Effects of diagnostic low-volume uterine lavage shortly before first service on reproductive performance, culling and milk production

The objective was to evaluate if uterine sampling by low-volume uterine lavage, done shortly before the end of the voluntary waiting period, affected reproductive performance, milk production, or culling. Approximately 20 cows (40 and 60 d postpartum) were sampled in each of 38 herds (total, 752 cows), whereas all remaining cows concurrently between 40 and 60 d were a non-sampled reference cohort (n = 2,252 cows). There was an interaction between parity and sampling for first-service conception, calving to conception interval, and milk production. When stratified by parity, there was a tendency for impaired reproductive performance in sampled primiparous cows compared with non-sampled primiparous cows (Odds Ratio for pregnancy to first-service = 0.78 (95% C.I. 0.58-1.04). The Hazard Ratio for pregnancy in sampled primiparous cows was 0.89 (95% C.I. 0.77-1.04) compared to non-sampled primiparous cows. Sampling did not affect first-service conception rate (Odds Ratio for pregnancy Odds ratio (OR) for pregnancy = 1.03; 95% C.I. 0.80-1.33) or calving-to conception interval in multiparous cows (Hazard Ratio = 1.04; 95% C.I. 0.91-1.18). Sampling did not affect culling risk (Hazard Ratio HR = 0.92; 95% C.I. 0.77-1.11) after accounting for covariates. After stratification by parity, milk production was not affected by sampling except in fourth- and fifth-parity cows where sampled cows produced more milk than non-sampled cows after controlling for first test-day milk production and days-postpartum at first test-day. In conclusion, sampling by low-volume uterine lavage did not have significant detrimental effects on reproduction, culling, or milk production. However, there was a tendency for lower first-service conception in sampled primiparous cows, but the procedure appeared to be benign in multiparous cows.