Effect of dietary calcium level on growth performance, phosphorus digestibility and bone mineralization of lean-type growing-finishing pigs fed a low phosphorus diet supplemented with phytase

An experiment was conducted to determine the effect of dietary Ca level and phytase on growth, bone strength and digestibility of P and Ca in growing-finishing pigs. High lean-type pigs were randomly allocated to treatments on the basis of weight and gender. Average initial weight was 23.4kg and the experimental period was 11 days. Each treatment was replicated five times with five pigs per replicate. A corn-soybean meal diet was formulated to contain 0.60% Ca and 0.50% P in the growing period (23.4 to 62.5kg) and 0.50% Ca and 0.40% P in the finishing period (62.5 to 113.4kg). Dietary Ca was decreased by 0, 0.05 or 0.10 percentage units and phytase (Natuphos(TM)) was added at 300 or 250 units/kg in the growing and finishing periods, respectively, when P was decreased by 0.10 percentage units. Daily gain was increased (P<0.05) when 0.55% Ca and 0.40% P were fed with phytase in the growing period. There was no effect (P<0.10) on daily gain or feed intake in the finishing period. Overall, feed intake was higher (P<0.05) when dietary Ca decreased by 0.05 percentage units. Pigs fed the low P diet with phytase had lower fecal P levels (P<0.01), but similar apparent retention of P (P>0.10) compared to the control diet. Dietary Ca level did not affect (P>0.10) femur breaking strength or fecal P output. Dietary Ca can be reduced by 0.10 percentage units when phytase is fed at 300/250 units/kg and P is reduced from 0.50 to 0.40% and 0.40 to 0.30% in the diets of growing and finishing lean-type pigs, respectively.