Ruminal cellulolytic bacteria and protozoa from bison, cattle-bison hybrids, and cattle fed three alfalfa-corn diets

Abstract

Ruminal cellulolytic bacteria and protozoa and in vitro digestibility of alfalfa fiber fractions were compared among bison, bison hybrids, and crossbed cattle (five each) when they were fed alfalfa and corn in a ratio of 100:0, 75:25, and 50:50, respectively. The total number of viable bacteria (2.16 × 109 to 5.44 × 109/ml of ruminal fluid) and the number of cellulolytic bacteria (3.74 × 107 to 10.9 × 107/ml) were not different among groups of animals fed each diet. The genera of protozoa in all of the animal groups were similar; however, when either the 100:0 or 50:50 diet was used the percentage of Entodinium sp. was lower and the percentage of Diplodiniinae was higher (P < 0.05) in bison than in bison hybrids or cattle. Bacteroides succinogenes made up the largest number of cellulolytic isolates from bison (58 and 36%, respectively, on the 100:0 and 75:25 diets), which were more numerous (P < 0.05) than those from bison hybrids (36 and 12%) and cattle (33 and 18%). This was offset by a lower number of cellulolytic Butyrivibrio isolates. The numbers of Ruminococcus albus and R. flavefaciens isolates, in general, were similar among the bovid species, although R. flavefaciens generally made up less than 10% of the cellulolytic isolates. In vitro digestibility coefficients were greater (P < 0.05) for the bison when the 75:25 diet was used and similar for the other two diets. The concentration of ruminal volatile fatty acids was larger (P < 0.05) in bison than in bison hybrids and cattle when the 50:50 diet was used. Results from this study indicate that the percentages of protozoan genera and cellulolytic bacterial species in bison are different from those of bison hybrids and cattle, suggesting that metabolic differences exist among these animal groups. © 1989, American Society for Microbiology.