Supplementation of a low-protein diet with tryptophan, threonine, and valine and its impact on growth performance, blood biochemical constituents, immune parameters, and carcass traits in broiler chickens

Abstract

<jats:p>Aim: This study aimed to investigate the effects of protein reduction with supplementation of limiting amino acids (AA, tryptophan, threonine, and valine) on growth performance, blood biochemical, immunity parameters, and carcass traits in broiler chickens. Materials and Methods: Three hundred one-day-old broiler chicks were randomly allotted into three treatment groups, with five replicates per treatment and 20 broiler chickens per replicate. The three experimental diets were formulated with different dietary crude protein (CP) %, (control [CON] and CON with 1% [CP-1%] or 2% [CP-2%] less CP units) during the starter, grower, and finisher phases. The CP of the experimental diets were 22, 21, and 20% for the starting period (day 1-14); 20, 19, and 18% CP for the growing period (day 15-28); and 18, 17, and 16% CP for the finishing period (day 29-35) in CON, CP-1%, and CP-2%, respectively. The low-CP diets (CP-1% and CP-2%) were supplemented with combined AA, threonine+tryptophan+valine, to meet the respective levels of the CON diet. Results: The CP-2% group had greater (p&lt;0.05; linear, p&lt;0.05) final body weight and gain and better feed conversion ratio. The combined AA inclusion in the low-CP diet (CP-1% and CP-2%) increased (p&lt;0.001; linear, p&lt;0.001) carcass and breast meat yield as well as CP% of breast meat. The reduction of CP% with AA supplementation (CP-2%) decreased (p&lt;0.05; linear, p&lt;0.05) serum triglycerides, glutamate oxaloacetate transaminase, glutamate pyruvate transaminase, and alkaline phosphatase, while increased (p&lt;0.01; linear, p&lt;0.01) phagocytic activity and phagocytic index. The mRNA expression of splenic and cecal tonsil interleukin 4 and interferon gamma was upregulated (p&lt;0.001; linear, p&lt;0.001) in the low-CP diets supplemented with AA (CP-1% and CP-2%). Dietary supplementation with AA to low-protein diets improved (p&lt;0.01; linear, p&lt;0.01) the economic returns of broiler chickens. Conclusion: A reduction of dietary CP and increased synthetic AA such as threonine, valine, and tryptophan should be considered to improve performance, health, and immunity in broiler chickens.</jats:p>

Effect of dietary serine supplementation on performance, egg quality, serum indices, and ileal mucosal immunity in laying hens fed a low crude protein diet

“…It has been reported that prolonged duration of a LCP diet will decrease plasma AA concentration and is associated with high level of infections in laying hens ( Fafournoux et al., 2000 ). In concert with a previous study ( Abou-Elkhair et al., 2020 ), this study showed that dietary CP reduction induced intestinal inflammation in laying hens, evidenced by the elevated mRNA expression of ileal proinflammatory cytokines inclusive of IFN-γ and IL-1β. They increased by 228.04% and 82.27%, respectively.…”

“…Low crude protein ( LCP ) diets have been identified to potentially provide economic, environmental, healthy, and welfare benefits to poultry ( Abou-Elkhair et al., 2020 ). Supplemental crystalline amino acids ( AA ) in LCP diets are supposed to be an effective strategy for reducing feed costs, nitrogen excretion, and increasing feed utilization ( Ospina-Rojas et al., 2012 ; Hilliar et al., 2019 ).…”

Supplemental magnolol or honokiol attenuates adverse effects in broilers infected with Salmonella pullorum by modulating mucosal gene expression and the gut microbiota

“…The predicted functions of the ileum microbiota showed that pathways related to valine, aspartate, glutamate, and C5-branched dibasic acid metabolism were decreased in broilers challenged with S. pullorum , while magnolol could increase these pathways. Leucine, valine, and isoleucine, which are representative of branched-chain amino acids, have key physiological roles in the regulation of immunity [ 46 ] and fat metabolism [ 47 ]. Several studies have shown that C5-branched dibasic acid metabolism is related to energy generation and is enriched in healthy animals [ 48 , 49 ].…”

Performance and immune response of broilers born to breeders of different ages and fed different valine levels

“…Diets containing 10.3 and 11.3 g/kg of valine, corresponding to a valine:lysine ratio of 0.84:1 and 0.92:1, respectively, in the nutritional composition, led to a reduction in FI. Abou-Elkhair et al (2020) found that amino acid supplementation resulted in low daily FI and concluded that this finding suggested that any excess amino acids may be deaminated, producing more energy. As a consequence, FI would decrease as an animal defense mechanism to limit the absorption and catabolism of excess amino acids.…”

“…Dietary BCAA deficiency impairs the innate immune function, due to the shortage of lymphocytes and white blood cells, and increases susceptibility to pathogens. Branched-chain amino acids are related to better humoral and cellular immune response in broiler chickens (Abou-Elkhair et al, 2020).…”