Replacement Nellore heifers receiving supplementation under different herbage allowance: effects on forage characteristics, performance, physiology, and reproduction

•Grazing management alters canopy structure and forage nutritional value.•Grazing management impact animal performance and change heifer’s carcass traits.•Supplementation mitigates the negative effects of low herbage allowance on performance.•Low herbage allowance increases blood urea nitrogen and changes liver gene expression.•Blood urea nitrogen may affect the reproductive performance of Nellore heifers. In Brazil, heifers typically calve at 36–48 months. Due to the high demand for meat and the need to reduce slaughter age, high supplementation has become commonly used in beef cattle farming. However, the literature remains scarce on studies that explore the impact of grazing management during the background phase on the productivity and reproductive efficiency of young Nellore heifers. This study aimed to evaluate the effects of two-herbage allowances (HA) on forage characteristics, performance, physiology and reproductive parameters of replacement Nellore heifers. Ninety weaned heifers [169 ± 19 kg of shrunk body weight (SBW); 210 ± 28 days of age] were blocked by initial BW and randomly assigned to receive different HA: (1) High herbage allowance (HHA: 7.2 kg DM/kg BW) and (2) Low herbage allowance (LHA: 3.3 kg DM/kg BW); and divided into six paddocks, totaling 12 paddocks. The experimental period was divided into the growing phase (D173) and the reproductive season (D83). Continuous stocking with a variable stocking rate was used. The supplement was provided daily with expected intake of around 10 g/kg of BW. The HHA pasture showed greater values of canopy height, greater HA, and lower values of CP and CP: in vitro digestible DM ratio than the LHA pasture over the days of the study (P ≤ 0.05). Herbage mass and the green stem proportion were lower in LHA pasture (P