Effect of phosphorus level and phytaseinclusion on the performance, bone mineralconcentration, apparent nutrient digestibility,and on mineral and nitrogen utilisationin finisher pigs

摘要

Two experiments were conducted to investigate the interaction between dietary Pconcentration and phytase (PHY) inclusion in the diet of finisher pigs. In Experiment1, the growth performance and bone analysis experiment, pigs (6 replicate groups of14 pigs each per treatment; initial body weight (BW) = 45.2 kg) were allocated to oneof six dietary treatments (for 74 days) in a 3 × 2 factorial arrangement: T1 – availableP in the diet = 1.5 g/kg; T2 = T1 with 500 units of phytase (FTU)/kg; T3 – availableP = 2.0 g/kg; T4 = T3 with 500 FTU/kg; T5 – available P = 2.5 g/kg; T6 = T5 with 500FTU/kg. Experiment 2 consisted of a digestibility and a P, Ca and N balance study, andpigs (6 per treatment; initial BW = 67.3 kg) were offered identical diets to those offeredin Experiment 1. There was an interaction between dietary P level and PHY inclusion foraverage daily gain (ADG) and carcass weight (CW; P < 0.05) in Experiment 1. Pigs offeredthe low P diet supplemented with PHY had a higher ADG and CW than pigs offered thenon-PHY, low P diet. However, there was no effect (P > 0.05) of PHY inclusion on ADG orCW with the medium or high P diets. Higher concentrations of ash, P and Ca in bone werenoted in pigs offered the medium and high P diets (P < 0.001) and PHY (P < 0.01) dietswhen compared to pigs offered the low P without PHY. Pigs offered diets supplementedwith PHY had lower faecal P output (P < 0.01) and a higher P digestibility (P < 0.001)and P retention (P < 0.05) than pigs offered diets without added PHY. In conclusion,supplementation of a low-P finisher diet with PHY resulted in pigs that had a similar carcassweight, but weaker bones than pigs offered a medium or high P diet.