Evaluación del grano de arroz con cáscara como suplemento para terneras Hereford pastoreando raigrás Bill Max durante invierno en sustitución del grano de sorgo

The objective of this work was to evaluate the substitution of sorghum grain with rice grain with husk (RGWH) on winter supplementation response in calves grazing Ryegrass. The experiment was conducted in paddock number 6 of the Intensive Meat Production Unit (UPIC) located at the Experimental Station "Dr. Mario Alberto Cassinoni" (EEMAC) Faculty of Agronomy, Paysandú; Uruguay. Thirty-six Hereford heifers born in the spring of 2021, belonging to the experimental herd of EEMAC (140 kg ± 13.3 kg), were assigned to 9 groups, and these to 1 of 3 treatments: exclusive grazing of Bill Max ryegrass at a forage allocation (FA) of 2.5% of live weight without supplementation, or supplemented with sorghum grain or rice grain with husk. Grazing was carried out in 7-day occupation plots, adjusting the FA of each plot weekly based on the availability of ryegrass dry matter and the average weight of the animals in each plot. The supplement was provided daily in the morning at a rate of 1 kg/100 kg LW (dry basis). The experiment was analyzed using a randomized block design with repeated measures over time. When the treatment effect was significant, means were compared using orthogonal contrasts, evaluating the effect of supplementation and the effect of the type of supplement. Supplementation improved daily live weight gain (58 vs. 289 g/day, P<0.01), with higher ADG in the sorghum-supplemented treatment than in the RGWH-supplemented treatment (312 vs. 266 g/day, P<0.05), with a conversion efficiency of 6.5 and 7.78, respectively. The total dry matter intake of supplemented animals was 61.8% higher than non-supplemented animals, with no statistical differences in forage and supplement intake between the different treatments. Finally, it was observed that control animals tended to increase grazing activity, although there were no significant differences between treatments for both grazing and rumination. In the case of bite and rest rate, animals supplemented with RGWH showed higher activity. In conclusion, winter supplementation improves ADG in heifers grazing Bill Max ryegrass at a FA of 2.5% LW. This response will be greater when using sorghum grain compared to RGWH.