Final report summary: Branched-chain amino acids in wheat-based, crude protein-reduced diets

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The successful development of a reduced-protein broiler diet is an ongoing focus for the Australian chicken meat industry. Reduced-CP diets have the potential to halve the industry’s dependence on imported soybean meal, and thus reduce its exposure to fluctuations in global soybean meal prices. Such diets can also reduce the carbon footprint of feed production, improve litter quality, reduce nitrogen pollution and ammonia emissions, and enhance bird welfare.

However, several tangible obstacles are thwarting the development of reduced-CP diets. Broiler diets are formulated to meet ideal (digestible) amino acid ratios (IAAR), but the likelihood is that the IAAR for a reduced-CP diet is not identical to that for a standard diet. Thus, because of their nutritional importance, there is a need to accurately identify the branched-chain amino acid (BCAA) requirements for broiler chickens offered reduced-CP diets.

This project evaluated elevated inclusions of BCAAs in wheat- and sorghum-based diets, and L-carnitine inclusions in sorghum-based diets with three tiers of crude protein (CP) concentrations. Elevated BCAA inclusions in wheat-based diets did not influence growth performance in feeding study BCAA 01. However, elevated BCAA inclusions significantly enhanced growth performance in broilers offered sorghum-based diets in BCAA 02, but depressed growth performance when included in wheat-based diets. In BCAA 03, L-carnitine inclusions significantly improved weight gain and feed conversion ratio (FCR) in broilers offered 160 g/kg CP sorghum-based diets, but did not influence the performance of broilers offered 190 and 220 g/kg CP diets.

The selection of a feed grain for a reduced-CP diet is pivotal because starch digestion rates, protein contents and amino acid profiles assume importance. Consideration is given to the likelihood that non-bound amino acids are more prone to be deaminated, resulting in excessive ammonia levels, which require detoxification.

Published journal articles: Greenhalgh, S., Macelline, S. P., Chrystal, P. V., Liu, S. Y., Selle, P. H. (2022). An evaluation of elevated branched-chain amino acid inclusions on the performance of broiler chickens offered reduced-crude protein, wheat-based diets from 7 to 28 days post-hatch. Animal Feed Science and Technology, 286, 115255. https://doi.org/10.1016/j.anifeedsci.2022.115255.

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