Abstract
This study was conducted to evaluate the effects of digestible lysine levels in diets with and without supplementation of industrial amino acids on performance and fat deposition in the carcass of broilers in the starter phase. One thousand four hundred and forty chickens with initial weight of 168.1±5.0 g were distributed in a completely randomized experimental design, in a 5 × 2 factorial arrangement, composed of five digestible lysine levels (10.0, 11.0, 12.0, 13.0 and 14.0 g/kg) and two types of diet (diet with different proportions of corn and soybean meal and diet supplemented with industrial amino acids to obtain the digestible lysine levels), with eight replications and 18 birds per replication. There was interaction effect only on weight gain and fat deposition in the birds. The lysine levels reduced feed intake linearly in both diets, but caused a linear increase in lysine intake. The lysine levels quadratically affected weight gain and feed conversion, which improved up to the estimated levels of 13.0 and 12.8 g/kg lysine, respectively, when the corn:soybean meal ratio of the diet changed. In the diets supplemented with amino acids, the lysine levels increased weight gain and improved feed conversion linearly. Regardless of the type of diet, protein deposition increased linearly, whereas fat deposition reduced also linearly, as the lysine levels in the diets were increased. The levels of 13.0 and 14.0 g/kg digestible lysine provide, respectively, the best performance in birds fed a diet in which the proportion of corn and soybean meal varies and a diet supplemented with industrial amino acids, in the period from 8 to 21 days of age.
Highlights
IntroductionBroilers have genetic potential for rapid growth and elevated meat deposition in the carcass, and to ensure satisfactory production rates, research has been conducted aiming at the development of increasingly more appropriate diets to meet the nutritional requirements of these birds
Broilers have genetic potential for rapid growth and elevated meat deposition in the carcass, and to ensure satisfactory production rates, research has been conducted aiming at the development of increasingly more appropriate diets to meet the nutritional requirements of these birds.The dietary protein is considered the main nutrient to be converted and deposited as muscle tissue in the carcass (Suida, 2001)
It allows for reducing the amino-acid load of diets, enabling more accurate adjustments of their levels (Oliveira Neto & Oliveira, 2009), the effects of this practice on bird performance have presented controversial results, demonstrating that the knowledge of the reduction of crude protein from diets supplemented with essential amino acid does not change performance or carcass characteristics of broilers; on the other hand, impaired performance and carcass quality and low yield in the cuts of broilers fed diets formulated by this method have been reported by several researchers (Aletor et al, 2000; Aftab et al, 2006; Assis et al, 2008; Namroud et al, 2008)
Summary
Broilers have genetic potential for rapid growth and elevated meat deposition in the carcass, and to ensure satisfactory production rates, research has been conducted aiming at the development of increasingly more appropriate diets to meet the nutritional requirements of these birds. The method utilized to determine the lysine requirement employs the reduction of dietary crude protein and its supplementation with essential amino acids so that they are not below the bird requirements (Rostagno et al, 1999). It allows for reducing the amino-acid load of diets, enabling more accurate adjustments of their levels (Oliveira Neto & Oliveira, 2009), the effects of this practice on bird performance have presented controversial results, demonstrating that the knowledge of the reduction of crude protein from diets supplemented with essential amino acid does not change performance or carcass characteristics of broilers; on the other hand, impaired performance and carcass quality and low yield in the cuts of broilers fed diets formulated by this method have been reported by several researchers (Aletor et al, 2000; Aftab et al, 2006; Assis et al, 2008; Namroud et al, 2008). This study was conducted to determine the digestible lysine requirement for broilers from 8 to 21 days of age utilizing two diet-formulation methodologies: alteration of the proportion of corn and soybean meal, and supplementation of diets with industrial amino acids
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