Signaling pathways of adipogenesis and marbling in crossbred Bos taurus-Bos indicus cattle supplemented with vitamin A

Abstract

The low intramuscular fat (IMF) content in beef produced in Brazil contributes significantly to the lower value added in the consumer market. Several strategies have been proposed to increase the deposition of IMF, aiming to improve beef quality and meet the most specialized markets. This study will describe the signaling pathways of adipogenesis and marbling by transcriptome sequencing of steers that received vitamin A during the neonatal phase as a strategy to increase IMF deposition. In addition, differences in gene expression and DNA methylation patterns of muscle at weaning and adult stages will be investigated. Twenty male young F1 Nellore-Montana will be used in a randomized complete block design (light and heavy) with two treatments (with and without vitamin A). At birth, calves of vitamin A treatment will receive a dose of 30,000 IU. Biopsies will be conducted 30 days after birth and weaning for molecular biology analyzes. All animals will be immunocastrated through the application of anti-GnRF vaccine. The animals will be weaned with 210 days, and then feedlot finished for 150 days in individual pens receiving a diet containing 12.6% of silage and 87.4% of corn-based concentrate. Samples of the longissimus thoracis (LT) muscle will be collected between the 12th and 13th ribs of the left half carcass to analyze meat quality traits. Immediately after slaughter, LT samples will be collected from the right half carcass of these animals for molecular biology assays. The samples of the LT muscle on the left side of the carcass will be determined: shear force, cooking losses, marbling index, lightness, Chroma, Hue and chemical composition (lipid, protein, moisture and ash content). The molecular assay will use a transcriptome sequencing study (RNA-Seq) of the LT muscle, as well as methylation patterns of muscle DNA in the two stages (weaning and adult). The vitamin A injection after birth, a critical period of adipocyte formation, may increase IMF content in LT muscle of feedlot finished animals. Such changes will be studied in association with the molecular data in F1 Montana-Nellore crossbred steers. (AU)