Vitamin A supplementation during the weaning phase and restriction during the finishing phase: meat quality and lipogenic gene expression in F1 Angus - Nellore cattle

Abstract

Different strategies have been used to increase the deposition of intramuscular fat in beef in order to improve the quality of the final product and, thus, serve more demanding markets. One of these strategies is supplementation through creep feeding. Additionally, research has shown the benefits of supplementation (via intramuscular injection) with vitamin A at birth in F1 Bos taurus x Bos indicus cattle, with subsequent feedlot finishing. This strategy seems to favor the increase in the intramuscular fat content of meat. However, there are no studies that evaluate the effect of supplying supranutritional doses of vitamin A in the diet during the rearing phase through creep feeding on intramuscular lipogenesis in F1 Angus-Nellore young bulls. Thus, this study aim to analyze the differences in the expression of lipid metabolism genes in the weaning phase and in the slaughter of crossbred cattle submitted to different treatments between birth and 210 days of life. The animals used in this proposal will be the same as those of the FAPESP grant 2019/22621-3. Thus, 44 male F1 Angus-Nellore bulls, half-siblings, kept from 20 days of age until weaning under three treatments (n = 23 / treatment) will be used: group 1 (G1) - without supplementation in creep feeding (control); G2 - conventional supplementation in creep feeding and G3, creep feed concentrate enriched with vitamin A (63,000 IU). The animals will be weaned at 210 days, and then will be feedlot for 160 days in collective pens receiving a diet containing 12.6% roughage and 87.4% corn concentrate. At weaning, longissimus thoracic (LT) muscle aliquots will be collected by biopsy. During slaughter, aliquots of the LT muscle from carcass and samples of the LT between the 12th and 13th ribs of the left half carcass will be collected. The samples of the LT muscle on the left side of the carcass will determine ribeye area (REA), subcutaneous fat thickness (BFT), meat color, chemical composition, and shear force (SF). From the LT aliquots of biopsies and carcass, differences in gene expression will be analyzed using the RT-PCR technique. Target genes will be analyzed between treatments at the time of weaning and slaughter. (AU)