Redução do teor de proteína bruta em dietas suplementadas ou não com L-glicina para frangos de corte

Abstract

Four experiments were carried out in a completely randomized experimental design to evaluate the nutrient utilization and determination of net energy, the body composition and carcass characteristics of male broiler chickens fed low crude protein (CP) diets. These diets were suplemented with essential amino acids or essential and glycine or different total Gly+Ser levels. During the initial phase, there was a decreasing linear effect of CP levels on feed:weight gain ratio, weigth gain, final body weight and feed intake. Protein reduction increased linearly carcass fat and carcass dry matter. During the growing phase there was a quadratic effect of CP levels on weight gain, final body weight and feed intake which were maximized on 19,28; 19,35 and 16,75% CP levels respectively. The carcass fat increased linealy. There was a quadratic effect of CP level on breast yield; with estimated maximum performance for broilers fed 18,28% CP diet. The effects of CP levels with L-Glycine suplementation were similar to those obtained without supplementation. There was a linear effect of CP levels on dry matter and crude energy digestibility. The best CP digestibility was estimated for 15.33% CP diet. The best nitrogen retention was estimated for 18,28% CP diet. There was no effect of CP levels on diets net energy. The different levels of Gly+Ser. in a low CP diet improved linearly all performance parameters. The low crude protein increased carcass fat in the initial phase.