Analysis of muscle growth, postmortem enzymatic proteolysis and tenderness of bovine L. thoracis muscle with different vitamin A-induced marbling scores

Abstract

In beef cattle, its common observe higher levels of marbling and less muscle development, which may result in leaner bovine carcasses. Some genetic, nutritional and management strategies have been proposed to increase the deposition of intramuscular fat (marbling) in animals, aiming to improve product quality and serve more demanding markets. The supplementation with vitamin A shortly after birth is considered a promising strategy for increasing adipogenesis and lipogenesis in muscle tissue, without, however, impair animal growth and carcass weight. However, the molecular mechanisms that induce the highest marbling scores without significant losses in muscle growth in animals supplemented with vitamin A at young phases is still poorly described. For this purpose, 40 male F1 Montana-Nellore cattle will be used, from birth to finishing phase, in a randomized block design (light and heavy) with two treatments (Control [C] vs. Vitamin A [Vit.A]). The animals in this study received an intramuscular dose of 300,000 IU after birth. The animals were weaned at 210 days and subsequently feedlot for 150 days. At slaughter, samples of the Longissimus thoracis (LT) muscle were collected from the left half-carcass for molecular biology analyzes. After boning, data on intramuscular fat (IMF) were obtained. Subsequently, samples of LT from animals of treatment C vs. Vit.A (IMF = 2.57% vs. 4.10%; P = 0.002, respectively) will be used in physical analysis (tenderness, cooking losses, luminosity, chroma and hue, at three aging times) and molecular biology assays. Muscle growth will be determined by the characteristics of carcass production, ribeye area, as well as by the identification and quantification of MyHC isoforms in SDS-PAGE electrophoresis gel. Additionally, a proteomic assay of these IMF contrasting animals will be conducted for marbling based on the separation of proteins by two-dimensional electrophoresis (2D-PAGE) and characterization of protein spots differentially expressed by mass spectrometry (ESI-MS/MS). (AU)