Effects of Substituting Cassava Pulp with Broken Rice and Cassava Chips in Crossbred Holstein Diets: Rumen Fermentation, Enteric Methane Emission, and Energy Utilization

Abstract

This study evaluates the effects of substituting cassava pulp with broken rice and cassava chips in the total mixed ration silage diets of beef cattle on feed composition, ensiling quality, digestibility, and energy utilization. Fifteen Holstein Thai native crossbred (89% Bos taurus × 11% Bos indicus) steers in the fattening phase, with an average age of 2.5 ± 0.1 years and an initial body weight of 603.7 ± 14.3 kg, were used in the energy balance trial. Using a randomized complete block design with five replications, the steers received one of three treatments. The three dietary treatments included substituting cassava pulp with cassava chips and broken rice on a dry matter basis with ratios of 50:0:0, 30:20:0, or 10:20:20. The results show that broken rice is a superior nutrient source and provides greater energy balance (p < 0.01). Despite the cost implications, substituting cassava pulp and chips positively impacts the ensilage pH and reduces the acetic acid concentration (p < 0.01). There was an increase in the lactic acid bacteria count (p < 0.05) and a reduction in the rumen ammonia, propionate, and butyrate concentrations (p < 0.05) without adverse effects (p > 0.05) on digestibility, blood metabolites, or enteric methane emissions. These findings suggest that broken rice is a promising alternative grain-rich ruminant feed. Future research should explore on-farm long-term feeding and economic evaluations to provide a more comprehensive understanding of the practical implications.