EFFECTS OF FEED AND WATER-DEPRIVATION ON RUMINAL CHARACTERISTICS AND MICROBIAL-POPULATION OF NEWLY WEANED AND FEEDLOT-ADAPTED CALVES

Two experiments were conducted to determine the effects of length of f eed and water deprivation on ruminal microbes and ruminal characterist ics. In Exp. 1, treatments were as follows: 1) weaned, but not trucked (0 h), 2) weaned, trucked, and fasted for 48 h (48 h), and 3) weaned, trucked, and fasted for 72 h (72 h). On d 0 (arrival back at the feed lot after treatment), DMI, ruminal volume (P < .05), and weight of rum inal contents (P < .05) decreased as length of feed and water deprivat ion increased. However, on d 4, there were no longer any differences ( P > .10) in DMI or weight of ruminal contents. On d 0, percentage of r uminal DM in the 48- and 72-h treatment groups was lower (P < .01) tha n in the 0-h treatment group, but there were no differences (P > .10) by d 4. After the steers used in Exp. 1 had been in the feedlot for 28 d, they were reallotted, and the three treatments (except for weaning ) were repeated; the 0-h group remained at the feedlot. On d 0, DMI of the 48-h group was lower (P < .05) than that of the 0-h group; DMI of the 72-h group was intermediate. On d 0, the 0-h treatment group had a greater ruminal DM percentage than the 48- and 72-h treatment groups (P < .05); however, due to large within-treatment variation the total weight of ruminal contents did not differ (P > .10) among treatments. There were no decreases (P > .10) in cellulolytic or total bacterial concentration or in the ruminal numbers of cellulolytic or total bacte ria due to length of feed and water deprivation on d 0 in either Exp. 1 or 2. In both trials, 48 and 72 h of feed and water deprivation decr eased (P < .05) protozoal numbers on d 0 and 4 compared with the 0-h t reatment group.