Effects of phosphorus level and microbial phytase supplementation on the performance and bone mineralization in pigs

An experiment was conducted with 192 growing and finishing pigs in order to evaluate the phosphorus (P) requirement of the pigs and the efficacy of Aspergillus niger phytase on a barley based diet, and to study phase feeding of P and phytase. The performance of the pigs and certain chemical and physical parameters of their tibia and fibula bones were used as criteria for the effectiveness of the treatments. The variables in diet formulation were microbial phytase addition of 500 FTU kg(-1) (-/+) and three P levels-high (HP), medium (MP) and low (7.7, 6.1 and 4.5 g of total P kg(-1) dry matter, respectively). Two additional diets were combinations of the former: MP - LP - and MP + LP -. The medium P level was sufficient for the pigs from 30 kg up to slaughter at 100 kg with the growth level of 900 g day and feed conversion ratio (FCR) of 2.60, but the lowest P level led to an impaired average daily gain (ADG) and FCR. Microbial phytase improved the ADG (P < 0.05) and FCR of pigs (P < 0.05) on LP diet. No signs of leg weakness were observed in the pigs on any of the diets. The tibia densities decreased with decreasing dietary P. The ash content of fibula bones increased and their P content decreased with declining dietary P. Lowering the P content of the diet, using an appropriate phase feeding of P, and adding phytase into the diet could support the normal growth rate of the pigs and reduce the amount of P excretion in faeces.