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.

Reham Abou-Elkhair,Sara Ketkat,Hamada Ahmed,Shaimaa Selim

doi:10.14202/vetworld.2020.1234-1244

Reham Abou-Elkhair, Sara Ketkat + Show 2 more

Open Access

https://doi.org/10.14202/vetworld.2020.1234-1244

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Abstract

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<0.05; linear, p<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<0.001; linear, p<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<0.05; linear, p<0.05) serum triglycerides, glutamate oxaloacetate transaminase, glutamate pyruvate transaminase, and alkaline phosphatase, while increased (p<0.01; linear, p<0.01) phagocytic activity and phagocytic index. The mRNA expression of splenic and cecal tonsil interleukin 4 and interferon gamma was upregulated (p<0.001; linear, p<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<0.01; linear, p<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.

Highlights

Over the past few decades, one of the most important roles of nutritionists in the poultry industry is to reduce the feed cost while ensuring maximum efficiency of utilization and growth performance
The mRNA expression of splenic and cecal tonsil interleukin 4 and interferon gamma was upregulated (p
The effects of supplementing combined synthetic AA profile in a low-protein diet for broiler chickens during the experimental periods on body weight (BW), BW gain (BWG), feed intake (FI), and feed conversion ratio (FCR) are presented in Table-5

Summary

Introduction

Over the past few decades, one of the most important roles of nutritionists in the poultry industry is to reduce the feed cost while ensuring maximum efficiency of utilization and growth performance. Elevated ammonia concentrations in broiler houses have been reported to decrease growth performance, reduce immunity responsiveness, and respiratory problems in poultry [1,2]. The Creative Commons Public Domain Dedication waiver (http:// creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated

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