Níveis de metionina + cistina e suplementação de vitamina B6 para suínos machos castrados e fêmeas dos 75 aos 100 kg

Abstract

Two experiments were conducted to evaluate the effect of the digestible methionine+cystine (Met+Cys) levels and B6 vitamin supplementation on performance, blood variable, carcass characteristics, meat quality and gene expression of enzymes involved in the methionine metabolism of barrows and gilts from 75 to 100 kg. In experiment I, fifty six barrows were used, averaging 75.11 ± 1.84 kg of initial weight, allotted in a completely randomized block design arranged in a 2×4 factorial scheme, composed by two supplementing B6 vitamin levels (1.58 e 3.58 mg/kg) and four digestible Met+Cys levels (0.350, 0.450, 0.550 and 0.650%), with seven replicates and one animal per experimental unit. In experiment II, fifty six female pigs were used, averaging 75.06 ± 1.68 kg of initial weight, distributed in identical design experiment I, except for digestible Met+Cys levels, what were of 0.370; 0.470; 0.570 and 0.670%. No interactions (P > 0.05) between B6 vitamin supplementation and digestible Met+Cys levels were observed (experiments I and II). The digestible Met+Cys levels did not affect pig performance. Was observed reduction (P < 0.01) in backfat thickness and increased (P = 0.01) in the yield of lean meat of barrows, as the increased digestible Met+Cys levels in diets. Supplementation of 3.58 mg vitamin B6/kg diet provided greater depth of Longissimus dorsi (P = 0.05) and better feed conversion (P = 0.05) (Experiment I). Plasma triglyceride concentrations presented a quadratic response (P < 0.01) as a function of digestible Met+Cys levels, wherein the lowest concentrations were estimated for the levels of 0.496 and 0.575% (experiments I and II, respectively). There was a linear increase (P = 0.01) in serum homocysteine levels due to the increase of Met+Cys levels in the diet of males, however, these levels were similar (P > 0.05) for females. Treatments did not affect the gene expression of the methionine synthase and cystathionine-γ-lyase enzymes in both sexes. Was observed a linear increase (P < 0.05) in loss of liquid by thawing and one quadratic response for the fluid loss by cooking and shear force as a function of digestible Met+Cys levels (experiments I and II). It is concluded that the requirements of digestible Met+Cys for barrows and gilts from 75 to 100 kg are lower than 10.46 g/day (0.350%) and 10.60 g/day (0.370%), respectively, based on performance variables and meat quality, and high levels of these amino acids reduce backfat thickness and increase the homocysteine blood concentration in barrows.