EFFECT OF GENOTYPE ON RUMEN MICROBIAL-POPULATION OF BULLS CONSUMING SUGAR-CANE COLLECTING CENTERS RESIDUES

Four rumen cannulated bulls stabulated in a sugar cane collecting center during the dry season were used to determine the effect of genotype on the rumen microbial population. The genotypes evaluated were: A) Holstein and B) Zebu. The samples of rumen liquid were collected at 0, 2, 4 and 6 hr after feed supply. The experimental results are analysed according to a hierarchical linear model. model controlled genotype, animals within genotype, time and genotype x time interaction effects. Zebus had a higher total microbial mass (P < 0.05). Cellulolytic bacteria were 23.97 and 18.17 x 10(-6) c.f.u/ml for Zebu and Holstein, respectively. Proteolytic and amilolytic bacteria were twice and four times higher in Holstein than in Zebu. No genotype effect on protozoa were found except Dasytrichas which were more numerous (P < 0.01) in Zebu. It is concluded that the Zebu is mon resistant to the conditions imposed on the rumen by a low quality fibre diet such as residues from sugar cane collecting centres.