Abstract
Simple SummaryThe conversion of dietary protein and amino acids into chicken-meat is a dynamic and complex process. Dietary protein is transferred to protein in a chicken carcass at a conversion ratio in the order of 2.50:1, which leaves scope for improvement. Nevertheless, this conversion ratio in broiler chickens cannot be matched by other terrestrial food-producing animals. The quest for sustainable chicken-meat production would be greatly facilitated by enhancing the efficiency of this conversion. Therefore, this review explores the various pathways and processes involved with the objective of identifying approaches and strategies whereby the transition from dietary protein to chicken-meat protein can be advanced.This review considers the conversion of dietary protein and amino acids into chicken-meat protein and seeks to identify strategies whereby this transition may be enhanced. Viable alternatives to soybean meal would be advantageous but the increasing availability of non-bound amino acids is providing the opportunity to develop reduced-crude protein (CP) diets, to promote the sustainability of the chicken-meat industry and is the focus of this review. Digestion of protein and intestinal uptakes of amino acids is critical to broiler growth performance. However, the transition of amino acids across enterocytes of the gut mucosa is complicated by their entry into either anabolic or catabolic pathways, which reduces their post-enteral availability. Both amino acids and glucose are catabolised in enterocytes to meet the energy needs of the gut. Therefore, starch and protein digestive dynamics and the possible manipulation of this ‘catabolic ratio’ assume importance. Finally, net deposition of protein in skeletal muscle is governed by the synchronised availability of amino acids and glucose at sites of protein deposition. There is a real need for more fundamental and applied research targeting areas where our knowledge is lacking relative to other animal species to enhance the conversion of dietary protein and amino acids into chicken-meat protein.
Highlights
It was concluded that more glucose was used as an oxidative substrate by the gut mucosa following the feeding of slowly digestible pea starch, thereby permitting more amino acids to enter the portal circulation as they were spared from catabolism in the gut mucosa
These quadratic relationships indicate that there is an ideal balance between intestinal uptakes of protein as oligopeptides and monomeric amino acids and energy as glucose from starch to generate optimal growth performance
Vagaries in apparent amino acid digestibility coefficients and disappearance rates pursuant to reductions in dietary crude protein (CP) are in evidence, which complicate the formufor sustainable chicken-meat production and this opportunity has been central to this review
Summary
Non-bound, amino acids were considered as alternatives to soybean meal, as reviewed by Selle et al [12] These researchers contended that the chicken-meat industry’s dependence on soybean meal would be halved if CP reductions of 50 g/kg are realised without compromised broiler growth performance. This would involve judicious dietary inclusions of non-bound amino acids to meet requirements. The objective of this review is to explore the transition of dietary protein and amino acids into carcass protein in broiler chickens and to identify strategies that may enhance this conversion That this is discussed in relation to other animal species, including pigs, rats and humans, is indicative of the lack of data specific to avian species in some key areas
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