Extent of fibre digestion by pure isolates of ruminal fibrolytic bacteria in lactating buffaloes.

The present study was carried out to isolate fibre degrading bacteria from the rumen of buffaloes. The bacterial isolates were screened for their ability to degrade pure wheat straw fibre and selected isolates were further characterized on the basis of their morphology, biochemical properties and molecular nature. The most potent fibrolytic bacterial isolate was studied in detail as probiotic in lactating Murrah buffaloes to see the effect on nutrient utilization, milk production and on ruminal microbial population as well as on survivability of inoculated isolate during the 90 days lactation trial. Total forty two numbers of bacterial isolates were isolated from buffalo rumen liquor by using Hungate’s anaerobic roll tube technique and were tested for their fibre degrading potential on pure NDF showing fibre digestibility, ranges from 47.00 to 63.48 percent respectively. Twelve potent selected fibrolytic bacterial isolates were assayed for their fibrolytic enzyme activity like carboxymethylcellulase, avicellase, β-glucosidase, xylanase and acetyl esterase at 24, 48, 72 and 96 hours of incubation at 39C using pure NDF as substrate. The isolate NB-1 showed maximum mean carboxymethylcellulase, β-glucosidase and xylanase activity. Based on morphological, biochemical and molecular characterization, selected potent isolates of fibrolytic bacteria were found to be of genus Ruminococcus. Molecular characterization and sequencing result of three most potent fibrolytic isolates showed similarity with the Ruminococcus flavefaciens strains. The three selected bacterial isolates were then tested for their ability to degrade high fibre diet (R:C: 80:20) individually as well as in combination. The isolate NB-1 showed the highest digestibility of 57.83 percent among all individual isolates and combination of isolates and also showed highest PF and MBM (mg) value of 2.11 and 69.12, respectively. On the basis of in vitro studies and enzyme profile, the isolate NB-1 was selected for feeding as inoculum for lactating Murrah buffaloes during experimental trial. The selected isolate NB-1 sequence showed 97% similarity of 16S rRNA gene sequences with Ruminococcus flavefaciens strain FD-1. Isolate NB-1 was cultured anaerobically and 300 ml of live bacterial culture was given to treatment group of lactating buffaloes orally alternate day for one month continuously whereas, control group of animals was given the same amount of autoclaved culture. Results of lactation trial showed that buffaloes maintained their body weight in both groups and the difference in fortnightly mean body weight changes remained similar between the groups. Average daily milk yield ranged from 5.91 to 6.65 kg/day/animal in the treatment group and 5.88 to 6.36 kg/day/animal in the control group, respectively during different fortnights. The difference in mean dry matter intake was found significant (P<0.05) between treatment group (11.77 kg/day) and control group (11.11 kg/day) during the experimental period. The digestibility of NDF and ADF was found to be higher in the treatment group by 9.66 and 19.20 percent over the control group although the effect was not significant. The quantification studies showed that there was a significant (P<0.05) increase in total fungal and total bacterial population as well as inoculated isolate bacterial group population in the treatment group during the dosing period. However, decreasing trend was noticed during post-dosing period except inoculated isolate bacterial group population which remained unchanged.