Can blood metabolites, body condition and milk production be used to predict reproductive performance in dairy cows?

Spring-calving Holstein-Friesian cows (n=127) on two farms were monitored monthly between calving and first service for blood metabolite concentrations, body condition and milk production. Following hormonal synchronisation, cows were artificially inseminated and examined by transrectal ultrasonography approximately 30 days after service to determine pregnancy rate. Animals were retrospectively divided into two groups for post-hoc statistical analysis: cows that conceived to first service, 55 per cent (70/127) and cows that failed to conceive to first service, 45 per cent (57/127). Cows that conceived and cows that did not conceive to first service did not differ significantly in mean milk production, peak milk production, body condition score and blood concentrations of albumin, urea, glucose, non-esterified fatty acids, bile acids, or activities of alanine aminotransferase, aspartate aminotransferase and glutamate dehydrogenase between calving and first service. At first service, blood protein and globulin concentrations were significantly higher (P<0.05) and blood beta-hydroxybutyrate concentrations were significantly lower (P<0.05) in cows that did not conceive. However, all blood metabolite concentrations were within the normal range. It was concluded that milk production, body condition score and blood metabolite concentrations recorded monthly between calving and first service were not reliable predictors of conception rates at first service.