which make the pellets appear either soft, rough or smooth. Total moisture of the pellets can be defined as bound moisture which is the initial moisture in the ingredients plus added moisture from steam condensation and water added at mixing, if any. In a field survey, we observed that feed pellets with higher than 11.5% total initial moisture had the lowest hardness or feed refusal issues at farms but as the total moisture kept going low below < 10% and up to 8-9%, there was significant increase in pellet hardness along with feed intake issues. Possible explanation of this phenomenon is that relationship between gelatinization and pellet hardness. The feed pellets with higher degree of gelatinization might be softer than the ones with lower degree of gelatinization which is related to the superior distribution of gelatinized starch across the pellets. In general, pellets having adequate moisture content exhibited a texture that is moist, juicy, tender and chewy. But in the pellets where moisture content got lowered, undesirable textural attributes such as dryness, hardness or tightness occurred to the pellet.

Hardness

In a random field study conducted in Northern region of India (Haryana & Punjab), broiler feed pellets (of 3 mm diameter, at average PDI >80) collected from different feed mill factories have shown that broiler farms fed with the pellet hardness range of 2.4 to 3.8 Kg/N and a final moisture range of 10.5 to 11.5% have got significantly higher feed intake than the pellets with hardness range of 4.0 to 5.2 Kg/N and having a moisture range of 8.5 to 10%. Once the hardness of pellets exceeded more than 5 Kg/N and moisture range remained under 10%, complete refusal of pellets was reported from the maximum number of the farms. Hardness of the pellets is defined as the amount of force required to crush the pellet and it can be calculated based on hardness value by dividing the hardness or maximum force to break the pellet (N) by the surface area of the probe (m2). The length of each pellet sample was controlled at the average of 8.5 ± 0.3 mm and diameter at the average of 3.0 ± 0.2mm.

Pellet hardness was analyzed by diametrical compression with Hardness Analyzer (supplied by M/s Insize Co. Ltd.) while the moisture was analyzed with (Portable Moisture Analyser and MX-50 Moisture Analyser).

Pellet Durability Index (PDI) was determined by putting 500 gm of feed pellets into a tumbling box and spinning at 50 rpm for 10 minutes.

Other Factors

Apart from pellet texture (dryness) and hardness, colour, taste and nutrient/ingredient composition may also contribute to feed refusal but may not be as negatively as these former two sensory factors. A transient change in feed intake or refusal may happen because of ingredient /color or taste in response to feed regime change, but it is clear that the main factor impacting ‘feed refusal’, is feed texture and hardness. For broilers, the most challenging and noticeable period of ‘feed refusal’ is reported at the time when the change from starter crumbs to grower pellets happened.

Graded Response to Feed Refusal

The fear of feed refusal that broilers “wont feed pellets” at an early stage of growth cycle has pushed several poultry growers in the country as well as feed manufacturers in several markets to produce and offer crumbs even much later in the production cycle. There are lots of feed millers who are producing and selling even ‘finisher crumbs’ ignorant to the fact that feeding crumbs will have a bigger impact on reduced growth than accepting any transient feed refusal at an early stage. Not a single research paper has been found which supports feeding of crumbs to finisher birds. But, nutritionist and manufacturers have not only to formulate and process a well nutrient balanced pellets but also a pellet which is easily acceptable and easy to ingest.

The rising incidences of feed refusal and lower feed intake is delaying the introduction of pellets change because of the perception that young birds “will not eat pellets”, this is ensuring reduced feed efficiency. We cannot expect the same feed efficiency of birds fed pellets (vs small crumbs) introduced at 15th day vs as late as 24th day. Research papers also do not support this argument that changing to pellets diet sets the bird back by 2-3 days. Meticulous observations also reveals that for individual birds transient ‘feed refusal’ is observed mainly in the first 20 minutes but that within 24 hours of the diet change, there is compensatory feeding that normalizes, or even exceeds, expected feed intake for that day.

Careful observations have also revealed that the broilers initial reluctance to eat pellets is associated with certain behavioural changes. Birds actually approach the feeder more often at this initial change of feed regime time, but this is often associated with a ‘closed beak’ which supports the observation of birds ‘playing’ with the feed or even scattering feed onto the litter. In the first 20 minutes there are also more instances of birds picking up the pellets but not swallowing them, so again they may be dropped onto the litter. In another report, dropping pellets onto the litter increased 10-fold in the first 20 minutes after initially offering pellets, although actual wastage was just a few gm/bird. However, pellet hardness and colour have been shown to have little impact on this transient ‘feed refusal’ behaviour.

To handle this issue of transient feed refusal at poultry farms which is an inevitable and inherent behaviour, one can add 5% pellets to a crumbed feed 5-7 days ahead of the changeover is one approach that can make sure that birds have access to some pellets prior to the changeover as one approach. Another obvious approach to reduce the adjustment time to any change in feed regime at farms is to feed 50:50 (crumbs: pellets) as the first delivery.

However, when the refusal of feed is prolonged and feed intake doesn’t get normalized within the couple of days at farms, immediate attention should be paid to improve sensory factors like feed texture and hardness along with the total moisture in the pellets.

Conclusion

As with many situations in life, poultry do not like change in any aspect of environment including the diet change. The poultry likes consistency in its environment, including in its diet, and to some extent ingredients used to formulate its diet. However, there is surprisingly little information available on how broilers respond to these abrupt ingredient/diet changes that are necessary as part of modern lifecycle feeding regimes. Once the poultry have become used to one form of presentation of feed, a certain amount of adaptation is necessary if another is provided. And, to help this adaptation, feed millers & processors now have increasingly bigger role to maintain major sensory factors of diets like feed texture (smoothness, dryness, softness) and hardness. Poultry that are fed pellets will need some time to get accustomed before being able to eat the same quantity of feed if the ingredient or diet are to be changed to a meal. Maintaining major sensory factors like feed texture including pellet dryness/hardness will surely reduce this adaptation or shorten the adjustment time for poultry in the farms. Change in the taste and smell of diets are pretty less sensitive to poultry, if compared to mammals as observed in the farms and may not be that important as sensory factors.

About the author:

Dr Naveen Kumar, B.V.Sc & A.H (Gold Medalist), M.V.Sc (IVRI, Bareilly) is a food & oil seed grains storage specialist and a finished feed quality expert for Asian and other tropical countries. He also Business Director of Delst Asia and is located in Faridabad, India. He can be reached at naveensharma21@gmail.com, Mobile +91 93502 89123.

Title Image Source: FreePik

Article by same Author: Pellets: “High Fines” Might Exaggerate Diseases At Poultry Farms

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19 min read

Pellets: “High Fines” Might Exaggerate Diseases at Poultry Farms

Pelleting is system of a modification of the mash system by mechanically pressing the mash into hard dry pellets or “artificial grains”. It is generally accepted that, compared to mash, the feeding of pellets improves feed conversion, broiler performance with an increased feed intake.

Reasons for the enhanced performance may be due to increased digestibility, decreased ingredient segregation, Decreased feed wastage, reduction of energy during prehension and improved palatability and so the modern broiler industry has traditionally fed a pelleted diet to birds. The quality of pellets must be taken into account also because feeding pelleted rations is not enough to ensure enhanced performance of poultry but also the proper growth, immunity and health status of the bird. There are a number of excellent methods to objectively measure and record the quality of pellets during the manufacturing process.

Other disadvantages of poorly formed pellet includes:

Dusting potential
Flow properties and proportioning gets impaired by fines
Remainders in silos, bins and pans will be increased by fines
Fines and dust are preferred nutrients and habitats for germs and micro organisms of any kind

High fines in the pellet can be a menace and mainly attributed to the issues of “soft pellets” at the press. Improving pellet hardness or durability is an effective means of reducing fines. Pellet durability may be improved by manipulation of diet formulation and improving feed manufacturing practices. Feed manufacturing practices adjusted to suitable to ambient climatic conditions and native ingredients will have a profound effect on pellet durability and potentially involve less expense than changing raw materials or using pellet binders.

Further the economic aspect of moisture retention in feed processing is strongly recognized but there are several other interesting aspects attached with this moisture content of the feed as well. One of them is its consequence on keeping quality and duration for how long it stays fresh. Nothing beats a freshly cooked meal, and this holds true not only for humans, but for animals, too.

Feed components start deteriorating as soon as they undergo the feed mixing process. Feed exposed to high temperature (and) or high humidity, or feeds containing increased levels of sensitive ingredients, will have a reduced shelf life. Cooked starch starts looking “stale” as soon as it cools down, Vitamins starts loosing potency almost instantly when intermixed with certain trace minerals, fats and lipids start oxidizing as soon as they come into contact with air and this is why it is important to control water activity (a_w) of feed to keep these vital nutrients intact and keep the feed remain fresh till it is consumed. It is not that feed becomes unsuitable to consume so fast but it is the significant loss of micronutrients from mixing of feed to actually consume by the hyper producing birds.

Respiratory Challenges/ Ascites:

Because of poor pellet quality and reduced hardness, fines up to 50% have been reported from the field conditions. These incidences of high levels of fines in the field are not only associated with poor live weight and FCR but also has huge dusting potential posing respiratory challenges. The fines in the feed are inhaled by the birds and while exhaling they settle in various part of air sacs, specially thoracic air sac where air stays for longer period which leads difficulty for birds to breath hence deficiency of oxygen in the blood.

Further mold spores appear almost immediately within 12-24 hours after the bagging of the feed in field conditions. The moisture content of the feed usually ranges from 10 – 12%, which when exposed to environment and retained in the pans as uneaten leftover for a week or more before it is consumed in automated feed system gets heavily contaminated with mold spores. Birds fed with lots of fines in feed with increasing mold spores infestation and placed in environments contaminated with aerosolized conidia (mold spores) may show significant pathology after only a short duration of exposure.

Anatomy and physiology of the avian lung-air sac system are strikingly different from that of the broncho-alveolar lung of mammals. Avian air sacs are particularly prone to contamination because they are submitted to an airflow that favours particle deposition. Mold spores are small enough, 2-3 μm in diameter, to bypass initial physical barriers and disseminate deeply in the respiratory system.

It has been suggested that the dust created by the fines of the feed and mold appeared in the stale feed get inhaled by the birds during increased number of pecking, leading to irritation and reduced efficiency of the airways. Poor air quality, environment dust and respiratory diseases also impairs the perfusion capacity of chicken lungs, creating an imbalance between oxygen supply and the oxygen required to sustain rapid growth thus predispose birds to ascites by causing respiratory damage.

Ascites is a disease, which causes death in poultry apparently because of fluid retention. Ascites is commonly known as “water belly”. There is no known cause and no apparent cure. There are theories that the amount of heat in the early days of the chicken or turkey’s life, or stress, may be the cause of ascites but there is no significant data to support these theories. However, invention with antifungal agents to reduce the symptoms associated with ascites and preventing mortality from the disease confirms the role of mold and its spores as a major causative factor for the ascites.

The commercial broiler of today represents the culmination of dramatic changes over the past 60 years. Genetic selection processes that focused mainly on production traits putting heavy pressure on the bird’s cardio respiratory system and immunity.

Increase in metabolic rate, coupled with exposure to environmental conditions such as temperature, lighting and ventilation, and nutritional factors such as feed form or fines into it, all seem to promote the development of ascites. The primary cause of the ascites syndrome, however, is believed to be hypoxia/hypoxemia when the bird’s demand for O₂ exceeds its cardiopulmonary capacity and causes pulmonary hypertension, which results in development of the ascites syndrome. Inadequate ventilation and dusty feed increase the risk of bird exposure to aerosolized spores. Acute cases are seen in young animals following inhalation of spores, causing high morbidity and mortality. The chronic form affects older birds and looks more sporadic.

Crop Mycosis or Mycotic Diarrhea

Crop mycosis or Mycotic Diarrhea is a reference to a condition called Sour Crop that is caused by a type of yeast called Candida albicans. This causes thickening of the crop surface characterized by whitish thickened areas of the crop and proventriculus and may keep nutrients from being properly absorbed from the intestinal tract. It may lead to destroy the tissues of the upper digestive tract particularly the crop and gizzard. It is believed that in severe cases the disease may also infect the intestinal tract. Feeds and fluids may retained in the crop, causing it to enlarge. The orientation of the crop of a chicken is such that any feed or water consumed tends to flow past and contact the crop. Particularly, an environment which is warm, moist, possesses a neutral pH, contains oxygen, includes a substrate which enhances yeast growth.

Poultry of all ages are susceptible to the effects of this organism. The disease affects primarily broilers, laying hens and turkeys. Mycosis is transmitted mainly by ingestion of the moldy feed, water or environment. The organism grows especially well on corn-based diet, so infection can be introduced easily by feeding stale feed. Crop Mycosis may also be “triggered” by the use of high levels of antibiotics in feed or drinking water for treatment of other bacterial diseases like CRD, Necrotic enteritis, colibacillosis etc. Continued use of antibacterial agents in poultry to prevent and treat increasing bacterial infections often causes secondary fungal infection, giving chance to mold spores appeared in the feed during transit and storage to colonize and multiply in the crops as feed stays longest in the crop (approximately 90-100 minutes). Birds/flocks who have been on antibiotics for a period of time are the easiest target of crop mycosis, fed on caked or stale feed.

This malady produces no specific symptoms. Young chicks become listless, pale, show ruffled feathers and appear unthrifty. Affected caged layer hens become obese and anemic. Clinical signs include dull and depressed look, reduced feed intake, poor growth often with large fluid filled crops and foul smelling odor emitted around the mouth. Profuse diarrhea may be noted. Losses are due to reduced feed efficiency, increased mortality (from 5%-20%), poor performance and stunted growth. Some birds also exhibit a vent inflammation that resembles a diarrhea-induced condition having whitish incrustations of the feathers and skin around the area. Feed consumption may increase by 10% to 20%.

Diagnosis is based upon clinical signs and relevant history. Gross lesions are mostly confined to the crop, proventriculus and gizzard. The crop and proventriculus have whitish thickened areas that are often described as having a “turkish towel” appearance.

Erosion of the lining of the proventriculus and gizzard is commonly observed, as well as an inflammation of the intestines. Mycotic lesions in young poults and chicks may be so small as to be easily over- looked during postmortem examination. Additional tests such as crop histopathology or microscopic examination of crop smears (mixed with KOH 10% and heated) will diagnose if Fungi is the cause however are rarely done due to time and financial constraints.

Once introduced into the flock, mold/yeast is perpetuated by suboptimal management conditions. Preventative measures include the continual use of a feed preservative & mold inhibitors in the feed, proper feed handling and storage, daily cleaning and sanitizing of the watering system.

Mycotoxins & Toxicity:

Mycotoxins are often accumulated in the feed dust as they offer a very favourable condition for mold and fungus to grow and exposure to it can have toxic effects on all farms animals including Poultry. Consumption of mycotoxins-contaminated feed causes a plethora of harmful responses from acute toxicity to many persistent health disorders with lethal outcomes. Effects of a mycotoxin on poultry depend on the mycotoxin type, level and duration of exposure and age. Acute toxicity is caused by intake of high doses of mycotoxins and is characterized by death and well-described clinical signs. Most prevalent Aflatoxins are reported to cause reduced bird performance, lower immunity, organ damage, and reduced egg production. Therefore, the main task for feed producers is not only to carefully select raw materials based on the nutritional quality, safety, price, and availability but to also minimize the concentration of mycotoxin in formulated final feed by applying right processing knowledge and strategies aimed at minimizing the risk of fines in final bagging and mycotoxin effects on animals and human health. Challenging climatic conditions characterized by high relative humidity, high temperatures, and more free water in the final feed aggravate the mycotoxins biosynthesis by toxigenic fungi in the feed with high fines percentage.

Conclusion:

Although improved broiler performance is an advantage for pellet feeding, some disadvantages seem to be connected to feeding poor quality pellets to the birds. With respect to animal health, a correlation between poor quality pellet feeding with lots of fines in it and the occurrence of certain diseases cannot be ignored. Nutritionist plays an important role in poultry industry to achieve the genetic potential of these hyper performing birds. As the industry has always been working from a feed formulation perspective and Nutritionist’s and feed manufacturers spend much time and effort in evaluating the formulation, and feed additives but the final pellet quality.

It is important to realize here that feeding low quality pellets or crumble to the “new and improved” poultry can potentially do irreversible damage. Since poultry have the highest rate of gain early in life, they need nutrient-dense diets that support the rapid growth rate without challenging their health status. Feeding for least cost without focusing quality of crumbles and pellet in the first two weeks can result in lost performance that is never regained.

Not only is a proper nutritional program critical, but also a strong quality control program is a must to assure that quality ingredients are received and high-quality feed produced. This is as important for macro-ingredients such as corn, soybean, fat and animal proteins sources as it is for micro-ingredients such as vitamins, amino acids and trace minerals. It is also crucial to ensure that the feed mill delivers durable pellets and crumbles with a minimum amount of fines to encourage feed consumption.

Properly formulated feeds are worthless if birds do not eat the feed as a complete meal packet (a pellet or crumble). Finally, as the number of disease outbreaks are on rise and use of antibiotics for bacterial challenges is becoming limited, it is important for the vets as well to explore alternative options to keep the feed fresh and pathogen free to offset disease challenges.

Feed formulation no doubt is the focus point of this business, but raw material handling and feed processing plays a huge part on feed quality, and hence the performance & bottom line. A correct and pro-active approach will help save the industry much monies from unnecessary wastage from raw material quality, contamination, the unnecessary use of feed additives, over-formulation to compensate for the nutrient loss in feed processing and post processing quality issues, plus the avoidable use of medications at farm level. Controlling water activity (a_w) values of the poultry feed, within safer limit, could be an extremely important consideration, in order to produce a safe and hygienic feed that is both commercially viable and since it plays an effective role in the physical, chemical and biological stability of the product.

About the author:

Dr Naveen Kumar, B.V.Sc & A.H (Gold Medalist), M.V.Sc (IVRI, Bareilly) is a food & oil seed grains storage specialist and a finished feed quality expert for Asian and other tropical countries. He also Business Director of Delst Asia and is located in Faridabad, India. He can be reached at naveensharma21@gmail.com, Mobile +91 93502 89123.

Title Image Source: BG-Studio Shutterstock.com

Another article by author: Introducing Water Activity As A Measure For Feed Quality Control (Part 1)

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16 min read

Water Activity as a Measure for Feed Quality Control: Part II

Food safety is one of the main buzz in the present time. As of now food safety was limited to only human and pet food with little concern of livestock feed. But with time now consumers are not only becoming more aware of the quality aspects of livestock rearing but also on the quality of inputs being fed to reared poultry & cattle. One important aspect of prepared feed quality is the stability of the final product.

Changes in physical, chemical or microbiological properties of feed can be considered loss of stability. Water activity (A_w) is one of several important parameters that affect stability of livestock feed. Water activity is a measure of the free moisture in a foodstuff. It is also defined as the quotient of the water vapor pressure of the substance divided by the vapor pressure of pure water at the same temperature.

The water activity scale extends from 0 (bone dry) to 1.0 (pure water) but most foods have a water activity level in the range of 0.2 for very dry foods to 0.99 for moist fresh foods.

Water activity need not to be confused with moisture content. Moisture content is the combination of free and bound moisture. Free moisture can be explained as water that is available to participate in physical, chemical and biological reactions.

Water activity plays a vital role in the microbial stability of ingredients and final livestock feeds. Bacteria, molds and yeast require water for growth; and every microorganism has a minimum water activity below, which it will not grow.

In the previous part, we discussed the Water Activity stability in terms of degradative reactions rates and microbial growth limits as a function of water activity along with different scenario of damages due to uncontrolled water activity. This is the concluding part of the article.

Storage of soymeal in bulk warehouse

Water activity may affect physical properties such as moisture migration, texture and etcetera.

Moisture migration occurs when there is a aw difference between components or with the surrounding environment as the system comes to an equilibrium. Undesirable textural changes can result from moisture migration in multicomponent product. Water migrates from region with high aw to region with low aw until an equilibrium of aw is achieved but the rate of migration depends on structure or diffusion process (o’Connor et al., 2017). Effect of moisture migration with humidity on aw can be illustrated in moisture sorption isotherm as shown in Figure 7. Figure 7 shows how aw changes as water is adsorbed into and desorbed from a product at equilibrium relative humidity and constant temperature. In practice, this moisture sorption isotherm maybe impractical to use as it is complex and unique for each product. Besides, the relationship between moisture content and water activity changes when temperature varies and also when there are any variations in material composition with a modifying effect.

Figure 7. A schematic representation of a sorption isotherm with a hysteresis between the adsorption and desorption isotherms (Airaksinen, 2005). — Figure 7. A schematic representation of a sorption isotherm with a hysteresis between the
adsorption and desorption isotherms (Airaksinen, 2005).

Water activity affects the biochemical reactions and physical properties of the product.
Uncontrolled a_w in soybean meal (SBM) storage can cause non-enzymatic browning reaction during processing and moisture migration in the storage. Due to moisture migration, it leads to caking of SBM in storage. Besides, water activity has the ability to influence both the rate and color of non-enzymatic browning reaction, which is also known as Maillard reaction. Maillard reaction (MR) is a biochemical reaction between reducing sugars and amino acids to form Maillard reaction products (MRP) and further progress to Advanced glycation end products (AGEs). MR takes place even at room temperature but at a slower rate. The rate of reaction increases when time and temperature increases, and at a humidity of 40-70%. MR is mostly responsible for the deterioration in protein quality, especially lysine is the most susceptible amino acid (Tanaka at al., 1977). SBM is very vulnerable to MR over storage in a hot and humid tropical condition. SBM has high percentage of lysine, arginine, cysteine and tryptophan which easily react with reducing sugars, resulting in MR and the degradation of amino acids (Ibáñez et al., 2020). Since SBM is widely used as a feed ingredient in feed formula, MR is an unavoidable issue in moist heat feed pelleting process. There are inconsistencies in performance of birds fed with mash and pelleted feed which is highly due to the quality of SBM (Araba and Dale, 1990). A good indicator to determine the degree of MR is the colour change in product. Generally, as water activity approaches 0.70, the rate of Maillard reaction increases. When aw is higher than 0.70, Maillard reaction slows down because the reactants are diluted by too much free water.

Figure 8. Picture on the Left shows caking issue in SBM stored in a flat warehouse. Picture on the Right shows the effect of different stages of Maillard reaction in SBM.

Shipment of corn gluten meal in containers

A trial was done to monitor the effects of moisture migration and aw in corn gluten meal (CGM) during shipment from USA to the Pacific Rims.

Moisture movement creates stickyness, caking, and mobility issue on mealy material as Figure 12 (Left). However, when aw is controlled, the corn gluten meal has a very different free-flowing characteristic as observed in Figure 12 (Right).

Figure 12. Picture on the Left shows caking in corn gluten meal whereas Right picture shows free flowing corn gluten meal.

What is worst is that aw has increased substantially with free moisture movement, and the material gets moldy upon reaching port. See Figure 13 (Left). The treated CGM prevents free moisture movement, and aw is hence controlled at a safe level maintaining freshness and the original quality at point of loading, shown in Figure 13 (Right)

Figure 13. Picture on the Left shows crusted top layer and mold in corn gluten meal whereas Right picture shows free-flowing corn gluten meal inside the container. — Figure 13. (Left) Crusted top layer and mold in corn gluten meal. (Right) picture shows free-flowing corn gluten meal inside the container.

Quality integrity of palm kernel pellets

This trial was done to investigate the complain of staleness of products from Malaysia shipped in container to Japan and Korea. 2 MT of fresh products from the same production batch was used with 1 MT Control PKE pellets was bagged and another treated 1 MT PKE pellets bagged. All the bags are stacked on pellets and stored at the hottest areas in production for 90 days to simulate a challenge.

After 90 days, the result was astonishing. Figure 13 shows clearly the difference between control and treatment. The control group (Figure 14 Left) look discoloured, with a stale appearance, and without the aroma of PKE. The treatment group (Figure 14 Right) has a very fresh appearance, maintaining its original quality, and still has a strong PKE smell.

This is another classic case of moisture movement and activated aw compromising the chemical stability of the product. Nutrients and lipids are degraded which explains the poor quality of the control group.

Figure 14. Picture (Left) shows the control group with non-treated PKE and Picture (right) shows the treated PKE. — Figure 14. Picture (Left) shows the control group with non-treated PKE and Picture (right) shows
the treated PKE.

Water activity and moisture content in processed poultry pellet feed

A feed trial was conducted to investigate the addition and capturing of water on the processed pellet feed quality, for starch cooking/gelatinization, data shown in Figure 15. To show the effect of working on a program to capturing water, as in getting moisture from water added at the mixer plus microscopic moisture from steam into the feed chemistry. A process addressed as “positive mash hydration” (This is for the sole purpose of starch granule swelling and sufficient degree of protein denaturation). The result in starch gelatinization is later captured by feed imaging, indicating a loss of birefringence.

With the treatment feed, notice the spike on aw after water has been added at the mixer. Interestingly, the finished feed of the treatment group has a higher moisture content, but water activity is lower compared to the control group. The capturing of moisture for the purpose of starch gelatinization which in turn lock up the hydrolyzed water used in the process of starch swelling/cooking indicates the positive chemistry changes of feed processing.

Figure 15. Feed Quality parameters that were recorded during a pelleted feed trial.

Figure 16. Picture on the Left is the control group with aw of 0.68 and moisture content of 10.14%. Picture on the Right is the treatment group with aw of 0.59 and moisture content of 10.86%. — Figure 16. Picture on the Left is the control group with aw of 0.68 and moisture content of 10.14%.
Picture on the Right is the treatment group with aw of 0.59 and moisture content of 10.86%.

Conclusion

Water activity is a critical parameter in controlling the quality of feed and feed ingredient as it is a reliable indicator and predictor of chemical reactions and microbial responses in the industry. This is how we need to manage and control aw with proper grain storage, shipment of feedstuff, feed processing on both pellets and extruded feed, and handling of mash feed. This will dictate how well we face up to the challenges in keeping the quality of grain over storage, and the processed feed in post-production. A proven approach to managing and controlling aw has been established with proven results. Chasing down a moldy problem with mold inhibitors is like attempting to save a building on fire with extinguishers. The building still gets burnt and ravaged.

References:
Ahn, J. Y., Kil, D. Y., Kong, C. and Kim, B. G. (2014). Comparison of Oven-drying Methods for Determination of Moisture Content in Feed Ingredients. Asian-Australasian journal of animal sciences. 27(11). 1615–1622. 10.5713/ajas.2014.14305

Airaksinen, Sari. (2005). Role of Excipients in Moisture Sorption and Physical Stability of Solid Pharmaceutical Formulations.

Araba, M. and Dale, N. (1990). Evaluation of Protein Solubility as an Indicator of Overprocessing
Soybean Meal. Poultry Science. 69. 76-83. 10.3382/ps.0690076.

Gadient, M. (1986). Effect of Pelleting on Nutritional Quality of Feed. Proceedings of 1986 Maryland Nutrition Conference for Feed Manufacturers (USA). 73-79

Jung, H. B., Lee, Y. J. and Yoon, W. (2018). Effect of Moisture Content on the Grinding Process
and Powder Properties in Food: A Review. Processes. 6. 69. 10.3390/pr6060069

Labuza, T.P., McNally, L., Gallagher, D., Hawkes, J. and Hurtado, F. (1972). Stability of
Intermediate Moisture Foods. 1. Lipid Oxidation. Journal of Food Science. 37. 154-159.
10.1111/j.1365-2621.1972.tb03408.x

Leeson, S. (2015). Vitamin Deficiencies in Poultry. MSD Manual Veterinary Manual.

Mathlouthi, M. (2001). Water Content, Water Activity, Water Structure and the Stability of Foodstuffs. Food Control. 12. 409-417. 10.1016/S0956-7135(01)00032-9

Ibáñez M.A., de Blas, C., Cámara, L., Mateos, G.G. (2020). Chemical Composition, Protein Quality and Nutritive Value of Commercial Soybean Meals Produced from Beans from Different Countries: A Meta-analytical Study. Animal Feed Science and Technology. 267, 114531

o'Connor, L., Favreau-Farhadi, N. and Barrett, A. (2017). Use of edible barriers in intermediate moisture food systems to inhibit moisture migration. Journal of Food Processing and Preservation. 42. e13512. 10.1111/jfpp.13512.

Reid, D.S. (2007). Water Activity: Fundamentals and Relationships. In Water Activity in Foods (eds G.V. Barbosa-Cánovas, A.J. Fontana, S.J. Schmidt and T.P. Labuza). 10.1002/9780470376454.ch2

Tanaka M., Kimiagar M., Lee TC., Chichester C.O. (1977). Effect of Maillard Browning Reaction on Nutritional Quality of Protein. In: Friedman M. (eds) Protein Crosslinking. Advances in Experimental Medicine and Biology. 86. Springer, Boston, MA. 10.1007/978-1-4757-9113-6_22

Tapia, M.S., Alzamora, S.M. and Chirife, J. (2020). Effects of Water Activity (a w ) on Microbial Stability as a Hurdle in Food Preservation. In Water Activity in Foods (eds G.V. Barbosa-Cánovas,
A.J. Fontana, S.J. Schmidt and T.P. Labuza). 1002/9781118765982.ch14

Zambrano, M., Dutta, B., Mercer, D., Maclean, H. and Touchie, M. (2019). Assessment of Moisture Content Measurement Methods of Dried Food Products in Small-scale Operations in Developing Countries: A Review. Trends in Food Science & Technology. 88. 10.1016/j.tifs.2019.04.006

Articles Feed & Storage
4
0
21 min read

Introducing Water Activity as a Measure for Feed Quality Control (Part 1)

The water activity scale extends from 0 (bone dry) to 1.0 (pure water) but most foods have a water activity level in the range of 0.2 for very dry foods to 0.99 for moist fresh foods.

Water activity need not to be confused with moisture content. Moisture content is the combination of free and bound moisture. Free moisture can be explained as water that is available to participate in physical, chemical and biological reactions.

Mold can grow at water activity levels as low as 0.61. Types of mold, temperature and water activity play important role in determining growth characteristics like Penicillium roqueforti germinated at 0.82 A_w at 25°C, 0.86 A_w at 30°C and was unable to germinate at 37°C.

Formation of mycotoxins also depends on the type of mold, substrate and storage conditions, which include pH, temperature and water activity. Mycotoxins can be formed on cereal grains such as corn and wheat. Processing temperatures can kill the mold but will not remove toxins that are already formed.

Mold contamination can also occur during storage and transport of raw material. Development of mold during milling or in storage or in transit in raw material/final product can be avoided by maintaining the final water activity under safe level.

Moisture content has been used as a gauge to control spoilage in grain, feedstuffs, and feed stability for many years. Moisture content is, simply, the quantitative amount of water present in a substance or material. It affects the physical properties of the product, for example, density, weight, conductivity, viscosity and others (Jung, Lee and Yoon, 2018). The method to measure water content includes chemical (Karl Fischer titration), spectroscopic, conductivity and thermogravimetric analysis (Zambrana et al., 2019). In this industry, thermogravimetric analysis is commonly used to measure the moisture content, which is generally determined by weight loss upon drying (LOD). However, in this feed industry, a general practice of LOD is to set higher oven temperature of 120ºC – 130ºC which rendered this method to be inaccurate by 1-2% (Ahn at al., 2014). This is another topic which I will not discuss here.

The reason why we need to introduce water activity as a measure is because the moisture content in the system is not a reliable indicator of chemical reactions and microbial responses in feed pellets as it is only a quantitative analysis that determines the total amount of moisture present in the feed. For example, one safe product may contain 12% of moisture while the other containing just 10.5% of moisture may be more susceptible to spoilage.

Water activity (a_w) is a reliable measure for quality control in feed. Water activity was once defined as the amount of “free” or “available” water in a product as opposed to “bound” water. It was easier to conceptualize but failed to define the concept of water activity. The issue is not whether the water is “bound” or “free” but rather how tightly it is “bound” within the system. The correct definition of aw would be the measure of energy status or the escaping tendency of water in a sample. It indicates how tightly water is bound either chemically or structurally. A portion of the total water content in a product is strongly bound to specific sites such as hydroxyl groups of polysaccharides or carboxyl and amino groups of proteins (Mathlouthi, 2001). Water activity (a_w) is expressed as:

It is the ratio of vapor pressure of water in a material (p), in a completely undisturbed balance with the surrounding air, to that of vapor pressure of pure water under identical conditions (po). Equilibrium relative humidity (%ERH) is the relative humidity of the surrounding where material neither loses or gains moisture at a particular temperature (Mathlouthi, 2001). For example, if we assume that the pellets reached an equilibrium with the surrounding air, then it can be said that the a_w of the pellets will be larger or equal to the ERH(%)/100 of air drawn to the cooler. a_w range extends from 0 (bone dry) to 1.0 (pure water).

The commonly used equipment to measure aw is a water activity meter in which can be a benchtop equipment to be used in a lab or a portable equipment to be used in the feed mill. In a pellet feed production, feed samples from the mixer, cooler and the final bagging are collected and the a_w is measured to determine the safety and quality of the feed.

There are several factors influencing the a_w such as temperature, presence of solutes or a combination of both. Water activity is temperature dependent. As the temperature lowers, most products will have a lower a_w. Therefore, it is crucial to measure the water activity of the pellets in an area where there are no temperature fluctuations in the surroundings. Solutes such as sugar or salt present in the system will also affects the aw as they tightly bind with water, reducing the energy status or the escaping tendency of water in a sample (Reid, 2007).

Water activity is one of the most critical parameters in determining the quality and safety of feed. This is because water solubilizes the reactants and increases their mobility in the system, both of which can leads to faster deterioration in terms of feed safety, shelf life, flavor, texture and smell. Being aware of aw in feed is very beneficial in predicting the stability and safety with respect microbial growth, chemical and biochemical reaction rates, physical properties and etcetera. By controlling the water activity, it is possible to predict potential sources of spoilage and infections, maintain chemical stability, Control non-enzymatic and enzymatic reactions rate, optimize physical properties such as moisture migration, texture and etcetera.

Water activity - stability diagram — Figure 1. Stability in terms of degradative reactions rates and microbial growth limits as a function of water activity. Adapted from Labuza at al. (1972).

While pH, temperature and other factors can affect if and how fast organisms will grow in a product, water activity maybe the most significant factor in controlling spoilage. Microorganisms have a limiting aw level below which they will not grow and aw is the one that determines the lower limit of available water for microbial growth. Even at high moisture content, if the energy status of water is sufficiently low, microorganisms cannot utilize the water to support their own growth (Tapia et al., 2020).

Figure 2. Water activity limits for microbial growth examples of products in those ranges. Adapted from Tapia et al. (2020).

Different scenario of damages due to uncontrolled water activity

The “availability” of water in the system affects the rate of biochemical reaction such as nonenzymatic browning, enzymatic reactions, lipid oxidization, nutrients degradation, protein denaturation, starch gelatinization, starch retrogradation and supports microorganism growth (Figure 1). In general, when water activity decreases, the rate of biochemical reactions decreases. Therefore, controlling water activity is crucial in every stage of this industry, starting from grain storage, feed production to animals’ performance.

Feed stored under hot and high/low humidity

In a hot and high humid environment scenario, escaping water molecules gets trapped in the bag of feed increase the aw above 0.70 As the free water molecules condenses on the surface of the feed, the feed will grow moldy, badly degrading the entire bag of feed.

In a hot and low humid environment, the water molecules evaporate from the feed and escape out of the bag. Even though aw will not increase up to 0.70 sufficiently for microbial growth, the loss of moisture in feed will result in feed shrinkage. During this process, the free water molecules also contribute as a solvent to biochemically degrade essential micronutrients and lipids, compromising the chemical stability.

It is not about whether the feed will get moldy that dictates quality and shelf life. It is much more to a moldy problem.

Feed stored under hot and high/low humidity — Figure 3. Picture on the Left shows 50kg bag of feed stored under hot and high humidity environment while picture on the Right shows 50kg bag of feed stored under hot and low humidity environment.

Extruded fish feed stored in humid and poorly ventilated store

Double liner bag does not necessarily offer better protection to feed quality and better shelf life. The heat evaporates water molecules from extruded feed and now the free moisture gets trapped inside the bag. These moving free water molecules act as a solvent to biochemically degrade the micronutrients and lipids, compromising the nutrient and feeding value. The continue releasing of moisture from extruded feed increases the aw above 0.70, in which supports microbial growth, resulting in moldy feed.

Layer mash feed

Minerals and vitamins are highly reactive in heat and humidity. In hot tropical weather condition, once the premix portion (various essential micro-nutrients) is mixed with other raw materials in the production of mash feed, the compounded mash feed becomes a ticking time bomb. Due to activated water activities, essential micro-nutrient starts to degrade the moment it comes off the mixer. Chemical stability of the mash feed has been compromised. Why!

Many do not realize that compounded mash feed after the mixer has aw level ranging 0.70 – 0.75. As the compounded mash feed transit to the farm bin, the hot pounding tropical sun in just one afternoon can greatly instigate more moisture movement from within the feed. This increases in free moisture constantly increase aw, which can usually reach 0.85 by the time the feed reaches the feeding trough, even within 24 hours of transitioning from the mixer, farm silo bin, and to the layer house see Figure 5. Increasing aw first causes bio-degradation of essential micronutrients, life mold proliferation, and activates microbial growth once aw reaches 0.80.

This problem greatly impacts the overall egg quality (shell thickness, shell cuticle, egg yolk, egg white) and layers gut integrity (gut microbiota, digestibility of protein, ammonia/wet droppings issue)

Due to the uncontrolled moisture movement, the rate of biochemical reactions increases, degrading the essential micro-nutrients such as vitamins, trace minerals and amino acids present in the feed. There are many factors which affect the stability of vitamins such as temperature, moisture, pH, oxygen, light, catalyst, inhibitors, interactions with other component, energy and time, shown in Figure 6 (Gadient, 1986). Most vitamins are stable up to three months if they are stored properly, however, once they are mixed with other components such as oxidative trace minerals in the mash feed, they start to lose their potency rapidly when exposed to moisture, air and temperature. Some of the major deficiency symptoms of water-soluble vitamins found in layer is that it affects the egg production, quality and hatchability as well as the growth and quality of chick (Leeson, 2015). Since the effect of deficiency of vitamins in hens are detrimental and vitamins are prone to destruction, quite often than exception, over formulation is a practice in poultry nutrition. Poultry breeder have put in their best recommendations based on genetics requirement with different scenarios. It did not cost much to be over-generous in the past. However, the cost of these essential micronutrients supplements has been increasing over the years. Over-formulation does not guarantee the bioavailability of vitamins to the animals.

Figure 6. Factors causing the loss of vitamin during storage and processing in feed (Gadient, 1986).

To be continued…..

Water activity is a critical parameter not only in controlling the quality of feed but also in preservation and handling of various feed ingredients. Keep watching this space for some interesting stuff next month on raw materials preservation & handling and use of water activity as a measure.

References:
Ahn, J. Y., Kil, D. Y., Kong, C. and Kim, B. G. (2014). Comparison of Oven-drying Methods for Determination of Moisture Content in Feed Ingredients. Asian-Australasian journal of animal sciences. 27(11). 1615–1622. 10.5713/ajas.2014.14305

Airaksinen, Sari. (2005). Role of Excipients in Moisture Sorption and Physical Stability of Solid Pharmaceutical Formulations.

Araba, M. and Dale, N. (1990). Evaluation of Protein Solubility as an Indicator of Overprocessing
Soybean Meal. Poultry Science. 69. 76-83. 10.3382/ps.0690076.

Gadient, M. (1986). Effect of Pelleting on Nutritional Quality of Feed. Proceedings of 1986 Maryland Nutrition Conference for Feed Manufacturers (USA). 73-79

Jung, H. B., Lee, Y. J. and Yoon, W. (2018). Effect of Moisture Content on the Grinding Process and Powder Properties in Food: A Review. Processes. 6. 69. 10.3390/pr6060069

Labuza, T.P., McNally, L., Gallagher, D., Hawkes, J. and Hurtado, F. (1972). Stability of Intermediate Moisture Foods. 1. Lipid Oxidation. Journal of Food Science. 37. 154-159.10.1111/j.1365-2621.1972.tb03408.x

Leeson, S. (2015). Vitamin Deficiencies in Poultry. MSD Manual Veterinary Manual.

Mathlouthi, M. (2001). Water Content, Water Activity, Water Structure and the Stability of Foodstuffs. Food Control. 12. 409-417. 10.1016/S0956-7135(01)00032-9

Ibáñez M.A., de Blas, C., Cámara, L., Mateos, G.G. (2020). Chemical Composition, Protein Quality and Nutritive Value of Commercial Soybean Meals Produced from Beans from Different Countries: A Meta-analytical Study. Animal Feed Science and Technology. 267, 114531

o'Connor, L., Favreau-Farhadi, N. and Barrett, A. (2017). Use of edible barriers in intermediate moisture food systems to inhibit moisture migration. Journal of Food Processing and Preservation. 42. e13512. 10.1111/jfpp.13512.

Reid, D.S. (2007). Water Activity: Fundamentals and Relationships. In Water Activity in Foods (eds G.V. Barbosa-Cánovas, A.J. Fontana, S.J. Schmidt and T.P. Labuza). 10.1002/9780470376454.ch2

Tanaka M., Kimiagar M., Lee TC., Chichester C.O. (1977). Effect of Maillard Browning Reaction on Nutritional Quality of Protein. In: Friedman M. (eds) Protein Crosslinking. Advances in Experimental Medicine and Biology. 86. Springer, Boston, MA. 10.1007/978-1-4757-9113-6_22

Tapia, M.S., Alzamora, S.M. and Chirife, J. (2020). Effects of Water Activity (a w ) on Microbial Stability as a Hurdle in Food Preservation. In Water Activity in Foods (eds G.V. Barbosa-Cánovas,
A.J. Fontana, S.J. Schmidt and T.P. Labuza). 1002/9781118765982.ch14

Zambrano, M., Dutta, B., Mercer, D., Maclean, H. and Touchie, M. (2019). Assessment of Moisture Content Measurement Methods of Dried Food Products in Small-scale Operations in Developing Countries: A Review. Trends in Food Science & Technology. 88. 10.1016/j.tifs.2019.04.006

Previous article by Dr. Naveen Sharma:

Grain Storage Challenges In Hot Weather Conditions

Articles Feed & Storage
3
0
20 min read

Challenges of Grain Storage in Hot Weather Conditions: Part 2

Synopsis: Understanding the role of water activity in maintaining the vital nutrients and protecting it from the microorganisms will be probably the most significant advancement made by poultry feed manufacturers. Water activity (a_w) is one of the most critical factors for determining the quality and safety of feed and grain. It quantifies the amount of “free” water available in materials for use by microorganisms and chemical agents.

To face up to the extremely challenging tropical hot and humid weather condition, maintaining overall grain quality over storage requires an in-depth understanding of the sciences involving

Water activity
Moisture movement
Good silo design and silo management program
Intake grain quality and length of storage.

The first part of the article covered Water activity (a_w), reasons for rot, Bio-deterioration, Moisture migration and Corrosion, Grain respiration, Shrinkage, Fungus and Mold and Insect infestation. This concluding article covers Good Silo Design and good Silo management program, Intake grain quality and length of storage.

About the author:

Dr Naveen Kumar, B.V.Sc & A.H (Gold Medalist), M.V.Sc (IVRI, Bareilly) is a food & oil seed grains storage specialist and a finished feed quality expert for Asian and other tropical countries. He also Business Director of Delst Asia and is located in Faridabad, India. He can be reached at naveensharma21@gmail.com

Silo Design

If space is not a constraint, a practical silo size and capacity is to keep the height of silo as short as economically possible as it can greatly ease aeration and the air flow moving to the top. It is more preferably to have multiple silos with smaller capacity rather than lesser tall silo with huge capacity for the ease to facilitate silo management.

Aeration

Problem with temperature profile within the grain mass and air current movement can be minimised with effective aeration. Aeration is a tool to manage and control grain temperature, equilibrating with ambient temperature. This is needed to control moisture migration, mold contamination, insect infestation and eventually grain degradation.

In cooler environments, aeration is used to blow in cold ambient air to lower grain mass temperature and to suppress insect development and microflora growth. Whereas in the tropics, a good aeration program with a practical knowledge of working with ambient temperature and humidity will help to minimize heat and to equilibrate grain mass temperature within the silo, reducing issues relating to moisture migration.

As moisture migration moves with the natural air current developing from temperature profile within the grain mass, aeration can help in alleviating the phenomena by harmonising grain mass temperature inside the silo.

Silo Aeration — Picture shows the air current flow after implementing with an aeration system in the tropics. Source from https://www.topcropmanager.com/spring-moisture-migration-in-grainbins-20111/

However, more often than not, aeration system is always under-designed in terms of capacity for the tropics, rendering it unable to cope with dispersing heat in the grain mass. It is more challenging to maintain grain quality in the tropics as the relative humidity ranges from 70-90% while the ambient temperature ranges from 23- 42°C within a day. After a hot day from the scorching sun, a sufficient amount of air flow is required to dispel the heat. Air to grain ratio at a minimum of 0.30-0.40 m3/min air per ton of corn (0.25 cfm per bu) is required. However, most aeration system that comes with the silos are frequently supplied with much lower capacity around 0.11-0.13 cfm per bu range.

A good aeration program with a sound practical approach of working with ambient temperature and humidity will help to minimize heat and to equilibrate grain mass temperature within the silo, reducing issues relating to moisture migration.

In colder countries, the relative humidity is lower than 65% with very cold and cool temperature in most part of the years. This does not post much problems, except to aerate ambient cold air to cool and equilibrate the overall grain mass temperature to the center of the grain mass. The concern is a small period during the warmer summer, as there is now the issue of managing the temperature and humidity variance between day and night.

Graph showing effect of temperature and moisture on stored grain. Source from CSIRO Ecosystem Sciences

Roof ventilation is an important aspect in regulating respirated warm air under the roof space and more nos. of roof vents should be provided for silos in warmer regions. Roof vents should be positioned near the peak of the silo as their function is to remove hot air from headspace. With better efficiency of expelling the warm air coming off the grain, a higher volume of external cooler ambient air can be pulled into the roof space of the eave.

It is strongly recommended to install two units of electric extractor fan per silo for rapid extraction of hot respirated air out to the surrounding.

Good intake management (good filling practices and cleaning to rid dust and foreign material) can assist aerating air flow. Air usually flows along path of least resistance within the silo. Dead space is normally formed due to dust and contamination in grains.

It is advisable to not overfill the silo to the brim but up to the second last ring max, and practice coring after fill. This also assist in better air flow from the roof eve, giving sufficient headspace which also helps in providing a better air cushion between the roof space and the top of grain surface. Hot respirate air has to be continuously extracted out to avoid condensation on the underside of the metal roof at night.

Insulated silo wall is a good option but costly. Insulation prevents temperature differential between day and night, controlling temperature profile to minimize moisture migration. There are three types of insulation which is single sheet, double sheet and a combination of double sheet insulation with insulation material.

. Picture showing insulated silo with insulation material. Adapted from https://siloscordoba.com/blog/grain-storage/silo-insulation-systems — Picture showing insulated silo with insulation material. Adapted from https://siloscordoba.com/blog/grain-storage/silo-insulation-systems

Drying and Silo Operation

Drying helps ensures corn moisture to be kept low and uniform within the maximum safety for grain storage. After the drying process, grains should be transferred into a temporary storage silo or a tempering bin to cool them to ambient temperature. Grains that failed to cool sufficiently after drying may cause a heat steeping effect inside the storage silo, leading to moisture condensation and increasing rate of moisture migration in the grain mass.

Picture shows how does a tempering silo works. Source from
https://siloscordoba.com/blog/grain-storage/what-is-a-tempering-silo-and-what-is-it-used-for/

Corn loading

Coring method during grain loading. Source from University of Minnesota Extension

Before loading into the silo, remove dust, fine particles and damaged grains. This eliminates spout lines that decreases the efficiency of aeration. When there are less fines in the grain mass, it is less challenging for storage management as there will be less dead space within the silo, improving air flow distribution and aeration efficiency.

During the loading of grains, there are additional steps for managing fines. Using the center unloading augers to periodically unload some of the grain to remove any remaining fines. This method is often known as coring. When filling, unloading auger is run at least daily or more often to remove the peaked grain, forming an inverted cone with diameter in the range of 5-10 feet. Grains that are removed can be cleaned and mixed with other grain to be putback into the bin.

Mold control begins with moisture control

All the suggested approach (discussed previously) in managing moisture and temperature helps to minimise grain degradation over storage, but moisture migration is still very uncontrollable. This results in corn caking and sweating in the internal wall, leading to mold contamination and grain degradation…Henceforth, the use of mold inhibitors have been a common practice, but always with futile outcome as this is not addressing the root cause of the problem. An effective moisture management program that is able to negate free moisture movement has been proven to contain moisture migration problem in grain storage, hence maintaining the intake quality.

An actual field storage trial on corn storage was conducted, comparing control (with a normal mould inhibitor program) and treatment (with an effective moisture management program). The control was stored for 8 weeks for early feed production use and the treatment corn was stored and stretched to 16 weeks for later feed production use. Both undergoes the same storage program, but the result shows a very significant difference on corn quality at the end of storage. Despite a shorter storage period, the control batch have darkened germ due to mold contamination. As for the treatment corn, the germ still possess a creamy colour, and retaining the original intake quality despite a twice longer storage period.

Left picture shows the control corn stored for 8 weeks. Right picture shows the treatment corn stored for 16 weeks.

With a good moisture management program, the silo wall had minimal caking and corrosion with free flowing and healthy grains after long period of storage of 4-8 months. Controlling moisture migration is an effective approach to lock in water activity at a safe level, preventing microbial growth and hence keeping intake grain quality.

Left picture shows minimal to no caking and no corrosion to the internal silo wall. Right picture shows free flowing corn of intake grain quality after long period of storage.

Financial loss

The first stage loss is moisture loss due to moisture migration. As moisture migrate, air currents developed from temperature profile. The moisture would accumulate on grain surface and evaporates as weather gets hotter or during silo management program. On average, a minimum of 0.5% of moisture is lost with proper silo management, but if it is not managed properly, moisture loss can go up to 1-1.5%. With the current corn’s price, it will cost approximately US$ 1.50-3.00 per ton of corn stored due to moisture loss.

The second stage loss is when silo management is not properly implemented where ventilation fails to remove free moisture. The three main losses in this stage are the loss of carbon, reduced metabolizable energy and heat damage in grains due to mold contamination.

Left picture depicts different level of heat damage in corn. Right table portrays different parameters that are affected by mold and heat damage in corn — Left: picture depicts different level of heat damage in corn. Right table portrays
different parameters that are affected by mold and heat damage in corn

The third stage of loss is when moisture migrate, causing the corn kernels to dry and their surface becomes brittle. When this occurs, there is a risk of corn fragmentation as grains move in the silo. This will increase the chances of insects and mite infestation. Mite and insects cause physical and nutritional damage to the corn and eventually damaging the livestock production as the presence of mites will cause feed rejection and thus feed wastage and the loss of animal performance.

Left picture shows corn infested with mite and insects. Right table portrays different parameters that are affected by insect and physical damage.

The total amount of loss is alarming. As much as $22.00 per ton of corn is lost in the formulation process. The losses above have yet to include financial impact on farms whereby even minimal mite infestation is able to negatively affect the feed conversion ratio. If losses of nutrients and insect damage are not tackled at source, expensive additives are used to compensate nutrient deficiencies and mask health related problems.

Conclusions

The benchmark to gauge a successful grain storage program is to observe the remaining corn at the bottom of silo after gravity unloading. Ideally, the germ should have a creamy appearance. If the germ area is discoloured even to a slight shade of grey, this is a sign of failed grain storage program. There should also be no visible sign of caking and sweating patches on the side wall. Negligible insect infestation is also a good sign.

The damaging consequence of fungal contamination, loss of nutrients, lost metabolizable energy value of grains greatly impacts feed quality, animal performance and a great economic loss.

All the suggested proper silo engineering set up and silo management practices is to minimize damage if there is a need for long period storage. A proven chemical approach in reducing moisture migration with good aeration management can greatly confine moisture challenge to preserve intake grain quality under the most challenging weather. It is important to control water activity to reduce microorganism activities and degradation of grain. Addressing a pending mold issue with a mold inhibitor treatment is not the answer to keeping grain quality.

The grain and feed industry loses millions of dollars yearly from damaged grain, weight shrink, lost and undigested nutrients, and costs incurred in the attempt to disguise or neutralize problems associated with grain degradation. Much of the repair costs can be cut down if proactive decision is taken to minimise the damage. Proper corn storage management with an effective program will greatly maintain the intake quality and minimise losses.

Featured Silo Image photo created by standret – www.freepik.com

References
Afsah H., Leili S., Jinap, S., Hajeb, P., Radu, S. and Shakibazadeh, Sh. (2013). A Review on Mycotoxins in Food and Feed: Malaysia Case Study. Comprehensive Reviews in Food Science and Food Safety. 12. 10.1111/1541-4337.12029.
Atanda, S.A., Pessu P. O., Agoda S., Isong I. U., Adekalu O. A., Ehendu M. A. and Falade T. C. (2011). Fungi and mycotoxins in stored foods. African Journal of Microbiology Research. 5(25). 4373-4382. 10.5897/AJMR11.487
D'orazio, M. (2012). Materials prone to mould growth. 10.1016/B978-0-85709-122-2.50012-7.
Mathlouthi, M. (2001). Water Content, Water Activity, Water Structure and the Stability of Foodstuffs. Food Control. 12. 409-417. 10.1016/S0956-7135(01)00032-9
Tapia, M.S., Alzamora, S.M. and Chirife, J. (2020). Effects of Water Activity (aw) on Microbial Stability as a Hurdle in Food Preservation. In Water Activity in Foods (eds G.V. Barbosa-Cánovas, A.J. Fontana, S.J. Schmidt and T.P. Labuza). 1002/9781118765982.ch14
Yasothai R. (2019). Storage Losses in Feed Ingredients by Insects and its Control. International Journal of Science, Environment and Technology. 8(1). 44-49.

Previous Part : Water activity (a_w), reasons for rot, Bio-deterioration, Moisture migration and Corrosion, Grain respiration, Shrinkage, Fungus and Mold and Insect infestation

Articles Feed & Storage
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Grain Storage Challenges in Hot Weather Conditions: Part 1

Synopsis: Understanding the role of water activity in maintaining the vital nutrients and protecting it from the microorganisms will be probably the most significant advancement made by poultry feed manufacturers. Water activity (a_w) is one of the most critical factors for determining the quality and safety of feed and grain. It quantifies the amount of “free” water available in materials for use by microorganisms and chemical agents.

About the author

Dr. Naveen Kumar

Dr Naveen Kumar , B.V.Sc & A.H (Gold Medalist), M.V.Sc (IVRI, Bareilly) is a food & oil seed grains storage specialist and a finished feed quality expert for Asian and other tropical countries. He also Business Director of Delst Asia and is located in Faridabad, India. He can be reached at naveensharma21@gmail.com.

To face up to the extremely challenging tropical hot and humid weather condition, maintaining overall grain quality over storage requires an in-depth understanding of the sciences involving:

Water activity, Moisture movement
Good silo design and good silo management program
Intake grain quality and length of storage.

This article focusses on Water activity (a_w), reasons for rot, Bio-deterioration, Moisture migration and Corrosion, Grain respiration, Shrinkage, Fungus and Mold and Insect infestation.

Charting Water Activity in Silos

Over the entire storage period, good quality grain will continue to degrade in quality. Grains degrade 10 times faster in the tropics due to the very adverse weather condition posed by hot scorching afternoon sun, the occasional burst of rain, high humidity and temperature difference between hot days and cold nights. At best, proper grain storage management can only help minimise the damage.

It only takes about 2-3 weeks for an onset of the many negative elements to start degrading the stored corn, and thereafter, rapidly worsening over time. Degradation in grain quality relates to nutrient degradation, bio-degradation, insect and mite infestation, physical structure damage, mold contamination and grain respiration, which leads to weight or moisture shrink. All these damaging losses has an economic impact and cannot be taken lightly.

What actually starts the rot?

Water activity (a_w)

The most important property of water in food systems is the water activity (a_w) of food. Water activity is the ratio of the vapor pressure of water in equilibrium with a food to the saturation vapor pressure of water at the same temperature. The water activity of a food describes the degree to which the water is “bound” in the food and hence its availability to act as a solvent and participate in chemical or biochemical reactions and the growth of microorganisms. It is an important property that can be used to predict the stability and safety of food with respect to microbial growth, rates of deterioration, chemical and physical properties (Mathlouthi, 2001).

At a_w of 0.70 and above, mold starts to grow which inflicts great damage to the grain quality. The water activity and the propensity for mold growth increases with temperature (Tapia et al., 2020). Shelled corn can be safely stored for a year at a moisture content of 13% and a temperature of 10℃. However, the same corn stored at 32℃ can be substantially be damaged by mold within 2 months. This is why it is so much easier to store grains in the cold regions but extremely challenging in tropical regions.

Bio-deterioration

The inherent enzymes present in the seed causes bio-deterioration. The extent of deterioration depends upon the rate of enzyme activity, which is affected by free water and temperature. Biodeterioration results in degradation of nutrients and contamination with anti-nutritional factors.

Nutritional impairment in degraded corn during storage is of great consequence to the health, nutrition and performance of the animals, while directly affecting the profitability of an organization.

Moisture migration

This is the spark that starts the fire and all other problems we face with grain degradation. Moving free water that leached out of grains is the primary cause of grain degradation. This is a natural phenomenon due to the huge temperature difference between day and night throughout the storage period. The difference in temperature causes moisture to move from a region of higher temperature to lower temperature. Moisture will start to migrate if the difference of temperature variance is more than 5℃. The movement of free water is further assisted by convective air current flow inside the silo. This convection air flow moves free moisture to localise spot, and consequently increases water activity, promoting mold growth, insect, and mite infestation.

As steel is a good conductor of heat, the silo wall is easily affected by weather conditions, impacting grain temperature nearer to the wall.

In a cold weather scenario, the cold temperature outside the silo results in the grain and air nearer to the wall to be colder while the center is relatively warmer. This forms a convection air flow that moves downward alongside the wall through the grain. As the air current moves downward and up again through the warmer center, the air starts to warm up from the warm grains and picks up moisture. As warm air rises, it cools because of the colder temperature near the roof, resulting in condensation on the top of grain mass.

In a hot tropical weather scenario, the hot temperature outside the silo results in the grain and air nearer to the wall to be warmer while the center is relatively colder. This forms a convection air flow that moves upward alongside the wall through the grain. As the air current flows upward and down through the cooler center, the air starts to pick up moisture along the passage, leading to moisture condensation towards the bottom silo floor. This phenomenon is most commonly seen in tropical countries, where the silo external surface can be heated to approximately 60℃ in the afternoon and quickly cooled down to about 22-25℃ at night.

Air flow current in Silo — Left picture dictates air flow current in a cold weather scenario while Right picture shows air flow current in a hot tropical weather condition.

Moisture migration occurs quite readily in regions with extreme day and night temperature, as in the Middle East, harsh tropical and equatorial climates. Storing grains at 13-14% in cooler climates is fair game, but however, in hot climates, it is very challenging which involve a totally different approach.

Typically, free water in the grain mass tend to migrate towards the cooler areas in a silo, which is usually the shaded part from the sun, the floor and the lower half of the silo. This is where you will observe sweated patches clinging to the silo wall and at the bottom of silo after gravity unloading.

The increased a_w from moisture migration supports microbial and micro-flora growth, leading to spontaneous heating and eventually causes grain respiration. Heavily contaminated caked layer adhering to the silo sidewall must be properly cleaned and disposed of to control corrosion, contamination in feed production and future seeding of problems.

Corrosion

Corrosion of galvanized steel silos is due primarily to moisture ingress and the consequent degradation of the sweated corn fermenting and producing a complex mixture of chemicals amongst which are formic and acetic acids, both of which are extremely aggressive and damaging on the galvanized coating protection layer, and eventually corroding the unprotected exposed steel surface.

Silo Corrasion — Left picture shows corroded internal side wall of silo. Right picture depicts collapsed silo due to corrosion.

Worst- and best-case scenarios for continued exposure to damp corn predict that the total useful service life of the silos can be reduced by half if corrosion is left unchecked or proper remedial maintenance to the corroded surface is not looked into. Many silos failed because of corrosion and neglect.

Grain respiration

Grain respires once it detects sufficient heat and moisture. This is the reason why feed mills dread storing corn above 14% moisture content. The hot pounding tropical sun with its strong UV rays in the middle of noon will drastically increase the surface temperature of the upper part of silo to a temperature way above ambient temperature. Just like the car roof which gets heated up to a very high temperature from the hot afternoon sun which burns upon touching.

The increase in temperature leads to an increase in respiration rate and consequently shrinkage, especially in the tropics. When grain respire, starch and oxygen are converted to carbon dioxide as well as water and heat, leading to the onset of even more aggressive and uncontrollable respiration.

Shrinkage

Shrinkage is physically noticeable and contributes to financial losses as weight loss in grain storage. However, in addition to weight loss, shrinkage causes irreversible changes to starch molecules, especially to amylose and protein matrixes that encapsulate individual starch granules within the endosperm of the corn kernel.

Depending on the grain intake moisture and storage time, moisture shrink can range from 0.5-3.0%, which is a substantial weight loss.

Moisture loss causes starch retrogradation, which limits digestibility and nutrient availability to the animal. This is an important factor why animal fed with fresh high moisture corn performs better than old dry corn. Shrinkage of corn due to moisture loss also has a negative impact on feed pelleting, since less moisture is being relayed to the compounded meal, resulting in poor steam conditioning and cooking of starch, a low degree of starch gelatinization and hence affecting the overall pellet quality.

Fungus and Mold

Fungus refers to a group of unicellular or multicellular organisms, which feed on organic matter. It includes mold, mushrooms and yeast. Fungus that are usually involved in deterioration of grain have been classified as field fungi, storage fungi, and advanced decay fungi depending on the time of their invasion and colonization of grains before or post-harvest (Afsah et al., 2013). Mold, are multicellular microscopic fungi, typically characterized by the presence of hyphae filaments. Their life cycle is divided into four phases: sporulation, germination, hyphal growth (vegetative growth) and reproduction. The spore stage is where a mold is dormant, allowing mold to endure harsh environments such as extreme temperature and dry conditions. Once mold spores obtain adequate nourishment and moisture, they will germinate and form hyphae. From this time onwards, fungi metabolize the grains by extracting the necessary nutrients and retaining moisture needed for growth, which ultimately poses a biosecurity threat to feed and animal (D’orazio, 2012).

In tropical conditions, Aspergillus spp. are prolific storage fungi in grains as it favours hot conditions with 13-20% moisture and relative humidity of 65-90% depending on the species. They can spontaneously produce heat up to 55°C, resulting in spontaneous heating in grain mass (Atanda et al., 2011). These molds are abundant in the environment and present on all corn kernels surface. It is important to control moisture and water activity to prevent mold proliferation and its damaging consequences. This mold is also often associated with granary weevil activities, which is usually an issue in long period storage.

Mold is a living organism and its growth is influenced by moisture, temperature, oxygen, and substrates. Moisture is the most critical among these factors. Mold unable to grow when the moisture in grains is less than 12%. When the moisture is increased above 12%, molds will start to germinate and grow. Molds proliferate when moisture is above 17% (D’orazio, 2012). Humidity affects grain moisture which makes it extremely challenging to store corn in bags or bulk in an open warehouse.

Molds not only produce mycotoxins but also damage and reduce the nutritional value of grains. Actively growing molds utilise carbohydrates present in grains to produce carbon dioxide, water and heat, leading to reduction of energy value and nutrients degradation of grains or feed.

It is difficult to control fungal contamination in well-dried shelled corn of 13-14% moisture, stored in a steel silo or as bags in a warehouse in tropical condition. Insect infestation due to moisture migration can also further contribute to temperature rise in grains. The combination of mold contamination and insect infestation increases water activity, resulting in an increase rate of mold growth. If mold growth is not controlled, the degradation of corn continues as the storage duration prolongs. There is simply no end to all of these issues if there is uncontrolled moisture migration and grain respiration since both generates an excessive amount of free water, increasing the water activity.

Insect infestation

Insect infestation is a greater problem in regions with high relative humidity while temperature has the greatest influence on insect multiplication. At approximately 32°C, the rate of multiplication is monthly compounded exponential increase of fifty times the original amount (Yasothai, 2019).

Growth of insect, pests and molds raises both temperature and moisture. Insect infestation is rampant whenever there is heavy sweating in areas where corn layer adheres to the silo wall in patches. Naturally, insects will start to breed and incubate their eggs in a conducive environment which provide a rich food source for its young larvae.

The concluding part of the article will focus on Good Silo Design and good Silo management program, Intake grain quality and length of storage.

Featured Silo Image photo created by standret – www.freepik.com

References
Afsah H., Leili S., Jinap, S., Hajeb, P., Radu, S. and Shakibazadeh, Sh. (2013). A Review on Mycotoxins in Food and Feed: Malaysia Case Study. Comprehensive Reviews in Food Science and Food Safety. 12. 10.1111/1541-4337.12029.
Atanda, S.A., Pessu P. O., Agoda S., Isong I. U., Adekalu O. A., Ehendu M. A. and Falade T. C. (2011). Fungi and mycotoxins in stored foods. African Journal of Microbiology Research. 5(25). 4373-4382. 10.5897/AJMR11.487
D'orazio, M. (2012). Materials prone to mould growth. 10.1016/B978-0-85709-122-2.50012-7.
Mathlouthi, M. (2001). Water Content, Water Activity, Water Structure and the Stability of Foodstuffs. Food Control. 12. 409-417. 10.1016/S0956-7135(01)00032-9
Tapia, M.S., Alzamora, S.M. and Chirife, J. (2020). Effects of Water Activity (a_w) on Microbial Stability as a Hurdle in Food Preservation. In Water Activity in Foods (eds G.V. Barbosa-Cánovas, A.J. Fontana, S.J. Schmidt and T.P. Labuza). 1002/9781118765982.ch14
Yasothai R. (2019). Storage Losses in Feed Ingredients by Insects and its Control. International Journal of Science, Environment and Technology. 8(1). 44-49.

Tag: Dr. Naveen Kumar

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Respiratory Challenges/ Ascites:

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Mycotoxins & Toxicity:

Conclusion:

Water Activity as a Measure for Feed Quality Control: Part II

Introducing Water Activity as a Measure for Feed Quality Control (Part 1)

Water activity is a critical parameter not only in controlling the quality of feed but also in preservation and handling of various feed ingredients. Keep watching this space for some interesting stuff next month on raw materials preservation & handling and use of water activity as a measure.

Challenges of Grain Storage in Hot Weather Conditions: Part 2

Featured Silo Image photo created by standret – www.freepik.com

Grain Storage Challenges in Hot Weather Conditions: Part 1

Featured Silo Image photo created by standret – www.freepik.com

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