Effects of phytase and 25-hydroxyvitamin D₃ inclusions on the performance, mineral balance and bone parameters of grower-finisher pigs fed low-phosphorus diets.

摘要

Two experiments, a performance experiment and a mineral balance study, were conducted on grower-finisher pigs (42 to 101 kg live weight) to investigate the effects of Peniophora lycii phytase enzyme and 25-hydroxyvitamin D₃ (25-OHD₃) on growth performance, carcass characteristics, nutrient retention and excretion, and bone and blood parameters. The two experiments were designed as a 2x2 factorial (two levels of phytase and two levels of 25-OHD₃). The four diets were T1, low-phosphorous diet; T2, T1+phytase; T3, T1+25-OHD₃ and T4, T1+phytase+25-OHD₃ diet. In all, 25 micro g of 25-OHD₃ was used to replace 1000 IU of vitamin D₃ in diets T3 and T4. Diets were pelleted (70 degrees C) and formulated to contain similar concentrations of energy (13.8 MJ DE/kg), lysine (9.5 g/kg) and digestible phosphorus (P; 1.8 g/kg). Neither the inclusion of phytase nor 25-OHD₃ in the diet had any effect on pig performance. There was an interaction between phytase and 25-OHD₃ on calcium (Ca) and P retention (P<0.01) and on the apparent digestibility of ash (P<0.01), P (P<0.001) and Ca (P<0.001). Pigs offered phytase diets only, had a higher retention of Ca and P and digestibility of ash (P<0.01), P (P<0.001) and Ca (P<0.01) compared with pigs offered unsupplemented diets. However, when the combination of phytase and 25-OHD₃ were offered, no effects were detected compared with 25-OHD₃ diets only. Pigs fed phytase diets had higher bone ash (P<0.01), bone P (P<0.01) and bone Ca (P<0.05) concentrations compared with pigs offered non-phytase diets. In conclusion, pigs offered phytase diets had a significantly increased bone ash, Ca and P than pigs offered unsupplemented phytase diets. However, there was no advantage to offering a combination of phytase and 25-OHD₃ on either bone strength or mineral status compared to offering these feed additives separately.