Níveis de metionina+cistina para frangos de corte de crescimento lento criados em diferentes sistemas de alojamento

Abstract

This research was carried out in the Institute of Zootecnia / Universidade Federal Rural do Rio de Janeiro, Seropédica, Brazil, with the objective of evaluating the levels of methionine+cystine in the slow-growing broiler chickens, raised in conventional pen and in free-range farming. The study consisted of 360 broilers at 28 days of age distributed in 15 boxes in the conventional pen and 15 free-range farming areas with Tifton 85 grass. The experimental line used was a completely randomized design in a factorial arrangement (5 X 2) with 5 levels of supplementation of DL-metionine (0.000; 0.1515; 0.3030; 0.4545; 0.6060%) and two kinds of raising pens. The basal diet of corn and soybean-meal had a 16.039% CP and 2.900Kcal/Kg ME with 0.56% of metionine+cystine total. Feed intake, weight gain, and feed efficiency were evaluated during the experimental periods 1, 2 and 3 (respectively 28 to 49, 28 to 70 and 28 to 85 days of age. At the end of each experimental period the birds were slaughtered simulating the ages of slaughter in the conventional, organic and free-range systems, respectively 49, 70, and 85 days of age. The following weights chilled carcass, cold carcass, breast, legs, heart, gizzard, abdominal fat, and carcass income. The results yielded the following ideal levels: 1.05% for feed efficiency and 0.93% based on weight gain in period 1; 0.85% for the highest weight of gizzards raised in conventional pen at 49 days of age; 0.89% for feed efficiency in period 2; 0.87% for the highest weight of abdominal fat in the broilers raised in free-range farming area slaughtered at 70 days of age; 0.89% was the lowest weight of broiler gizzards raised in free-range farming areas slaughtered at 85 days of age. The level of 0,71% of metionine+cystine was more economic in all periods. The permanence of broilers in good living conditions had an effect on the relation between feed ingestion and weight gain specially when slowgrowing broiler chickens slaughtered later.