Response of finisher broilers to reduced dietary calcium and phosphorus concentrations with phytase addition

It has been demonstrated that the phosphorus (P) requirements of modern broilers are significantly lower than historical industry practice (Li et al., 2017). However, it is also apparent from these studies that the P requirement is dependent on the dietary calcium (Ca) concentration and whether the diet is supplemented with phytase. Most of the contemporary research has been conducted in the starter phase, but this feeding trial has been conducted in the finisher phase (days 22- 49) to determine the influence of the addition of microbial phytase to diets containing different concentrations of ileal digestible phosphorus (IDP) and dietary Ca on growth performance in broilers fed a low IDP diet.

Eight hundred, day-old, Ross, male broiler chicks were fed a commercial diet to 21 days of age. Commencing on day 22, the experiment was a 2×4×2 factorial design with experimental diets based on wheat and sorghum; diets contained either 2.5 or 3.0 g/kg of IDP with 3.5, 4.5, 5.5 or 6.5 g/kg Ca. All the diets were prepared with or without phytase (Axtra PHY, 10000 TPT, 500 FTU/kg diet, Feedworks, Australia) supplementation. Each of the experimental diets was fed to 5 replicate pens with 10 birds per pen; grower diet, days 22 to 28; finisher diet, days 29 to 49. Body weight and feed intake were recorded weekly and FCR was calculated.

The result showed that birds fed the diet with phytase supplementation had higher (P < 0.05) body weight and feed intake than birds consuming the same IDP and Ca levels without phytase supplemented. Phytase also improved feed efficiency, as the FCR of phytase groups was significantly better (P < 0.05) than the non-phytase groups. Interestingly, IDP and Ca levels did not influence growth performance and feed efficiency among the treatments (P > 0.05); diets containing 2.5 g/kg IDP and 6.5 g/kg Ca with phytase supplemented showed the best numerical growth performance.

It can be concluded from this data that IDP values can be reduced in finisher diets. It also appears that the finisher broiler is less sensitive to the interrelationship between dietary Ca and P concentrations than the starter chick (Li et al., 2017).

ACKNOWLEDGEMENT: Research was funded by the RIRDC Chicken Meat Program.