Phytase Supplementation of Wheat-Based Broiler Diets Reduces Dependence on Meat-and-Bone Meal

Abstract

It is permissible to include meat-and-bone meal (MBM) in broiler diets in many countries outside the European Union, including Australia, where MBM is usually advantaged by being a relatively inexpensive source of phosphorus and protein. However, some producers may prefer to reduce their dependence on MBM as this feed ingredient has several disadvantages and may be a barrier to exports of chicken-meat. Therefore, the purpose of this experiment was to investigate the extent to which phytase supplementation can reduce MBM inclusion levels in wheat-based broiler diets. Standard and modified starter, grower and finisher diets were formulated so that modified diets contained lower MBM inclusions and reduced nutrient specifications. The standard and modified diets, the latter supplemented with 0, 500 or 750FTU/kg phytase (Phyzyme® XP), were offered to a total of 840 broilers in 24 floor pens from 1-42 days of age and the effects of dietary treatments on growth performance were determined. For the grower phase (15-28 days), five broilers from each floor pen were transferred to cages to permit total excreta collection to determine apparent metabolisable energy (AME) and nitrogen (N) retention. Acid insoluble ash was included in the caged birds’ diets and ileal digesta collected at 28 days to determine the effect of dietary treatments on apparent ileal digestibility (AID) of amino acids. Lowering nutrient specifications reduced growth performance and increased mortality rates over 42 days but this decline in performance was overcome by the addition of 750FTU/kg phytase to modified diets. Feed ingredient costs per unit of live weight gain were also reduced by phytase addition. Reducing dietary levels of MBM increased amino acid digestibilities in the modified grower diet. Moreover, phytase supplementation of modified diets linearly increased AID coefficients of alanine, aspartic acid, glycine, isoleucine, leucine, serine, threonine and tyrosine to a significant extent. Also, phytase (750FTU/kg) supplementation of the modified diet significantly increased AME by 0.27MJ/kg on a dry matter (DM) basis. Overall consumption of MBM was reduced from 233g to 14g per bird from 1-42 days of age following dietary modifications. It is noteworthy that reduced inclusions of MBM, coupled with phytase supplementation, enhanced ileal digestibility of total amino acids by 5.3% (0.834 versus 0.792). This study demonstrates that it is feasible to reduce MBM contents and nutrient specifications in wheat-based broiler diets in association with phytase supplementation without the addition of inorganic phosphorus sources.