Effect of phytase concentration in a low phosphorus weaner pig diet and its subsequent effect on bone development in the finished pig

Abstract

An experiment (complete randomised design) was conducted to investigate the linear and quadratic effects of an exogenous phytase inclusion level (0, 500, 1000 and 1500 FTU/kg) to a low phosphorus ( P) diet (4.2 g/kg) on weaner pig performance (7.8 kg in body weight, 12 replicates/treatment × 2 pigs/replicate = 96 pigs) and bone characteristics at both 30 kg and 100 kg body weight pigs. Bone samples were collected from 32 pigs (8/treatment) at the end of the weaner performance study (33 kg body weight). The remaining 64 pigs were then offered a commercial grower and finisher diet with 6 and 5.5 g total P/kg until slaughter at 100 kg. There was a linear improvement in overall feed conversion ratio (P < 0.01) as the level of phytase inclusion increased. There was a linear increase in bone ash (P < 0.01), calcium (Ca) (P < 0.01) and P (P < 0.05) concentration at 30 kg as the level of phytase inclusion increased. Offering weaner pig diets with increasing levels of phytase during the weaner stage (up to 33 kg body weight) resulted in the finished pig at slaughter having a quadratic increase in bone ash, Ca and P concentration (P < 0.001) with a maximum response in bone characteristics being reached at 1000 FTU/kg inclusion. In conclusion, increasing the phytase concentration of a low P diet improved feed efficiency and bone mineral concentration during the weaner stage (33 kg) which subsequently affected the bone mineral content at slaughter.