Application of probiotics in the vaginal tract modulated bacterial composition in transition dairy cows
Uterine infections are highly associated with infertility, which is the main reason for culling of dairy cows. The objective of this study was to test whether intravaginal infusion of probiotics could modify the bacterial composition of the vaginal tract of transition dairy cows. One hundred pregnant Holstein cows were randomly (based on parity, body condition score, and milk yield) assigned to 3 groups 2 wk before the expected day of parturition (wk 0) as following: 1) a dose of probiotics on wk -2 and -1 and a dose of carrier (sterile skim milk) on wk +1 (TRT1); 2) a dose of probiotics on wk -2, -1, and +1 (TRT2), and 3) a dose of carrier on wk -2, -1, and +1 (CTR). Probiotics were a culture mixture of 3 lactic acid bacteria (LAB) composed of Lactobacillus sakei FUA3089, Pediococcus acidilactici FUA3138, and FUA3140, which were infused at 108-109 cfu per dose. Vaginal mucus was collected once a week on wk -2, -1, 0, +1, +2, +3 and +8. Vaginal pH was monitored once a week from wk -2 to +3; vaginal microbiota were monitored by quantitative PCR. At wk +3, compared with the control group, TRT1 increased the gene copy number of Lactobacillus group by 3 log (P < 0.01), L. sakei by 1.5 log (P < 0.05), and Enterococcus spp. by 2.5 log (P < 0.01). Meanwhile, TRT2 increased the the number of L. sakei by 2.5 log relative to the control group (P < 0.05). No difference was observed among treatment groups in terms of gene copy numbers of total bacteria, Bacteroides group, Bacillus spp., Staphylococcus spp., Enterobacteriaceae, E. coli and pediocin structural gene pedA. The canonical score plot demonstrated that the gene copy numbers of Lactobacillus group discriminated best for TRT1, whereas those of L. sakei and Bacillus spp. discriminated best for TRT2. The bacterial composition of CTR was not discriminated by any of the bacterial populations determined. No differences were observed among treatment groups regarding the vaginal pH of periparturient dairy cows. In conclusion, vaginal infusion of probiotics around calving modulated the vaginal microbiota of dairy cows as indicated by alterations in the number of Lactobacillus group, L. sakei, and Enterococcus spp.
Keywords: bacterial composition, dairy cow, probiotics, vaginal tract