This work was carried out to evaluate the forage particle passage rates and ingestive behavior of dairy heifers from three genetic groups Holstein (H) and Zebu (Z) cattle (7/8HZ, 15/16HZ, Graded Holstein - GH), kept in feedlot regime and submitted to diets, in a total mixed ration, with two fiber levels (30 and 60%) of neutral detergent fiber (NDF), using chopped Elephant grass (Pennisetum purpureum, Schum., cv. Mineirão) as forage. The experiment was conducted in a 3 × 2 factorial arrangement (genetic group × fiber level), in a completely randomized design, with four replicates. The digestive kinetic trial was determined in the end of the experimental period in a completely randomized design with three replicates. Rumen-reticulum retention time (RRRT) was 13.8% lower and cecum-colon retention time (CCRT) was 13.9% higher for the diet with 30% NDF in relation to the diet with 60% NDF. There was a higher spending time with feeding, rumination and total chew, while the ingestive rate and rumination rate of DM were lower for the 60% NDF level in the diet. As for genetic groups, RRRT was 14.75% higher for the 7/8HZ heifers than for GH, and CCRT was 28.2% lower for 7/8HZ heifers. Graded Holstein heifers spent more time in activities of feeding and chewing, however, with lower intake rate than 7/8HZ heifers.
chewing time; elephantgrass; particles rate; ruminal kinetics; ruminating chew
