SID Methionine+Cystine Levels and Vitamin B6 Supplementation on Performance, Blood Parameters and Metabolic Enzymes Gene Expression of Finishing Barrows

This study aimed to evaluate the effects of dietary SID methionine+cystine (Met+Cys) levels and vitamin B₆ (B6) supplementation on performance, blood parameters and enzymes expression of finishing barrows. Fifty-six crossbred barrows (Talent x Topigs 20) averaging 75.11 ± 1.84 kg of body weight (BW) were distributed in a completely randomised block design arranged in a 2×4 factorial scheme consisting of two B₆ supplementation levels (1.58 and 3.58 mg/kg) and four SID Met+Cys levels (0.35, 0.45, 0.55 and 0.65%), with seven replicates and one animal per experimental unit. Average daily gain, average daily feed intake, feed/gain (F/G), plasma concentrations of glucose, urea, total proteins, creatinine and triacylglycerol, serum homocysteine levels and gene expression of methionine synthase (MS) and cystathionine γ-lyase (CGL) were evaluated. The F-test was used on the B₆ supplementation data. The degrees of freedom related to SID Met+Cys levels were used in orthogonal polynomials to obtain the regression equations. No interactions (P > 0.05) between B₆ supplementation and SID Met+Cys levels were observed. The highest B₆ supplementation (3.58 mg/kg) decreased (P = 0.05) the F/G and high (P = 0.05) plasma glucose concentration. Triglycerides showed a quadratic response (P = 0.01), wherein the lowest concentration (29.42 mg/dL) was estimated at 0.496% SID Met + Cys. Although treatments did not affect the expression of MS or CGL, there was a linear increase (P=0.01) in serum homocysteine levels due to increasing SID Met+Cys in the diet. SID Met+Cys requirement for barrows (75–100 kg BW) was 10.46 g/day and high levels of these amino acids increased the homocysteine blood concentration. Dietary supplemention of 3.58 mg B₆/kg improved the F/G ratio but was not efficient to improve homocysteine metabolization by the trans-sulphuration pathway.