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 cent er during the dry season were used to determine the effect of genotype on the rumen microbial population. The genotypes evaluated were: A) H olstein 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 bact eria were 23.97 and 18.17 x 10(-6) c.f.u/ml for Zebu and Holstein, res pectively. Proteolytic and amilolytic bacteria were twice and four tim es higher in Holstein than in Zebu. No genotype effect on protozoa wer e found except Dasytrichas which were more numerous (P < 0.01) in Zebu . It is concluded that the Zebu is mon resistant to the conditions imp osed on the rumen by a low quality fibre diet such as residues from su gar cane collecting centres.