Effect of different digestible isoleucine/lysine ratios for broiler chickens

Fernando De Castro Tavernari,Horacio Santiago Rostagno,Paulo Roberto De Oliveira Carneiro,Guilherme Rodrigues Lelis,Jorge Armando Prada Luengas,Luiz Fernando Teixeira Albino,Richard Costa Polveiro,Rodolfo Alves Vieira

doi:10.1590/s1516-35982012000700020

Fernando De Castro Tavernari, Horacio Santiago Rostagno + Show 6 more

Open Access

https://doi.org/10.1590/s1516-35982012000700020

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Abstract

Two experiments were conducted to evaluate different digestible isoleucine/lysine ratios on diets for broiler chickens in the starter (7 to 21 days) and finishing (30 to 43 days) phases. For the tests, the experimental design was of randomized blocks with seven treatments (six different digestible isoleucine/lysine ratios and a control treatment) and eight repetitions of 25 and 20 birds (COBB males) per experimental unit in the starter and finishing phases, respectively. The diets met the requirements, except for isoleucine and lysine. To avoid excess lysine in the experimental diets, the digestible lysine content was calculated to be 87% and 89% of the recommended for the starter and finishing phases, respectively. The control treatment was adequate in lysine and isoleucine. Feed intake, weight gain, feed conversion and carcass yield in the two phases were evaluated. There was quadratic effect of different ratios on feed intake in the finishing phase and on weight gain and feed conversion rate in both phases. There was quadratic effect on breast meat yield and breast fillets in the starter phase, but there was no significant effect on carcass yield in the finishing phase. The digestible isoleucine/lysine ratio recommended for broilers in the starter phase (7 to 21 days) is 66% and for the finishing phase (30 to 43 days), it is 68%.

Highlights

The accurate knowledge of the nutritional requirements of essential amino acids and the nutritional composition of raw materials is essential for the correct balancing of diets and, in light of this, the constant update of the ideal protein profile is indispensable.In the ideal protein, lysine is viewed as a reference to the other essential amino acids, and several studies have been conducted with the first three limiting amino acids to broiler chickens
The experimental design was of randomized blocks with seven treatments and eight repetitions of 25 and 20 birds (COBB males) per experimental unit in the starter and finishing phases, respectively
The only criterion utilized for the determination of the requirement or the ratio between amino acids is weight gain, which can lead to an underestimate of requirements, once this parameter usually presents the lowest values, when compared with feed conversion, breast yield and abdominal fat (Leclercq, 1998b)

Summary

Introduction

Lysine is viewed as a reference to the other essential amino acids, and several studies have been conducted with the first three limiting amino acids to broiler chickens. Isoleucine is one of the limiting amino acids in diets with low protein for broiler chickens, and few studies have been conducted on the digestible isoleucine/ lysine ratio (Park & Austic, 2000). The only criterion utilized for the determination of the requirement or the ratio between amino acids is weight gain, which can lead to an underestimate of requirements, once this parameter usually presents the lowest values, when compared with feed conversion, breast yield and abdominal fat (Leclercq, 1998b).

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