SUPPLEMENTING CORN-SOYBEAN MEAL DIETS WITH MICROBIAL PHYTASE LINEARLY IMPROVES PHYTATE PHOSPHORUS UTILIZATION BY WEANLING PIGS

Two experiments were conducted with weanling pigs to determine the effectiveness of a dietary supplement of Aspergillus niger phytase in improving the availability of phytate-P in corn-soybean meal diets without supplemental inorganic P. Experiment 1 consisted of two P and Ca balance trials and two feeding trials. Twelve pigs (8.18 +/- .44 kg BW) were housed individually in stainless steel metabolism cages. Six pigs received 750 phytase units (PU)/g of basal diet and the other six pigs received the basal diet without supplemental phytase as control. In Exp. 2, 96 pigs (8.81 +/- .75 kg BW) were allotted to 16 partially slotted floor pens and their basal diets were supplemented with either 0, 250, 500, or 750 PU/g for 4 wk. Individual pig weights and pen feed consumption were measured weekly. Blood samples were taken from all pigs at the end of each trial in Exp. 1 and from three pigs per pen weekly in Exp. 2 to measure serum (plasma) inorganic P (P) and Ca concentrations and alkaline phosphatase (AP) activities. The results of Exp. 1 indicated that dietary phytase increased P retention by 50% (P < .0001) ard decreased fecal P excretion by 42% (P < .0001). Pigs that received dietary phytase had serum P and Ca concentrations and serum AP activities that were nearly normal, whereas control pigs had values indicative of a moderate P deficiency. Favorable effects of phytase disappeared when the phytase was removed from the diet. The results of Exp. 2 indicated a linear increase in plasma P (P < .001), ADG (P < .07), and ADFI (P < .01) with increased dietary phytase activity. Plasma AP activity decreased linearly with increased dietary phytase activity up to 500 PU/g of diet. Gain/feed and plasma Ca concentration seemed to be unaffected by dietary phytase activity. In conclusion, supplements of Aspergillus niger phytase up to 750 PU/g of feed in corn-soybean meal diets of weanling pigs resulted in a linear improvement in utilization of phytate-P.