The objective of this trial was to evaluate the chewing activity of dairy heifers fed diets in which Tifton 85 hay (Cynodon dactylon (L.) Pear) was partially replaced by citrus pulp. Twenty-eight Holstein dairy heifers averaging 12 months of age and 184 kg of BW at the beginning of the trial were blocked by initial BW and, within each block (7 blocks), randomly assigned to one of the following four treatments: 0, 16.6, 33.3, or 50% of a concentrate based on citrus pulp that partially replaced Tifton 85 hay in the diet. Diets were formulated to be isonitrogenous. It was observed linear reductions at the time spent eating, ruminating, and total chewing time (min/day) when citrus pulp was increased in the diet. However, the number of chews during ruminating was not affected by partially replacing Tifton 85 hay with citrus pulp. Although eating and ruminating efficiencies increased linearly when expressed in g of DM/h, both variables did not differ when expressed in g NDF/h across treatments. Replacing Tifton 85 hay with citrus pulp decreased eating, ruminating, and total chewing times leading to significant changes in the overall chewing activity of dairy heifers.
chewing; feeding rate; feeding time; rumination time
