Abstract
The objectives of this observational study were to determine the optimal progesteronemia threshold for defining anovulation at 50 days in milk (DIM) in dairy cows and to identify risk factors for this condition. A total of 3,776 cows from 100 Holstein dairy herds were enrolled in this cow-level study. During farm visits, cows were bled at 1-14DIM to quantify ketonemia and glycemia, examined at 30-43 DIM to diagnose purulent vaginal discharge, cytological endometritis, and leukocyte esterase endometritis, and were bled at a 14d interval to quantify progesteronemia. Multiple progesteronemia thresholds were tested to identify the one providing the highest sum of sensitivity and specificity to predict the pregnancy status at first service. The optimal threshold found for defining anovulation at 50DIM was ≤0.90 ng/mL. The final model for risk factors included parity group, season of calving, cytological endometritis, hyperketonemia, hypoglycemia, and the two-way interaction term of hyperketonemia and hypoglycemia. Overall, these results suggest that a progesteronemia threshold of ≤0.9ng/mL could be used to define anovulation at 50 days in milk in dairy cows.
Highlights
Cows with early resumption of ovarian cyclicity during the postpartum period were shown to have better subsequent reproductive performance than cows with postpartum anovulation [1,2,3]
The proportion of cows affected by dystocia, twinning, retained placenta, displaced abomasum, purulent vaginal discharge, cytological endometritis, and leukocyte esterase endometritis during the study were 3.8% (145/3,776), 6.9% (262/3,776), 6.0% (227/3,776), 5.1% (194/3,776), 5.5% (193/3,512), 29.3% (1,029/3,512), and 42.0% (1,475/3,512), respectively
Mixed multivariable logistic regression models allowed to determine that the optimal progesteronemia threshold to define anovulation at 50 days in milk (DIM) (±7) was ≤0.90 ng/mL
Summary
Cows with early resumption of ovarian cyclicity during the postpartum period were shown to have better subsequent reproductive performance than cows with postpartum anovulation [1,2,3]. Many studies investigating the prevalence, risk factors, and impact of postpartum anovulation have used progesterone concentrations (serum or milk) or ovarian ultrasonography to determine whether the cows are cycling or not [5,6,7] For those ones using progesteronemia, a common procedure in these papers is to consider cows anovular (or not cycling) if they have progesteronemia results < 1ng/mL [2,5,7]. The threshold of 1ng/mL is commonly used in studies but there is little evidence to support this as the optimal progesteronemia value for defining postpartum anovulation In other words, it remains unclear whether the use of this threshold is associated with the subsequent reproductive performance of dairy cows. Further research should investigate the optimal progesteronemia threshold for diagnosing postpartum anovulation
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