Feed Additives for Drying Poultry Litter
By David Trott Wallenstein Feed & SupplyFeatures Nutrition and Feed Research Poultry Production Production
Wet litter can directly affect bird health, but there are additives that can be placed in feed to help
In commercial poultry operations, controlling litter moisture is essential to maintaining animal health, welfare and production performance. Poultry litter consists of bedding material, excreta, feathers and spillage, and it also has a dynamic moisture content affected by management, bird health and nutrition. Since the cause of wet litter is multi-factorial, it is critical to constantly monitor heating and ventilation systems to remove the large amount of water excreted into the litter each day.
Changes in water intake and excretion caused by microbial or dietary intestinal challenges can quickly have a major impact on litter moisture. For example, coccidia infections damage the gut directly and can lead to necrotic enteritis and wet litter if not controlled with the use of anti-coccidials in the feed. Diarrhoea and wet litter can also result from intestinal challenges by bacteria Antibiotics can be used to treat bacterial infections and therefore reduce wet litter – however, the focus of this article is to discuss non-antibiotic feed additives when there is a non-specific microbial intestinal challenge.
Dietary intestinal challenges in poultry production are often the result of high-nutrient dense diets formulated to maximize the entire flock’s production. In addition, commercial poultry are tremendously uniform and there is a tendency to over-formulate diets in order to meet the nutrient requirements of the least efficient birds within a flock in order to maintain production. Access to feed and water is essential for each bird to obtain nutrition and maintain water balance, but the dietary intestinal challenges in the most efficient birds can potentially result in more water excretion and wet litter.
Some feed additives are used with the objective of directly drying litter moisture by maintaining water balance of birds. However, most of the feed additives discussed have indirect effects on drying litter through improved nutrient availability and gut health.
The majority of commercial feed formulations contain added enzymes from fungi or bacteria to improve the availability of nutrients and reduce the prevalence of anti-nutrients. Phytase is the most common feed enzyme as it improves the phosphorous, calcium and mineral availability of grains, and may also improve nutrient availability by digesting the anti-nutrient, phytate.
Other feed enzymes, such as xylanase, target fibers of plant cell walls called non-starch polysaccharides (NSPs), which reduce nutrient availability, by increasing gut viscosity or caging nutrients within cell walls. The use of xylanase enzymes when feeding wheat-based diets to poultry is well accepted and essential for reducing gut viscosity. Adding xylanase to corn-soy diets is thought to release the caged nutrients from cell walls, as well as improve gut health by digesting anti-nutrients and providing nutrients that promote a beneficial gut flora.
To promote drier poultry litter with feed enzymes, the nutrient density of poultry diets should be reduced – specifically reductions in crude protein and sodium, which have the biggest impact on litter quality. The challenge with using feed enzymes is to appropriately reduce nutrient density without risking loss in production. According to recent research, it may be viable for a producer to order extra feed enzymes on top of current formulations to dry poultry litter. This “super-dosing” of enzymes may work by removing anti-nutrients and promoting a healthy gut-flora, but this is not currently a common commercial practice.
Clay-based products are typically used as litter amendments for managing poultry litter, but they may also be helpful when fed to poultry. Two products approved for use in feed as pelleting aids include sodium bentonite and diatomaceous earth.
Bentonite, or montmorillonite clay, has a high water absorption capacity and high cation exchange capacity. When used as a litter amendment, sodium bentonite absorbs excess water and prevents caking of the litter. Bentonite added to feed is thought to have the additional benefits of slowing feed passage and improving feed efficiency, and it is approved for use up to 20 kilograms per tonne (kg/t).
Diatomaceous earth is the fossilized remains of phytoplankton or diatoms and is characterized as an adsorbent, anti-caking agent and dewormer. Diatomaceous earth is also sometimes used as a poultry litter amendment to help control fly larvae and darkling beetles, and is well accepted in organic production systems. As a feed additive, diatomaceous earth may also provide the additional benefits of slowing feed passage and improving feed efficiency along with absorbing anti-nutrients and toxins. Similar to bentonite, diatomaceous earth can be used up to 20 kg/t of feed and has been shown to result in poultry excreta with drier consistency.
For clay products, the drier litter is thought to be a result of slower feed passage more efficient absorption of nutrients; however, the high dosage of 20 kg/t could potentially bind nutrients or dilute the nutrient density of the feed too much. The effectiveness of clay-based products drying poultry litter at dosages lower than 20 kg/t is possible, but has not been reported.
Betaine, or trimethylglycine, is a non-essential nutrient named in the 19th century after it was discovered in sugar beets.
It is also naturally occurring in grains fed to poultry, with the highest levels found in wheat. Osmolytes such as betaine affect the water balance or osmotic pressure of cells and tissues by regulating the movement of water through the cell.
When betaine is supplemented in poultry diets, it is quickly absorbed by intestinal cells and balances the osmotic pressure of the gut containing high concentrations of inorganic salts after a meal. In other words, water loss is reduced and the integrity of the intestinal cells is maintained.
Commercial sources of betaine are a by-product of sugar production from sugar beets, and are available as feed additives.
Betaine added at 1 kg/t of feed has been shown to be effective at relieving heat stress in poultry, treating fatty liver disease in layers and treating wet litter in turkeys. Betaine seems to be effective at maintaining intestinal water balance and drying poultry litter when wet litter is a result of over-formulation of nutrients. It has also been shown to reduce the intestinal damage caused by coccidiosis in broilers.
Additives for improving health
Antibiotics added to feed (AGPs) are thought to promote growth of poultry by maintaining intestinal health – therefore, most feed additives that are potential replacement for AGPs must also target gut health. Commercially available feed additives include organic acids, yeast-derived products, direct-fed microbials and essential oils. Many of these feed additives are by-products of other industries and have been commercially available for years for various uses.
Organic acids are naturally occurring, mild acids that have been used for decades as feed preservatives. Acidification of the gut and antibacterial activity of organic acids are thought to promote the growth of beneficial microbes and inhibit the growth of pathogens. Organic acids also quickly dissociate in the high pH of the proventriculus, so the beneficial effect of organic acids in the small intestine of poultry can require either protected sources or used high dosages of organic acid feed additives.
Yeast-derived products contain yeast cell wall fragments, mannan oligosaccharides, which competitively bind gram-negative bacteria and prevent attachment to intestinal cells, which may also promote the growth of beneficial microbes and enhance the structure and function of the gut. Whole yeast products are either specifically grown for use as feed additives or are by-products of other production systems such as citric acid production. Interestingly, dietary yeast from dried distiller’s grain with solubles (DDGS) is already present in commercial poultry diets containing DDGS. However, the effects of purified yeast-derived products on gut health are the most researched.
Direct-fed microbials (DFMs) are beneficial organisms added to poultry feed for the purpose of colonizing the digestive tract. DFMs have been commercially available for the last 20 years, and are commonly used in US layer operations for salmonella control. Common DFMs include heat-tolerant Bacillus and lactic acid producing DFMs, Lactobacillus and Bifidobacterium. In addition to competing for nutrient resources with pathogens, these bacteria produce organic acids that have the same beneficial effects of adding organic acids alone.
Essential oils are aromatic plant extracts that when used as feed additives are actually synthetic derivations with well studied modes of action, which include direct anti-microbial effects, stimulation of digestive enzymes, and improved gut structure and function. Essential oils are not by-products and are therefore likely to be the most recently available gut-health feed additive.
In summary, promoting gut health is an important tool for maintaining dry litter in poultry production systems. Although dry poultry litter is primarily accomplished with proper nutrition and good management of barn heating and ventilation, feed additives can also be useful tools for drying poultry litter when birds have microbial or dietary intestinal challenges.
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