Short communication: Meta-analysis on therapy of bovine endometritis with prostaglandin F_2α-An update

The objective of the study was to update a prior meta-analysis on the efficacy of the treatment of bovine endometritis with PGF_2α. Clinical endometritis in cattle is defined as the presence of a purulent or mucopurulent vaginal discharge after 20 or 26 d, respectively, postpartum. Although the prevalence and impact of this disease are well known, the questions of whether and how to treat endometritis are still controversially discussed. Hence, to ensure timeliness of scientific results, we updated an existing meta-analysis published in 2013 that showed no treatment effect of PGF_2α in cases of bovine endometritis. As in the prior meta-analysis, a comprehensive literature search was conducted. After applying specific inclusion and exclusion criteria, 3 trials remained that could be added to the 6 trials in the initial meta-analysis. Data for each trial were analyzed using the meta-analysis software Review Manager (version 5.3; The Nordic Cochrane Centre, Copenhagen, Denmark). Estimated effect sizes of PGF_2α were calculated on calving to first service interval (CFSI) and calving to conception interval (CCI). As revealed by the initial meta-analysis, PGF_2α treatment still had no effect on both reproductive parameters. Heterogeneity remained substantial for CFSI and CCI and even increased for CCI compared with the initial meta-analysis. Subgroup analysis, however, did not reveal a source of heterogeneity. In updating the meta-analysis, publication bias for trials reporting CCI became even more pronounced, suggesting that studies with higher standard error (i.e., usually smaller studies) that reported a prolonging effect on CCI after a PGF_2α treatment were less likely to be published. Finally, although the number of trials published on the chosen topic and their comparability are still limited, this update of our meta-analysis now provides results that are based on approximately twice the number of included cows. The overall outcome, however, has not substantially changed and a positive effect of a PGF_2α treatment in case of clinical endometritis could not be shown. Therefore, we do not recommend a treatment of bovine endometritis with PGF_2α as a means to improve reproductive performance.