Avaliação de fontes de metionina sintética desempenho e expressão de genes do metabolismo aminoácidos sulfurosos no tecido hepático de frangos

Abstract

This study was designed to evaluate the requirement and effect of digestible Methionine + Cystine (Met+CysD) levels and the commercial methionine sources on zootechnical performance, cuts yield and gene expression regulation which encoding the enzymes of sulfur amino acid metabolism. Therefore, in Chapter I two experiments are described. In the first one, it was aimed to determine the requirement of Met+CysD, using DL Methionine and 5 levels of Met+CysD (0.63; 0.76; 0.88; 1.00 and 1.13%) with 6 repetitions and 15 chickens per repetition, totaling 450 chickens (Cobb 500 slow feathering®) over a period of 8-21 days. According to the obtained results, the Met+CysD requirement was estimated at 1.016 and 0.953% for weight gain and feed conversion, respectively. In the second experiment, the effect of three DL-Met substitutions by DL HMTBA, and three Met+CysD levels (0.63, 0.88 and 1.13 at 8-21 days; 0.58, 0.83 and 1.08 from 8-33 days and 0.52, 0.77 and 1.02% from 8-42 days) on deficiency, requirement and excess; in addition to a diet with L-Methionine (positive control) at the level that attend the requirement on performance, carcass yield and noble cuts, jejunum histomorphometry and feather data. In the 8-21 days phase between levels, Met+CysD deficiency promoted increased dietary feed intake when was used 50%DL-Met:50%DL HMTBA. To the next phase, between 8-33 days, it was observed which the deficient diet provided an increase in feed intake in relation to the other levels. Then, from 8-42 days the requirement on Met+CysD promoted reduction of feed intake of chickens when 100% DL-Met and 100% DL-HMTBA was provided. Regarding weight gain in the 8-21 days phase, Met+CysD deficiency caused a decrease it during period; while the diet with L Met provided greater weight gain. The broilers in the 8-33 days phase which received the Met+CysD excess diet and with 100%DL-HMTBA presented higher weight gain. The Met+CysD deficient level provided lower weight gain when 100%DL-HMTBA was used in first phase (8-42 day), as well as, the broilers which consumed the 50%DL Met:50%DL-HMTBA diet at this level had the highest weight gain. Substitution of 100% DL-Met in excess level promoted greater weight gain. Met+CysD deficient diet both at 8-21 and 8-33 days phases worsened the feed conversion. At 42 days, it was found which in the deficient level there were no differences between used substitutions. The best feed conversion was observed in broilers that was feed by diet with attended the Met+CysD requirement with 100%DL-Met source. For the excess level, the better feed conversion was obtained with 100%DL-Met was provided to animals. Similarly, to performance, the Met+CysD deficiency impaired live weight, absolute and relative carcass weights and noble cuts. Regarding the substitutions, the broilers which consumed the 100%DL-Met diet presented higher live weight and absolute and relative weights of breast and boneless breast. The L-Met source provided higher both absolute and relative breast and boneless breast weights. The 100% DL-HMTBA source induced a higher percentage of feathers and greater weight of the eighth primary feather at 21 days. The positive control diet was efficient in the feathering with higher feather percentages. For the jejunum morphometry during phase 8-21 days, Met+CysD deficiency with 100%DL-HMTBA substitution provided higher villus height than the others. At the Met+CysD level in the requirement, it was observed a smaller crypt depth to 100%DL-Met. Lower villus: crypt ratio was observed in the broiler jejunum which receiving 100%DL-Met at Met+CysD deficient level. In phase 8-33 days, Met+CysD deficiency with 100% DL-Met replacement provided higher villus height than the others. At the level that attend the requirement, it was observed higher villus height using diet with 100%DL-Met. Already for diet with Met+CysD in the requirement provided greater crypt depth with 100%DL-HMTBA. The greater crypt depth was observed at the deficient Met+CysD level in all studied substitutions. In the diet which attend the requirement, the villus: crypt ratio was higher when compared to the others. To all analyzed days (8-42 days phase), Met+CysD deficiency provided higher villus height and crypt depth for all three substitutions. Met+CysD requirement was estimated at 0.953% and 1.016% for feed conversion and weight gain, respectively. Met+CysD excess level and sources (100% DL-Met and L methionine) were efficient for performance, intestinal morphometry and commercial cuts characteristics; broilers which was fed with DL-HMTBA level in excess and L Methionine presented higher feather percentages. In Chapter II, a completely randomized design in a 3x2 factorial arrangement was used, consisting of 3 Met+CysD levels (deficient, demanding and excess) and 2 sources (DL-Met and DL-HMTBA), totaling 6 treatments with 6 repetitions and fifteen broiler chickens each, to evaluate their implications on the performance and expression of genes encoding sulfur amino acid metabolism enzymes. The deficient Met+CysD level compromised feed conversion, while the excess level provided better feed conversion; regarding sources, DL-Met was more efficient than DL-HMTBA. Deficient and excess Met+CysD levels and the use of the DL-HMTBA source promoted increased mRNA expression of the MTRR (p = 0.02), CBS (p = 0.09) and GSS (p = 0.06) in the broiler livers at 49 days of age. However, for ACHY, MTR, MAT1A and BHMT genes, there were no changes in expression (p ≥ 0.10) at any level or source studied. Met+CysD deficiency impaired performance and altered mRNA abundance by increasing gene expression of sulfur amino acid metabolism in broiler liver tissue at 42 days of age.