High dietary inclusion levels of phytase in grower-finisher pigs

Increasing levels of phytase above commercial levels (500 FYT/kg) in pig diets has demonstrated improvements in performance beyond that of a phosphorus (P) adequate control. The aim of this study was to determine the effects of adding increasing levels of dietary phytase to diets with reduced P and calcium (Ca) levels on grower and finisher pig performance, and P and Ca digestibility. Three hundred and eighty four pigs (Large White x Landrace dam to Hampshire boar) were allocated to trial at 35.3 (± 4.92) kg live weight. Pigs were fed one of six diets (eight replicates per treatment), a positive control diet (PC) containing 0.56% total P and 0.65% total Ca from 35-55 kg (grower stage) and 0.52% total P and 0.60% total Ca from 55 to 110 kg liveweight (finisher stage), a negative control diet (NC) containing 0.46% total P and 0.53% total Ca (grower stage) and 0.41% total P and 0.48% total Ca (finisher stage), NC+250, NC+500, NC+1,000, NC+2,000 phytase units FYT/kg. There was no difference in performance between the dietary treatments during the grower stage, however increasing phytase linearly improved P (P < 0.001) and Ca (P < 0.05) digestibility. Throughout the finisher stage phytase increased feed intake (linear, P < 0.001), ADG (quadratic, P < 0.05) and tended to improve feed efficiency (linear, P = 0.058). Pigs fed the PC diet grew faster than pigs fed the NC diet (P < 0.001). Phosphorus and Ca concentration in the metacarpal bone increased linearly with the addition of phytase (P <0.01; P < 0.001). In conclusion, increasing levels of phytase above 250 FYT/kg in finisher pigs linearly improved performance.