Direct and carry-over effects of supplementation on growth performance, metabolic profile, and intramuscular adipogenesis of grazing beef heifers

This study evaluated the direct and carry-over effects of nutritional strategies during the suckling and backgrounding phases on performance, blood metabolites, and gene expression related to lipid metabolism in grazing F1 Red Angus × Nellore heifers. Thirty-four female calves were assigned in a 2 × 2 factorial design: with or without creep feeding during the suckling phase and low or high level of supplementation during backgrounding. All animals were finished on intensive grazing in a common nutritional treatment. Performance traits, blood parameters, muscle ether extract content, and the expression of adipogenic and lipogenic genes (ZFP423, PPARγ, ACC, CPT1β, PGC1α) were assessed. Creep feeding increased weight (P = 0.073) and average daily gain (ADG) (P = 0.079) at weaning, and altered lipid and nitrogen metabolism markers, including reductions in cholesterol (P = 0.007), HDL (P = 0.004), and creatinine (P = 0.03), and increase the serum urea nitrogen (P < 0.10). During backgrounding, high level supplementation improved body weight (P = 0.04), ADG (P = 0.02), and increased concentrations of glucose (P = 0.07) cholesterol (P = 0.01), triglycerides (P = 0.001), albumin (P = 0.01), and IGF1 (P = 0.01). No interactive effects between phases were observed (P > 0.10). In the finishing phase, slaughter body weight was affected (P = 0.04) being higher in animals previously fed high level. No effects of supplementation strategy were detected on carcass traits, muscle ether extract, or gene expression. These results indicate that early-life supplementation improves intermediate performance and metabolic status, but does not alter carcass composition or intramuscular fat gene markers at slaughter.