Relação aminoácidos sulfurados e lisina digestível em rações para frangos de corte

Abstract

The present study aimed to evaluate sulfur aminoacids: digestible lysine (SAAsdig.:Lysdig.) ratio on performance, carcass and cut yields, myopathy evaluation, skin and feather quality, blood parameters, and gene expression in broilers. A total of 1440 one-day-old male broiler chicks, Ross 308, were distributed in two trials, in a completely randomized design, containing 4 treatments, 9 replications and 20 birds per experimental unit (EU) in each trial. The experimental treatments were based on the relationship between sulfur aminoacids (SAAs)dig.:Lysdig. in an increasing manner: T1= 78, 80, 82 and 84%; T2= 76, 78, 80 and 82%; T3=74, 76, 78 and 80%; and T4=72, 74, 76 and 78% and decreasing: T1= 84, 82, 80 and 78%; T2= 82, 80, 78 and 76%; T3=80, 78, 76 and 74%; and T4=78, 76, 74 and 72%, for the phases of 1 to 10 days, 11 to 24 days, 25 to 35 days and 36 to 44 days, respectively. The data were subjected to normality and homogeneity tests, followed by analysis of variance. When significant, data were evaluated by polynomial regression. In treatments with increasing and decreasing ratios, a linear effect was found for sulfur-containing amino acid consumption (SCAAC) in all phases, showing a positive correlation between the SCAA:Lysdig ratio and SCAA consumption. Birds in the decreasing ratio treatment showed a quadratic effect for feed intake (FI) in the pre-starter phase and a linear effect for feed conversion ratio (FCR), where the highest ratio showed better FCR, except from 1 to 10 days. The diameter of the primary follicle (DPF) of the feather at 28 days, in the decreasing relationship and at 44 days in the increasing relationship, showed a linear effect. For birds in the decreasing relationship, a quadratic adjustment was observed for DPF and epidermis thickness (ET) at 44 days. For skin elasticity and resistance at 28 days, the breaking tension (BT) showed a quadratic effect in the increasing ratio trial and a linear effect at 44 days. In the decreasing ratio trial, a linear effect was observed for shear force and elasticity, with a quadratic adjustment for BT at 44 days. The parameters of the eighth feather at 28 days showed a linear effect for length of blade 1 (Blade1Len) in the increasing trial. In birds from the decreasing trial at 28 days, feather yield (FeathYield) showed a linear effect, the weight of the eighth feather (FeathWt) and the thickness of the calamus (CalThick) adjusted quadratically, and at 44 days, a quadratic effect was observed for Blade1Len, Blade2Len, and Blade3Len of the eighth feather. It was concluded that performance, skin elasticity and resistance, and feathering parameters were more influenced by decreasing SAA:lysine ratios.