| Endometritis is a common postpartum disease in dairy cows,which seriously affects the production performance and reproductive performance of dairy cows and leads to great economic losses in dairy farming.Delayed clearance of pathogenic bacteria in uterus is an important factor causing childbirth,while dystocia is closely related to childbirth,but the specific mechanism has not been clarified.So calving quantity,newborn weight,calf sex,calf status and pregnancy index of 1079 cows in a large dairy farm in Ningxia were collected from January to December,2021.Factors affecting dystocia by SPSS software and the influence of dystocia on the incidence of endometritis.The relationship between the incidence of dystocia,endometritis and the structure of uterine flora was analyzed.by 16 S r RNA gene highthroughput sequencing.Then P.succinatutens and E.rectale strains were screened out from the sequencing results.The preventive effects of P.succinatutens and E.rectale strains on LPS-induced inflammatory reaction of dairy endometrial epithelial cells were studied by bacterial cell co-culture flow cytometry and Real-time PCR.The following results are obtained:(1)By analyzing the factors affecting dystocia,it was found that calving month,calf birth weight,calving number,calf sex and calf survival status were significantly correlated with the occurrence of dystocia,while parity was not correlated with the occurrence of dystocia.Among them: time shows that December-January is the high incidence season of dystocia;the number of calves showed that the dystocia rate of twin cows was higher than that of single cows.The birth weight of calves showed that the dystocia grade of cows with body weight over 50 kg increased.Calf sex and survival status indicated that cows with female calves were more likely to have natural childbirth,while cows with stillbirth were more likely to have dystocia.In addition,the conception rate showed a downward trend with the increase of dystocia grade,and dystocia had no effect on the number of mating times and the number of days without pregnancy.The occurrence of dystocia leads to an increase in the prevalence of endometritis,and with the increase of dystocia grade,the incidence of endometritis gradually increases.(2)In order to study the relationship between dystocia,endometritis and microbial flora.40 uterine lavage fluid samples of dystocia healthy cows(DH),dystocia endometritis cows(DE),non-dystocia healthy cows(NDH)and non-dystocia endometritis cows(NDE)were collected at 28 days and 45 days postpartum.The results of operational taxonomic units(OTUs)showed that the number of OTUs in the healthy group was significantly higher than that in the endometritis group.With the prolongation of postpartum days,the number of unique OTUs in the healthy group gradually decreased,while the number of unique OTUs in the endometritis group gradually increased.Beta diversity analysis showed that there was a significant difference in diversity index between healthy cows and endometritis cows at 28 days postpartum.The results of species composition showed that the proportion of the top five bacterial genera in the relative abundance of each group gradually decreased with the prolongation of postpartum days.The proportion of non-refractory healthy dairy cows decreased from 25.18 % to 16.60 %,and the proportion of non-refractory endometritis dairy cows decreased from 73.31 % to 29.60 %.However,the proportion of dystocia healthy dairy cows decreased from 44.18 % to 35.44 %,and the proportion of dystocia endometritis group decreased from 66.16 % to 62.92 %.Therefore,dystocia caused the loss of uterine microbial heterogeneity and the decrease of bacterial richness.Wilcox test showed that the abundance of P.succinatum and E.rectale strains in the uterus of dystocia and non-dystocia healthy cows was higher than that of endometritis group.(3)The effects of P.succinatutens and E.rectale strains on endometrial epithelial cells and LPS-induced inflammatory responses in dairy cow endometrial epithelial cells were evaluated by co-culture of bacterial cells using cow endometrial epithelial cells.Flow cytometry showed that P.succinatutens and E.rectale strains had no significant effect on apoptosis of endometrial epithelial cells,and Real-time PCR results showed that P.succinatutens and E.rectale strains significantly reduced the rise of IL-1β,IL-6 and IL-8 at m RNA levels caused by LPS.In summary: December-January is the high incidence season of dystocia.With the increase of dystocia grade,the incidence of endometritis gradually increases,and the conception rate gradually decreases.The loss of microbial heterogeneity and the decrease of bacterial abundance in the uterus of dairy cows caused by dystocia are risk factors for endometritis.In addition,the inhibitory effect of P.succinatum and E.rectale strains on LPSinduced inflammatory factors in bovine endometrial epithelial cells was preliminarily explored from the m RNA level,which provided new ideas for the prevention and control of endometritis and laid a theoretical foundation for the next clinical treatment.Continuing to explore more evidence that E.rectale and P.succinatutens become potential probiotics and verify their prevention and control of endometritis in dairy cows is our next stage of work. |
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