Effect of concentrate diet on epigenetic marks of Longissimus thoracis muscle tissue of Nellore cattle and their relationships with carcass aspects and meat quality

Abstract

In beef cattle, different nutritional strategies can be used in the rearing phase, aiming at greater efficiency in the growth of calves and reproductive aspects of matrices. In this sense, replacement or supplementation of the base diet can be used, as occurs, respectively, in early weaning and creep-feeding. Such managements can positively affect carcass finishing at the end of the rearing cycle, as well as being a determining factor in improving the health of calves and, consequently, their well-being. Despite being a widespread technology with demonstrated effects on the performance of cattle, there are few studies that have evaluated the effect of creep-feeding on metabolism in Nellore cattle, and there is even less with regard to identifying brands. epigenetics that may be effectively related to these metabolic alterations. Thus, this study will aim, from the Longissimus thoracis muscle, to characterize gene regions, genes and regulatory elements linked to histone modifications and methylated cytosines (5'mC), as well as to identify those that are proportionally different between treatments proposed, namely, groups of non-supplemented and supplemented Nellore calves through the creep-feeding system mutually combined with rearing and semi-intensive (supplemented) or extensive (not supplemented) finishing. For this, 96 male Nellore calves, offspring of four different bulls, approximately 60 days old, and with an initial body weight (BW) of 75 kg will be used. The trial period will be divided into two phases: Phase 1 - breeding (240 days); Phase 2 - rearing and termination (679 days), totaling 919 days. The design used will be completely randomized blocks in a 2x2 factorial scheme, with factor 1 supplementation in the brood (mineral salt - SM vs. creep-feeding) and factor 2 nutritional strategies in growing and finishing (intensive vs. extensive). The treatments will be: T1 or intensive creep - CI) calves on pasture receiving creep-feeding (5 g/kg BW) from day 60 to 240 (180 days) in Phase 1 and energetic protein supplement (10 g/kg BW) in Phase two; T2 or extensive creep - CE) calves on pasture receiving creep-feeding (5 g/kg BW) from day 60 to 240 (180 days) in Phase 1 and protein supplement (1 g/kg BW) in the dry season, SM (ad libitum ) in the waters, protein supplement (1 g/kg BW) in the dry season and energetic protein supplement (3 g/kg BW) in autumn in Phase 2; T3 or without intensive creep - SI) calves on pasture receiving SM (ad libitum) from day 60 to 240 (180 days) in Phase 1 and energy protein supplement (10 g/kg BW) in Phase 2, and T4 or without extensive creep - SE) calves on pasture receiving SM (ad libitum) from day 60 to 240 (180 days) in Phase 1 and protein supplement (1 g/kg BW) in the dry season, SM (ad libitum) in the waters, protein supplement (1 g /kg BW) in the dry season and energy protein supplement (3 g/kg BW) in the fall in Phase 2. Weighings, carcass ultrasonography (US) and collection of muscle biopsies and blood samples will be performed at the beginning of supplementation, at weaning and close to slaughter. The collected tissues will be used for DNA extraction and sequencing in order to detect epigenetic marks significantly associated with different treatments, in which regions of the genome linked to H3K27ac and H3K4me3 histone marks will be prospected through ChIP-Seq, and differentially methylated regions through RRBS technique. After slaughter, samples (steaks) of the TL will be collected between the 12th and 13th ribs of the left half-carcass, from which meat quality parameters will be determined. Finally, integrated analyzes of molecular data, as well as meat quality, will be performed to infer important relationships between treatments, epigenetic modifications and carcass quality. (AU)