Effects of microbial phytase on coefficient of standardized total tract digestibility of phosphorus in growing pigs fed corn and corn co-products, wheat and wheat co-products and oilseed meals

Three experiments were conducted to determine the effects of microbial phytase on the coefficient of standardized total tract digestibility (CSTTD) of phosphorus (P) in corn and wheat and various co-products of these grains and in oilseed meals fed to growing pigs. In Exp. 1, 90 barrows (initial body weight: 39.27±2.22kg) were individually housed and allotted to 1 of 14 cornstarch-based diets based on corn or distillers dried grains with solubles (DDGS; low, medium, or high oil), corn gluten feed, corn gluten meal or corn germ meal with 0 or 500 units per kilogram of microbial phytase (n=6). A P-free diet was used to determine basal endogenous P loss (EPL). The results showed that the CSTTD of P was greater (P<0.05) in DDGS than in corn, corn gluten meal, corn gluten feed or corn germ meal. In Exp. 2, 66 barrows (initial body weight: 38.26±2.19kg) were used to determine the CSTTD of P in wheat, wheat bran, wheat shorts, wheat feed flour and wheat red dog (n=6). Ten diets contained each of the test ingredients with 0 or 500 units per kilogram of microbial phytase and a P-free diet was also formulated. The results showed that there was no difference in the CSTTD of P among wheat and wheat co-products. The addition of phytase increased (P<0.01) the CSTTD of P in all ingredients. In Exp. 3, 66 barrows (initial body weight: 35.02±2.03kg) were allotted to a randomized complete block design with 11 diets and 6 pigs per diet. Ten diets were based on cornstarch and soybean meal, canola meal, cottonseed meal, partially dehulled sunflower meal or peanut meal with either 0 or 500 units of microbial phytase, and a P-free diet was also used. The results showed that the CSTTD of P was less (P=0.03) in peanut meal than in soybean meal, canola meal, cottonseed meal and partially dehulled sunflower meal, but the addition of phytase increased (P=0.03) the CSTTD of P in all oilseed meals. In conclusion, the results of these experiments indicate that differences exist in the CSTTD of P among feed ingredient, and the susceptibility of phytate from corn to phytase attack may be less than that from wheat and oilseed meals.