Effect of Endometrial Sampling Procedures on Subsequent Pregnancy Rate of Cattle

SIMPLE SUMMARY: An important concern about conducting endometrial sampling procedures prior to breeding is the potential adverse effect on subsequent fertility of sampled cattle. Traumatic injury to the cervix and uterus and risk of introduction of infection caused by these sampling procedures may adversely affect the fertility of cattle sampled prior to breeding. To investigate this, a systematic review of publications assessing the impact of endometrial sampling on subsequent pregnancy rates was conducted. Analysis within the studies selected demonstrated that pregnancy rates were similar between sampled and non-sampled animals when procedures were performed before or around the time of breeding. Unfortunately, it was not possible to compare each sampling procedure between studies due to variation in sampling conditions (i.e., type of breed, age, reproductive status, and the sampling to breeding interval). We concluded that conducting these endometrial sampling procedures does not adversely affect subsequent fertility; therefore they could be used to more accurately identify cattle with a normal endometrium prior to conducting procedures such as embryo transfer. However, further studies with a much larger number of cattle are needed to verify the effects of endometrial sampling on pregnancy rates. ABSTRACT: Endometrial infections are a common cause of reproductive loss in cattle. Accurate diagnosis is important to reduce the economic losses caused by endometritis. A range of sampling procedures have been developed which enable collection of endometrial tissue or luminal cells or uterine fluid. However, as these are all invasive procedures, there is a risk that sampling around the time of breeding may adversely affect subsequent pregnancy rate. This systematic review compared the pregnancy rates (PR) of cattle which underwent uterine lavage (UL), cotton swab (CS), cytobrush (CB), cytotape (CT), or endometrial biopsy (EB) sampling procedures with those that were not sampled. Using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) protocol, relevant databases, including Pubmed, Web of Science, CAB Abstracts, VetMed Resource–Ruminants, and Scopus, were searched. The outcome measured was the pregnancy rate after the collection of endometrial sample(s). Seven studies, involving a total of 3693 cows, fulfilled the inclusion criteria for the systematic review and allowed the comparison of PR between sampled (n = 1254) and non-sampled cows (n = 2409). The results of the systematic review showed that endometrial sampling procedures can be performed before breeding or shortly after insemination without adversely affecting pregnancy rates in cattle. However, further studies are needed to validate this information.