Evaluación del grano de arroz con cáscara (GACC) como suplemento ofrecido en autoconsumo a vacunos pastoreando raigrás: efecto sobre el consumo, fermentación ruminal, cinética de la degradación in situ y digestibilidad

The present study was conducted in paddock number 2 of the Intensive Beef Production Unit (UPIC) located at the “Dr. Mario Alberto Cassinoni” Experimental Station (EEMAC), Faculty of Agronomy, Paysandú, Uruguay. The objective was to evaluate the effect of supplementation with broken rice grain with husk (GACC) and its feeding method (daily at 1% of live weight or ad libitum self-feeding) on the degradation kinetics of the supplement and forage, ruminal fermentation parameters, and behaviour of steers grazing ryegrass during the autumn-winter period. Three Hereford steers, fistulated and born in the spring of 2022, from the experimental station's own herd were used. The steers had an average weight of 282.3 ± 18.9 kg at the beginning of the experiment. Animals were randomly assigned to each treatment using a Latin square design over three periods. The treatments applied were as follows: exclusive grazing of Jack cultivar ryegrass with forage allocation of 2.5% of live weight (LW) without supplementation, daily supplementation at 1% of LW with GACC, and ad libitum supplementation with GACC. Grazing was conducted in strips with weekly shifts, and supplementation was provided individually once a day in the morning. The variables evaluated for each treatment included dry matter (DM) intake, in situ degradability, in vivo digestibility of DM, ruminal pH and ammonia, and behaviour. No significant differences were observed among treatments in DM intake of GACC, forage, or total diet. Similarly, no differences were found in ruminal pH or ammonia levels. No significant differences were detected among treatments in organic matter and DM digestibility. However, differences were observed in the in situ degradability of DM of the feeds between the self-feeding and daily supplementation treatments. There is limited global research on the ruminal kinetics of GACC in livestock supplementation, which highlights the significance of this experiment in the field of animal nutrition.