Shelton Jason, Bidner, Thomas D., Southern, L. Lee, Williams, SB, Johnston, LeAnn, Payne, Rob, Gaston, Lewis A. | 2/24/2005 11:29:22 PM
Phytate is a compound found in many common feed ingredients that decreases nutrient availability in animal diets. The main anti-nutritional effect of phytate is that it makes phytate phosphorus unavailable for digestion and absorption by nonruminants such as swine and poultry. Phytate also has negative effects on digestive enzymes, trace minerals, calcium, protein and amino acids, and carbohydrates.
Phytase is an enzyme that breaks down phytate. Phytase is produced in limited amounts by animals but is commercially available. When added to swine or poultry diets, the levels of phosphorus and calcium can be reduced by approximately 0.10 percent of the diet.
Commercially, the primary use of phytase is to increase the availability of phosphorus, which reduces the amount of inorganic phosphorus added to the feed and consequently reduces the amount of phosphorus in the manure. Swine and poultry producers also can benefit from phytase supplementation in other areas. Phytase has been shown to increase protein, amino acid and carbohydrate availability. Furthermore, by decreasing the amount of protein, amino acids and minerals excreted from swine and poultry, phytase can have positive effects on the environment. However, the positive effect of phytase on the environment must not be overshadowed by a negative effect on animal productivity.
Chicks Gain More Weight
To properly formulate diets with phytase and to realize its full potential, the exact value of the nutrients it releases must be investigated. Recently concluded research projects indicate that the nutrient values for phytase for phosphorus, calcium, amino acids and the dietary components that produce energy can be used in diet formulation for broilers fed from hatch to slaughter with no negative effects on growth performance, carcass traits or meat quality. Also, adding phytase decreases the amount of total and soluble phosphorus in the litter, which has positive effects on the environment when poultry litter is used as fertilizer. Equally important, phytase may reduce the cost of the diet by reducing the amount of soybean meal, fat and crystalline amino acids that must be added.
Research also has indicated that adding phytase to nutritionally adequate diets for young chicks increases growth performance. Chicks fed phytase ate more and thus gained more weight regardless of the nutrient content of the diet. Results from recent research have indicated that the increase in daily feed intake may be explained by an increase in feed transit time (time from ingestion to excretion) in chicks fed diets with phytase.
Phytase has been shown to increase the availability of some trace minerals, including copper, manganese, iron and zinc. Because of the positive effect of phytase on trace mineral utilization, commercial use may lead to removing trace minerals in diets where phytase is added. Research has been conducted on the effect of phytase with and without the trace mineral premix in diets for chicks from hatch to 42 days and in diets for pigs at different stages of growth. The trace mineral premix used at the LSU AgCenter swine and poultry farms contains zinc, copper, iron, manganese, iodine and selenium.
Research results indicate that removing the trace mineral premix from poultry diets from hatch to 42 days has no effect on growth performance, but it does have negative effects on bone strength. This negative effect was not overcome with the addition of phytase, indicating that phytase may not be able to replace the trace mineral premix in diets for broilers.
Phytase Helps Pigs, Too
Researchers found that removing the trace mineral premix and adding phytase to the diets of pigs had no negative effect on growth performance, carcass traits or pork quality. Results also indicated that phytase may have positive effects on quality of retail cuts of pork, because adding phytase (more specifically, reducing inorganic phosphorus levels in diets with phytase) decreased the amount of water lost from dripping, thawing and cooking. Removing the trace mineral premix from nursery pig diets decreased growth performance, and 50 percent of those pigs developed skin lesions. Adding phytase to the diet without the trace mineral premix resulted in growth performance equal to that of the pigs fed the diet with the trace mineral premix. Also, no skin lesions were found on any of the pigs fed either the diets with the trace mineral premix or those with phytase.
This research indicates that phytase may not be able to replace the trace mineral premix in chick diets but that it can replace the trace mineral premix in pig diets.
The effect of phytase on energy and amino acid availability is a much-debated topic. Research results from several experiments have indicated that phytase improves the availability of amino acids, starch and the dietary components that produce energy in diets for growing pigs. Fasting glucose levels also have been increased in growing pigs fed diets with added phytase. This response indicates that phytase increases starch digestibility.
New phytase products are being produced for use in animal agriculture, and one area of research is to evaluate each product to see how they compare with one another. Two of these phytase products are Ronozyme and Natuphos. We have conducted several trials with broilers, using both dry and liquid forms of each product. Our results show little difference in the ability of either Natuphos or Ronozyme to increase phytate-bound phosphorus utilization. Both products, regardless of form, produced similar growth performance in commercial broilers, so the choice of which product to use in diets for swine or poultry can be based on price.
Research at the LSU AgCenter has shown that adding phytase to swine and poultry diets has positive effects on calcium, phosphorus, amino acid, trace mineral digestibility and the dietary components that provide energy. These positive effects can be achieved without affecting carcass composition or meat quality. Furthermore, by taking advantage of all of the positive aspects of phytase, producers can reduce the negative effects of animal waste on the environment (by reducing the nutrient content of manure used as fertilizer) and reduce diet cost by reducing the levels of some of the high-cost feed ingredients.