This work wascarried out to evaluate the forage particle passage rates and ingestive behaviorof dairy heifers from three genetic groups Holstein (H) and Zebu (Z) cattle(7/8HZ, 15/16HZ, Graded Holstein - GH), kept in feedlot regime and submittedto diets, in a total mixed ration, with two fiber levels (30 and 60%) of neutraldetergent 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 completelyrandomized design, with four replicates. The digestive kinetic trial was determinedin the end of the experimental period in a completely randomized design withthree replicates. Rumen-reticulum retention time (RRRT) was 13.8% lower andcecum-colon retention time (CCRT) was 13.9% higher for the diet with 30% NDFin relation to the diet with 60% NDF. There was a higher spending time withfeeding, rumination and total chew, while the ingestive rate and ruminationrate 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 activitiesof feeding and chewing, however, with lower intake rate than 7/8HZ heifers.
