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 *, /** or 1/* FTU/kg phytase (Phyzyme ῍ XP), were o#ered to a total of 2.* broilers in ,. floor pens from +ῌ., days of age and the e#ects of dietary treatments on growth performance were determined. For the grower phase (+/ῌ,2 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 ,2 days to determine the e#ect of dietary treatments on apparent ileal digestibility (AID) of amino acids. Lowering nutrient specifications reduced growth performance and increased mortality rates over ., days but this decline in performance was overcome by the addition of 1/* FTU/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 coe$cients of alanine, aspartic acid, glycine, isoleucine, leucine, serine, threonine and tyrosine to a significant extent. Also, phytase (1/* FTU/kg) supplementation of the modified diet significantly increased AME by *.,1 MJ/kg on a dry matter (DM) basis. Overall consumption of MBM was reduced from ,--g to +. g per bird from +ῌ., 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 /.-ῌ (*.2-. versus *.13,). 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.
Background: Betaine has the potential to spare methionine and choline as methyl-group donors, and is thought to improve broiler performance under conditions of stress. An experiment was conducted to ascertain the effects of supplemental betaine on performances and physiological responses of broilers exposed continuously to thermal stress. Materials and methods: Male broilers (n=128, divided into four groups, with eight replicate cages in a group) received diets containing suboptimal levels of methionine and metabolizable energy and supplemented with 1.3 g/kg and 2 g/kg betaine hydrochloride from day 1 to 38. The positive control (PC) did not contain supplemental betaine, and the negative control (NC), to which betaine was added, was deficient in methionine and energy and devoid of added choline. The experiment included assessment of growth, feed-conversion ratio, rectal temperature and respiration rates, and assay of blood hormones and metabolites. Results: Betaine at both the levels of inclusion improved live weight and feed intake over the PC and the NC groups. Rectal temperature and respiration rates were also lower in the betainesupplemented groups, indicating a sequestering effect of betaine on metabolic rates of thermally stressed broilers. Carcass yield was unaffected. Betaine-supplemented groups had better thyroid activity than the NC and PC groups of birds. Conclusion: Based on this study, it was inferred that in tropical countries betaine may be effectively used to ameliorate the negative impact of high ambient temperature in broiler chickens. The findings also suggest that at an appropriate dose, betaine may spare some quantity of dlmethionine and dietary energy to support the growth process of heat-stressed broilers. However, further studies are warranted to assign a definite methionine and energy matrix to supplemental betaine that can be used in broiler diets without inviting any risk of drop in production.
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