Rumen microbial counts and in vivo digestibility in buffaloes and cattle given different diets

Ruminal bacterial counts and in vivo digestibility were determined on four Mediterranean buffalo bulls and four Friesian bulls, all fistulated at the rumen, and given at maintenance level (50 g/kg M(0.75) per day of dry matter) four different diets with the same crude protein content (N X 6.25 = 140 g/kg dry matter) and with forage:concentrate ratios as follows: diet D12.5 = 0.875:0.125; diet D25.0 = 0.75:0.25; diet D37.5 = 0.625:0.375; diet D50.0 = 0.5:0.5. All the animals received the diets during four consecutive periods in a Latin-square design. Buffaloes had higher total microbial counts (10.78 v. 10.08 log10 cells per g dry rumen content, P < 0.01) as compared with cattle; differences in total ruminal bacterial counts among the diets were only observed within the buffalo species (diet D12.5 v. diets D25.0, D37.5, D50.0 : 10.04 v. 10.92, 10.98, 11.17 log10 cells per g dry rumen content, P < 0.01) and when comparing the two species for each diet, significantly higher values for bacterial counts in buffaloes were found for diets D25.0 : 10.92 v. 10.28 (P < 0.05), D37.5 : 10.98 v. 10.08 (P < 0.01) and D50.0 : 11.17 v. 9.76 (P < 0.01) log10 cells per g dry rumen content. Cattle showed significantly higher digestibility values for : organic matter (0.696 v. 0.676, P < 0.05), neutral-detergent fibre (NDF; 0.548 v. 0.511, P < 0.05) and cellulose (0.621 v. 0.509, P < 0.01), while the crude protein digestibility (CPD) values were similar (0.667 and 0.671). Comparing the two species for each diet, cattle showed significantly higher digestibility values for organic matter in diet D50.0 only (0.714 v. 0.688, P < 0.01), for NDF in diet D12.5 only (0.578 v. 0.531, P < 0.05) and for cellulose in all diets (0.660 v. 0.546, 0.630 v. 0.525, 0.605 v. 0.505, 0.588 v. 0.460, P < 0.01); in contrast buffaloes showed higher values of the CPD for diet D12.5 (0.662 v. 0.632, P < 0.05).