Suplementación con grano de arroz con cáscara en régimen de autoconsumo a terneros pastoreando raigrás: Efecto sobre el consumo, la selección, y el comportamiento

The objective of this study was to evaluate the effect of supplementation with whole rice grain with husk (WRGH) and its method of delivery on intake and behavior of Hereford calves aged 9 months and weighing 170 kg ± 20 kg grazing ryegrass. The experiment was conducted at the Intensive Beef Production Unit (UPIC) of EEMAC in Paysandú, Uruguay, using 36 calves allocated to three treatments: no supplementation (Control), daily supplementation at 1.0% of body weight (DS), and ad libitum self-feeding supplementation (SF), all with a forage allowance of 2.5% of body weight. Supplement use significantly reduced forage intake by 18.5% when comparing supplemented animals with the control (P < 0.05), with a greater reduction observed in SF (33.34%). Regarding forage selection, calves supplemented ad libitum consumed forage with a higher crude protein content than that originally offered. In terms of animal behavior, the control group showed a higher probability of grazing (50%, P < 0.01) compared with the other treatments. Among supplemented animals, those in DS spent more time grazing than SF (35%, P < 0.01). No significant differences were observed in rumination activity between supplementation methods, although rumination time was greater in supplemented animals than in the control. Residual biomass was 56.8% higher in supplemented treatments, indicating lower forage utilization. This difference was especially marked in SF, where forage utilization was estimated at 38.3%. In comparison, the DS treatment showed a utilization of 52.1%, while the control reached 62.9%. In conclusion, supplementation with WRGH particularly under ad libitum conditions reduced forage intake and grazing time, while increasing pasture selectivity. This resulted in greater supplement intake, higher forage substitution, and lower efficiency of forage utilization.