RESUMEN
The objective of this study was to evaluate the effects of physically effective neutral detergent fiber (peNDF) in rice straw and cassava pulp diets on the chewing activity, ruminal fermentation, milk production, and digestibility in low-producing dairy cows. Eight lactating Holstein crossbred cows were randomly divided into two groups in a crossover design with two dietary treatments over two 21-day periods. The difference in peNDF contents was achieved by balancing the ratio of rice straw, cassava pulp, and concentrate. The high cassava pulp diet had 15.5% peNDF and the low cassava pulp diet had 20.2% peNDF. The results showed that feeding the low cassava pulp diet increased the concentrations of milk protein, milk fat, solids-not-fat, and total solids in the milk. In contrast, the dry matter intake, milk yield, lactose content, chewing activity, nutrient digestibility, ruminal fermentation, and pH were not affected by treatments.