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 v arieties of wheat, including the effects of supplemental microbial phy tase, were studied in three experiments with pigs. Feedstuffs were ble nded into a basal diet low in P, aiming at providing a suboptimal P su pply to pigs. The digestibilities of P contained in barley, soybean me al, and wheat were calculated using the difference method. Growing pig s 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, aft er 7 days of adaptation, excreta were quantitatively collected for 8 d ays. The digestibility of P in barley and soybean meal was 45 and 31%, and was significantly increased to 66 and 73%, respectively, by suppl emental microbial phytase. In wheat, the digestibilities ranged betwee n 61 and 74%, depending on the variety under study. No clear connectio ns between P digestibilities and analytical parameters were found. In a mixture of wheat and soybean meal, P digestibilities were additive w hen no microbial phytase was used.