Enzymes in Animal Feed
The first enzymes developed by the biotech industry were arabinoxylans and beta glucanases. Their function was to degrade non-starch polysaccharides, which are the fibrous portions of the grain. These enzymes reduced the viscosity of the non-digested grain in the intestine. The first trials proved that adding exogenous enzymes to wheat-based diets improved digestibility in monogastric animals. These early studies also helped scientists understand the mode of action of these enzymes and enabled them to develop new enzymes capable of working on a wider variety of substrates.
At the beginning of the 1990s, the main topic of conversation among nutritionists and researchers was what they considered to be the inevitable decline of sources of phosphorus in animal feed. The additives and supplements industry responded quickly to this challenge by focusing on enzymes capable of releasing more phosphorous through a molecule usually not present in livestock animals: phytate. Fungal phytase was able to chemically break down the phytate, releasing additional phosphorus in feed for pigs and poultry. While the nutritional matrixes of phytase would not be consolidated until 2000, they showed good initial values of 0.05 phosphorus and a maximum of 0.10 percent available phosphorus.
When feed enzymes were first used over a decade ago, their acceptance was limited to phytase applications for reduced phosphorus excretion. Although feed enzymes have been utilized for many years, we have only scratched the surface of research on feed enzyme technology.
The greater understanding of feed enzyme use comes at an ideal time as the demand for high-quality protein across the Globe continues to rise. With advancements in management and technology, animals are in production for a relatively short time. Producers must maximize that time efficiently to meet increased protein requirements, including getting the most out of the feed.
Producers need to get smarter about sustainably optimizing animal production — and enzymes offer an opportunity to do that.
Animal feed is the most significant cost item in livestock and poultry production, accounting for 60-70% of total expenses. To save on costs, many producers supplement feed with enzyme additives, which enable them to produce more meat per animal or to produce the same amount of beef cheaper and faster.
Found in all living cells, enzymes catalyze chemical processes that convert nutrients into energy and new tissue. They do this by binding to substrates in the feed and breaking them down into more minor compounds. Enzymes can be classified by the types of substrates they work on. For instance:
Proteases break down proteins into amino acids.
Carbohydrates split carbohydrates into simple sugars.
Lipases separate lipids into fatty acids and glycerol.
Commercially-available enzymes can be derived from plants and animals (e.g., actinidin from kiwi and rennet from calf stomachs) and microorganisms (e.g., amylase from Bacillus and lactase from Aspergillus).
Enzymes and their modes of action:
1. Phytase
The substrate for phytase is phytic acid, which is how phosphorus is stored in plant tissues. Phytic acid is problematic to the animal because it binds minerals and amino acids, which become unavailable to the animal. This results in beneficial nutrients being excreted into the environment, resulting in a loss in performance.
Phytase enzymes have been added to monogastric diets for more than a decade. As previously stated, phytase’s primary goal and mode of action are to reduce phosphorus excretion, and its use continues to increase due to diet cost savings. The initial savings are associated with reduced dietary phosphorus cost, but nutritionists also have the flexibility to reduce the amount of soybean meal due to improved amino acid digestibility.
2. Carbohydrase
The carbohydrase class of enzymes includes xylanases, glucanases, and amylases. They act in the stomach to break down and degrade carbohydrates such as fiber, starch, and non-starch polysaccharides into simple sugars that provide energy for use by the animal.
Grain sources such as corn, barley, and wheat have hard coatings on the outside. Much of the layer is physically broken up during feed mill processing, but only partially. The fibrous portion of grain cell walls is indigestible, and 10 to 20 percent is getting through. Carbohydrases will attack and degrade these starchy grain molecules.
One of the most common carbohydrates is xylanase. Xylanase attacks the arabinoxylan structure of corn or wheat, allowing the animal to absorb its components as an energy source. This limits the requirement for supplemental fat or energy in the final diet.
3. Protease
Protease enzymes are the newest technology on the block, with animal or vegetable protein as their substrate. They break down anti-nutritional factors associated with various proteins. Proteases improve the digestion of proteins and increase amino acid availability, which helps release valuable nutrients. The result is improved animal growth and performance and minimal adverse effects of undigested protein in the hindgut.
Raw ingredients with low amino acid digestibility respond greatest to an exogenous protease, which is why its most excellent value is when alternative ingredients are used in the diet. Proteases help producers manage the nutritional risks associated with feedstuff quality and allow them to utilize all available feed ingredients best.
Proteases are not limited to diets with alternative ingredients. Animals consuming a traditional corn-soybean meal diet cannot utilize 100 percent of the protein fraction. Therefore, adding a protease enzyme to a corn-soybean meal diet will enhance amino acid digestibility and animal performance.
Benefits Of Enzymes In Animal Feed
Even though some segments of the pig and poultry industries still do not use exogenous enzymes, the growth of the enzyme market has been substantial. Since enzymes improve the digestibility of plant-based feed ingredients, they offer immediate economic benefits to animal production. Enzymes have allowed producers to enhance further their feed conversion rates, the uniformity of their flocks and herds, and the efficiency of their feed mills since fewer grains must be purchased and processed.
With all these benefits available to producers, the animal nutrition industry is becoming more eager to study enzyme technology further to optimize animal production. Research is ongoing on the effects of degradation of different substrates, different methods of producing enzymes, epigenetic products of enzymes in the formation and development of the intestine, and interaction with the microbiota and intestinal health, as well as their direct or indirect action on the immune system. As our understanding of enzymes evolves, we should expect a revolution in how we feed our animals.
Future Use Of Enzymes In Animal Feed
The benefits of enzymes are becoming better realized as more research is done. For the animal, enzymes optimize gut health, produce consistent growth and enhance overall health. For the producer, they decrease feed costs and improve profitability.
Each type of enzyme has its specific function and therefore does not interfere with one another.
