Digestible lysine levels obtained by two methods of formulation of diets for 22-to-42-day-old broilers

Will Pereira De Oliveira,Juarez Lopes Donzele,Paulo Henrique Reis Furtado Campos,Silvana Marques Pastore,Marcus Vinícius De Lima Antunes,Rita Flávia Miranda De Oliveira Donzele,Luiz Fernando Teixeira Albino,Matheus Faria De Souza

doi:10.1590/s1516-35982014001100004

Will Pereira De Oliveira, Juarez Lopes Donzele + Show 6 more

Open Access

https://doi.org/10.1590/s1516-35982014001100004

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Abstract

The objective of this study was to evaluate the effect of digestible lysine levels in diets with or without supplementation of industrial amino acids on performance, carcass characteristics and nitrogen excretion in broilers of 22 to 42 days of age. Birds were distributed in a completely randomized experimental design in a 4 × 2 factorial arrangement, with four digestible lysine levels (9.0, 10.0, 11.0 and 12.0 g/kg) and two methods to obtain the lysine levels (variation in the proportion of corn and soybean meal, without supplementation; or supplementation of industrial amino acids), eight replicates and 20 birds per replicate. There was an interaction effect on the performance characteristics and on the weights and yields of prime cuts. In both diets, feed conversion improved linearly as the lysine levels were increased. Feed intake; weight gain; carcass, thigh and drumstick weights; and boneless breast yield increased and abdominal fat reduced linearly as the lysine levels were increased in the unsupplemented diet. The lysine levels of the supplemented diets linearly reduced the yield of drumstick and quadratically reduced the yields of bone-in and boneless breast up to the estimated levels of 10.4 and 10.7 g/kg, respectively. Diets without supplementation increased the excretion and retention of nitrogen. The levels of 9.0 and 12.0 g/kg digestible lysine obtained with supplementation of industrial amino acids and without it, respectively, provide the best performance and yield of prime cuts in the birds. Diets in which the digestible lysine levels are obtained without supplementation provide better performance responses and carcass characteristics compared with supplemented diets.

Highlights

Over the years, animal nutritionists have developed alterations in the quality of diets intended for broilers aiming to increasingly adapt these diets to meet the nutritional requirements of these birds
Several researchers have reported that birds fed diets with lower crude protein levels presented inferior performance to birds fed higher crude protein contents even when the ratios between the essential amino acids were kept constant (Assis et al, 2008; Oliveira et al, 2009), demonstrating that this method may not be suitable to determine the lysine requirement of broilers
The heat stress periods that the birds underwent might have influenced the voluntary feed intake and interfered with the weight gain rate and their prime cuts yield (Furlan, 2006)

Summary

Introduction

Animal nutritionists have developed alterations in the quality of diets intended for broilers aiming to increasingly adapt these diets to meet the nutritional requirements of these birds. Studies on the protein nutrition of broilers have considered the use of digestible amino acids in the formulation of diets, which makes it possible to reduce the amount of dietary protein and improve the adjustment between amino acids, contributing to decreasing the nitrogen excretion by the bird (Vasconcellos et al, 2011) To apply this practice, it is necessary to properly determine the requirements of amino acids by birds so that this supply of nutrients in the diet is adequate to ensure good performance rates. Reduction of the dietary crude protein and supplementation of industrial amino acids has been commonly practiced in most of the studies whose objective was to determine the lysine requirements of broilers (Martinez et al, 2002; Lana et al, 2005; Garcia et al, 2006) This technique enables greater flexibility in adjusting the amino acid levels of the diet. Several researchers have reported that birds fed diets with lower crude protein levels presented inferior performance to birds fed higher crude protein contents even when the ratios between the essential amino acids were kept constant (Assis et al, 2008; Oliveira et al, 2009), demonstrating that this method may not be suitable to determine the lysine requirement of broilers

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