Effects of graded levels of an Escherichia coli phytase on growth performance, apparent total tract digestibility of phosphorus, and on bone parameters of weanling pigs fed phosphorus-deficient corn-soybean meal based diets

An experiment was conducted to evaluate the efficiency of a novel Escherichia (E.) coli phytase on improving growth performance, calcium (Ca) and phosphorus (P) digestibility, and bone ash concentration of weanling pigs fed P-deficient corn-soybean meal based diets. Sixty weanling pigs with an initial body weight of 11.2 ± 1.2 kg were randomly allotted to 1 of 6 dietary treatments with 10 replicate pigs per treatment. The dietary treatments were: 1) positive control (PC), 2) negative control (NC), 3) NC + 250 phytase units (FTU)/kg diet, 4) NC + 500 FTU/kg diet, 5) NC + 1000 FTU/kg diet, and 6) NC + 2500 FTU/kg diet. Pigs were fed phase I diets during the initial 6 days and phase II diets from day 7-27. At the end of the experiment, all pigs were euthanized to collect the 3rd and 4th metacarpals from each front foot. Results indicated that in both phase I and II, pigs fed the NC diet had reduced (P < 0.05) apparent total tract digestibility (ATTD) of P compared with pigs fed the PC diet. However, inclusion of graded levels of E. coli phytase to the NC diet increased (linear and quadratic, P < 0.01) the ATTD of P. No differences were observed in the ATTD of Ca or the ATTD of dry matter as E. coli phytase inclusion increased in the diets. Pigs fed the PC diet had greater (P < 0.05) fat-free dried bone weight (g), bone ash weight (g), bone ash concentration (g/kg), bone Ca (g), and bone P (g and g/kg) and greater (P < 0.05) average daily gain (ADG), average daily feed intake (ADFI), and gain: feed ratio (G:F) during phase II and during the overall experimental period than pigs fed the NC diet. Graded levels of E. coli phytase linearly and quadratically increased (P < 0.05) fat-free dried bone weight (g), bone ash weight (g), bone ash (g/kg), bone Ca (g), and bone P (g). Inclusion of E. coli phytase also increased (linear, P < 0.05) final body weight, ADG, ADFI and G:F during phase II and during the entire experimental period. No differences were observed between diets supplemented with 1000 or 2500 FTU/kg of E. coli phytase for fat-free dried bone (g), bone ash weight (g), bone ash (g/kg), bone Ca (g and g/kg), bone P (g) or final BW, ADG, ADFI, or G:F during phase II or during the overall experimental period. In conclusion, adding up to 1000 FTU/kg of the novel E. coli phytase to P-deficient diets increased growth performance and P utilization in weanling pigs.