Effect of different nutritional strategies at cow-calf on gene expression, DNA methylation and carcass and meat traits of Angus-Nellore crossbred cattle

Abstract

Different strategies have been used to increase the intramuscular fat deposition in meat produced in Brazil, mainly from Nellore (Bos indicus) and its crossings, aiming to improve the final product quality and thus meet more demanding markets. One strategy is the supplementation at cow-calf. Recent research has shown that the administration of intramuscular vitamin A at birth in Bos taurus calves may promote increased intramuscular fat content. However, there is no research evaluating the effect of vitamin A supplementation in the diet during creep feeding on epigenetic status, gene expression, and intramuscular adipogenesis and lipogenesis in Nellore calves and their crosses with taurine breeds (Bos taurus). Thus, this study aims to analyze the differences in gene expression in a broad way and the methylation patterns of the main differentially expressed genes in the weaning and slaughter phase of crossbred cattle submitted to different treatments between birth and 210 days of life. Will be used 72 male Angus-Nellore crossbred steers, not castrated, half-sibs, kept from 20 days of age until weaning under three different treatments (n = 24/treatment): group 1 (G1) - no supplementation in creep feeding; G2 - supplementation in creep without vitamin A e; G3 - supplementation in creep with 63.000 UI vitamin A. The animals will be weaned at 210 days, and then will be confined for 160 days in collective pens (three animals/pen) receiving a diet containing 12.6% roughage and 87.4% corn based concentrate. At weaning, aliquots of Longissimus thoracis (LT) muscle will be collected by biopsy. During the slaughter, aliquots of the LT muscle from the right half carcass and LT samples from the 12th to 13th ribs of the left half carcass will be collected. With the LT muscle samples on the left side of the carcass will be determined: loin eye area (AOL), subcutaneous fat coverage (EGS), marbling index (IM), total lipids (TL) and shear force (SF). From the LT aliquots of the biopsies and the right half carcass will be analyzed the differences in global gene expression and methylation patterns of the regulatory regions of the main differentially expressed genes. Therefore, mRNA sequencing techniques (RNA-Seq) and quantitative methylation specific PCR (qMSP) will be used. Differential gene expression will be analyzed between treatments (G1 vs G2, G1 vs G3, and G2 vs G3 - 10 individuals/group) at weaning and at slaughter and, also, in both moments within the three groups. In order to determine whether the differences in gene expression to be found are due to DNA methylation of regulatory gene regions, the qMSP analysis will be conducted with the top six differentially expressed genes between treatments at weaning and at slaughter. (AU)