Digestibility of phosphorus contained in soybean meal, barley, and different varieties of wheat, without and with supplemental phytase fed to pigs and additivity of digestibility in a wheat-soybean-meal diet

The digestibility of P from barley, soybean meal, and four different varieties of wheat, including the effects of supplemental microbial phytase, were studied in three experiments with pigs. Feedstuffs were blended into a basal diet low in P, aiming at providing a suboptimal P supply to pigs. The digestibilities of P contained in barley, soybean meal, and wheat were calculated using the difference method. Growing pigs initially weighing 30 kg were kept in metabolism crates and fed two times daily at about 2.5-fold energy requirement for maintenance. Each experiment followed the design of a Latin square. In each period, after 7 days of adaptation, excreta were quantitatively collected for 8 days. The digestibility of P in barley and soybean meal was 45 and 31%, and was significantly increased to 66 and 73%, respectively, by supplemental microbial phytase. In wheat, the digestibilities ranged between 61 and 74%, depending on the variety under study. No clear connections between P digestibilities and analytical parameters were found. In a mixture of wheat and soybean meal, P digestibilities were additive when no microbial phytase was used.