| The purpose of the present study was to investigate the influence of virginiamycin supplementation on ruminal fermentation and microbial populations in steers. Four ruminally cannulated steers (BW 559.4±30.1 kg) were used in a cross-over design experiment for a period of 28 days. The basal forage to concentrate diet ratio was 35:65 on dry matter basis. The experiment was consist of control treatment and treatment with control diet plus VM 30 mg?kg-1 concentrate (DM basis). Ruminal fluid was collected at 08:00 am prefeeding, at 12:00 am and 18:00 pm post-feeding on 27th and 28th days. The part of the pooled sample from rumen fluid was transferred to anaerobic culture by roll-tube technique and analyse for species-specific real-time PCR quantification. The remaining pooled rumen fluid sample was analyzed for pH, VFA, ammonia-N and L-lactic acid. The results showed that VM increased the ruminal pH (6.70 vs 6.63; P<0.05), but decreased the ammonia nitrogen (4.94 vs 6.19 mg?100 mL-1; P<0.01) and mean counts of amylolytic bacteria and proteolytic bacteria (P<0.01) as compared to the control. No difference was observed in the L-lactic acid concentration (1.39 vs 1.26 mmol?L-1) in rumen fluid among the control and VM receiving steers. Compared to control, the steers receiving VM has altered trend on quantification of Selenomonas ruminantium, Anaerovibrio lipolytica, Ruminococcus albus and Streptococcus bovis in the rumen fluid (0.5 |
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