The effects of phytase on growth performance, carcass characteristics, and bone mineralization of late-finishing pigs fed maize–soyabean meal diets containing no supplemental phosphorus, zinc, copper and manganese

Late-finishing pigs (n=408) with an average initial weight of 84 kg were used to evaluate the effects of supplementing microbial phytase to maize–soyabean meal diets in which sources of supplemental phosphorus (P), zinc (Zn), copper (Cu), and manganese (Mn) were removed. The four dietary treatments employed were: (1) positive-control which included a standard trace-mineral premix and inorganic P supplementation (1.6 g/kg available P, 4.6 g/kg Ca); (2) negative-control in which a trace-mineral premix without Zn, Cu, and Mn was fed, and no inorganic P was added (0.6 g/kg available P, 4.6 g/kg Ca); and the negative-control diet supplemented with either (3) 300; or (4) 500 U/kg microbial phytase. With the exception of available P, Zn, Mn and Cu, diets were formulated to meet or exceed National Research Council (NRC, 1998) nutrient recommendations for late-finishing pigs. Each supplementation regimen was fed to 102 pigs (6 pens of 17 pigs comprising triplicate replicates of both castrates and gilts) from 84 to 123 kg body weight. Removing inorganic P and selected trace minerals, or the addition of either 300 or 500 U/kg phytase to the negative-control diet did not affect (P>0.10) weight gain, feed intake, or feed efficiency. Moreover, carcass characteristics were not affected (P>0.10) by any of the supplementation strategies employed in this experiment. Metacarpal III and IV bone ash weight, however, was reduced (P<0.05) in pigs fed the negative-control diet compared to the fully-supplemented positive-control diet and the diets containing added phytase. These data indicate that supplemental levels of inorganic P, Zn, Cu, and Mn can be reduced or eliminated without deleteriously affecting growth performance and carcass characteristics of late-finishing pigs.