Submitted to: Frontiers in Veterinary Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/11/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Clinical metritis (CM) has significant costs to dairy producers, associated with decreased milk production, reduced reproductive performance, and treatment. Lack of treatment for metritis is seen as an animal welfare issue, as multiple studies conclude that metritis is associated with pain in cattle. The current treatment strategy involves systemic antibiotics; however, there is increasing public health concern about judicious antibiotic use and preventing multidrug-resistant pathogens. This study found that intrauterine treatment with dextrose had a higher clinical cure rate and no adverse effects on the naturally occurring vaginal microbiome compared to conventional antibiotics. Dextrose may be a low-cost antibiotic-free alternative that dairy producers can leverage to promote animal health and welfare in their herds.

Technical Abstract: Clinical metritis (CM) has significant costs to dairy producers, associated with decreased milk production, reduced reproductive performance, and treatment. The current treatment strategy involves systemic antibiotics; however, there is increasing public health concern about judicious antibiotic use and preventing multidrug-resistant pathogens. The objective of this study was to evaluate the effects of a nonantibiotic treatment vs systemic antibiotic therapy on the microbiome of the vaginal discharge of dairy cows diagnosed with CM at 7±3 DIM (days in milk). We hypothesize that both treatment methods will have a similar impact on the reproductive microbiome due to broad-spectrum bactericidal activity, and therefore, there will not be significant differences amongst the microbiota after the completion of therapy. Cows from a dairy in central Pennsylvania were screened for CM at 7±3 days DIM using a Metricheck™ device (n=351). Cows presenting with red-brown watery discharge were diagnosed with CM and eligible for enrollment. Eligible cows (n=77) were blocked by parity and randomly allocated to one of two treatments starting on the day of diagnosis: 1) Intrauterine dextrose (DEX, n=38): cows received one liter of an intrauterine 50% dextrose solution for three days, and 2) Systemic ceftiofur (CONV, n=39): cows received two injections of ceftiofur (6.6 mg/Kg of BW; Excede, Zoetis Inc.) 72 hours apart. Cows were evaluated for clinical cure rate at 7±3 and 14±3 days post-diagnosis. Vaginal discharge samples were collected using the Metricheck™ at enrollment day (study d 0, before treatment), study d 7, and study d 14 for a subset of enrolled cows (DEX=13, CONV=14). Vaginal discharge samples were analyzed with 16S rRNA gene sequencing to evaluate changes in the microbiome between treatments. The clinical cure rate at study day seven was 76.92% (10/13) for DEX and 71.43% (10/14) for CONV, and for study day 14, DEX was 11/13 (84.62%) and CONV was 13/14 (92.86%). Alpha diversity (richness and evenness of microbes within each sample) did not differ (Welch's t-test) between the treatments at any of the three time points. Beta diversity (comparison of microbial communities between cows) based on PERMANOVA analysis did differ between treatment groups at study d 0 (P=0.014) and again at study d 14 (P=0.028), but not at study d 7 (P=0.261). No taxa were significantly increased or decreased in relative abundance between the two treatment groups at any of the three time points (t-test). Though baseline beta diversity did differ, the microbiome of each group did not differ in any of the results at the time point immediately following treatment, which could indicate that each treatment has a similar impact on the microbiome. While 16S rRNA analysis does not provide information on the viability of bacteria, the relative similarity of the microbiome between the two groups immediately following treatment might suggest that intrauterine dextrose could be utilized as a low-cost antibiotic alternative treatment for CM.