Temperament of Nelore growing-steers receiving supplementation in grazing system: performance, ultrasound measures, feeding behavior, and serum parameters

Abstract A study was performed to evaluate the temperament of beef cattle on grazing system regarding performance, ultrasound measures, feeding behavior, and physiological parameters. Twenty growing animals [Nelore; non-castrated males; 220 ± 33 kg initial body weight (BW); 10 ± 1 months of age] on rotational stocking system (Urochloa brizantha cv. Xaraes) were used. Individual temperament scores were calculated by averaging animal chute score and exit velocity score [adequate (ADQ) ≤ 3; or excitable (EXC) > 3] at the beginning of the trial period (d 0). At the same day, animals were ranked by temperament and BW, and assigned to receive (n = 10) or not (control = CON; n = 10) a supplementation (SUP). Body condition score (BCS), BW, hip height (HH), and ultrasound evaluations (ribeye area - uLMA; backfat thickness - uBFT) were recorded on d 0 and 84. Difference between BW (d 84 and 0) were used to determine the average daily gain (ADG). Blood samples were collected at 0, 28, 56, and 84 d and analyzed for serum cortisol, insulin, and haptoglobin. Feeding behavior data (time of grazing, rumination, resting, and drinking water) were obtained by all-animals scan sampling (4 d; 24-h per day). No interactions of temperament with supplementation were detected for performance. ADQ animals had a greater initial and final BW (P ≤ 0.032), and ADG (P = 0.031) than EXC animals. No differences were found for the other growth performance variables studied regarding temperament classification. SUP group had greater values for final BW (P