The Effect of Dietary Supplementation with Phytase Transgenic Corn on Growth Performance,Phosphorus Utilization and Excretion in Growing Pigs (Sus scrofa)

Two experiments were conducted to investigate the effect of dietary supplementation with phytase transgenic corn (PTC) on growth performance,phosphorus (P) utilization and excretion in growing pigs.In Exp.1,180 pigs (Large White × Landrace,BW=37.7 kg) were randomly allotted to 4 treatments with 5 replicates of 9 pigs each in order to evaluate the effect of PTC supplementation in low-P diets on growth performance.Four corn soybean meal-based diets consisted of a positive control (PC) diet,a diet containing 500 units (U) of exogenous phytase kg-1 (EP) on the basis of low-P (inorganic P reduced by 0.05% from PC diet) and the low-P+500 (PTC1) or 750 (PTC2) phytase U of PTC kg-1.In Exp.2,20 barrows (Large White×Landrace,BW=31 kg,4 treatments with 5 replicates of 1 pig each) were randomly selected to evaluate the effect of PTC in low-P diets on serum parameters and nutrient utilization.Diets in Exp.2 were similar to those in Exp.1 except that the EP group was replaced by a low-P diet without exogenous phytase supplementation as a negative control (NC) group.The results from Exp.1 showed that the average daily gain (ADG) in the PTC2 group was significantly higher (P<0.05) than that in the EP group over all periods.On the other hand,the feed:gain (F:G) ratio of the EP group was significantly higher (P<0.05) than that of the PTC2 group during 1-21 and 1-42 d,respectively.There were no differences in average daily feed intake (ADFI) among all treatments (P>0.05).The results from Exp.2 showed that the concentration of serum Ca in the NC group was the highest (P<0.05),while the concentration of serum P in the PTC2 group was the highest (P<0.05) among all treatments.There was a significant decrease (P<0.05) in the P apparent digestibility of the NC group compared with the other groups,and that of PTC2 group was the best.Furthermore,fecal P excretion was reduced (P<0.05) from 1.80 g d-1 in the PC group to 1.28 g d-1 in the PTC2 group.In conclusion,dietary supplementation with PTC could reduce the application of inorganic P,decrease fecal P excretion,and improve the growth performance of growing pigs.