RUMINAL CHARACTERISTICS, MICROBIAL-POPULATIONS, AND DIGESTIVE CAPABILITIES OF NEWLY WEANED, STRESSED CALVES

Eight ruminally fistulated steers, 7 to 8 mb old, were used in a compl etely randomized, 2 x 2 factorial experiment to determine the effects of energy density and protein source in receiving diets on in situ DM, NDF, and N disappearance, concentrations of ruminal bacteria, protozo a, ammonia, and pH. Two energy densities (1.80 and 1.48 Mcal/kg of NE( m)) and two protein sources (spray-dried blood meal [SDBM] and soybean meal [SBM]) were compared. Fistulated steers were weaned, transported by truck, and held in a sale barn before their arrival at the feedlot . On d 0 (day of arrival at the feedlot), DMI was 62% of DMI on d 7 af ter arrival. Overall, feeding a high-energy diet resulted in lower (P < .01) in situ DM disappearance (DMD) of orchardgrass than feeding a l ow-energy diet at both 24 and 48 h. In situ 24-h DMD averaged 46.6% on d -3 and 41.6% on d 0, whereas 48-h in situ DMD on d -3 and 0 average d 58.2 and 58.6%, respectively, indicating the ruminal microbial popul ation was not inhibited in its ability to digest available substrate. Additionally, there were no differences (P > .10) in 48-h in situ NDF disappearance between d -3 and 0 (58.8 vs 57.8%), respectively. No dif ferences (P > .10) occurred in the concentration of total bacteria, or cellulolytic bacteria, due to feed and water deprivation. Concentrati on of total protozoa was lower (P < .05) on d 0 than at any other time . Entodinium averaged 72.5% of genera before weaning, and more than 90 % of genera found on all treatments by d 21. Diplodinium and Epidinium percentages tended to decline after weaning. Isotricha concentrations were low and Dasytricha were eliminated after d 7. In conclusion, the concentration of ruminal bacteria and the ability to digest available substrate were not decreased immediately after weaning, trucking, and 24 h of feed and water deprivation.