This trial was conducted to evaluate the effects of replacing corn silage with sugarcane on intake, apparent digestibility of nutrients, ruminal pH and ammonia nitrogen, and ruminal passage rate of digesta in lactating dairy cows. Proportion sugarcane increased as follows: 0, 33.3, 66.6 and 100% of the forage portion of the diet. Twelve Holstein and crossbred Holstein/Zebu cows with potential yield varying from 5,000 to 7,000 kg of milk per lactation were randomly assigned to three 4x4 Latin squares. Cows were maintained in individual stalls and were fed ad libitum twice a day a diet containing a forage:concentrate ratio of 60:40 during the 84-days experimental period. Replacing corn silage with sugarcane linearly reduced the intakes of all nutrients with the exception of lignin and nonfiber carbohydrates. No significant effects on apparent digestibilities of dry matter, organic matter and crude protein were observed by replacing corn silage with sugarcane in this trial. However, neutral detergent fiber digestibility decreased and that of nonfiber carbohydrates increased when sugarcane replaced corn silage in the diet. Although ruminal pH did not differ among treatments, a significant quadratic response was found according to time after feeding. Significant quadratic responses were also observed for concentration of ruminal ammonia by increasing the proportion of sugarcane in the diet as well as time past the morning feeding. Ruminal passage rate of digesta decreased and average total retention time increased as sugarcane replaced corn silage, which possibly explains the observed reduction in dry matter intake. Therefore, it is recommended to include up to 33% of sugarcane in the diet of lactating dairy cows yielding 24 kg of milk per day.
intake; digestibility; ruminal pH; ruminal ammonia
