Monitoring the body condition score (BCS) of dairy cows is a management strategy that can assist dairy producers in decision-making. The BCS and its variations reflect the level of body fat reserves and fat mobilization throughout the different stages of lactation. Cows that mobilize excessive amounts of fat reserves in response to the increased energy requirements of the transition period are more likely to have higher beta-hydroxybutyrate (BHB) concentration in blood, leading to a higher incidence of hyperketonemia postpartum. In this study, our main objective was to evaluate how both BCS (at 21 d prior to the expected calving date, −21 BCS) and change in BCS during the late dry period (−21 d to calving, ∆BCS) are associated with temporal patterns of blood BHB concentrations during the first two weeks of lactation. Our secondary objective was to characterize the relationship between the change in BCS in the late dry period, and milk yield and milk composition in the first milk test postpartum. In this retrospective cohort study, we assessed BCS at 21 (±3) days before the expected calving date and within three days after calving. Blood BHB concentration was measured at days 3 (±1), 7 (±1), and 14 (±1) postpartum. Hyperketonemia (HYK) was defined as blood BHB ≥ 1.2 mmol/L. To evaluate how −21 BCS and ∆BCS during the late dry period were associated with BHB in early lactation, linear mixed-effects regression models with an unstructured covariate matrix were performed. The association between ∆BCS and incidence of postpartum HYK were determined using a multivariable log-binomial model. A linear regression model was used to evaluate the association between ∆BCS and milk yield and milk composition in the first monthly test-day. Covariates used for model adjustment include parity, season, and baseline BCS. We observed that cows with BCS ≥ 4.0 at 21 d before their expected calving date had the highest BHB concentration postpartum, but no evidence that BCS ≥ 4.0 at 21 d was associated with fluctuations of BHB over time. Cows that experienced a large BCS loss (larger than 0.5 units) during the late dry period had a 61% (95% CI: 1.04, 2.50) higher risk of developing HYK in early lactation and had higher BHB concentrations during early lactation compared with cows with no ∆BCS prepartum. These associations were observed independently of the BCS at −21 d prepartum (baseline). In addition, cows that lost more than 0.5 BCS unit in the late dry period produced 3.3 kg less milk (95% CI: −7.06, 0.45) at the first milk test compared to cows that had no ∆BCS during the late dry period. No evidence of an association between −21 BCS and ∆BCS in the late dry period and milk composition was observed in our study. These results suggest that dynamic measures of BCS during the late dry period, such as ∆BCS, are better at evaluating blood BHB patterns in early lactation than BCS measured at a single time point. Cows with larger BCS loss during the late dry period and with greater parity are more likely to have higher concentrations of blood BHB postpartum, with the highest concentrations reported at 7 d post-calving.

Hyperketonemia (HYK) is an early lactation metabolic disease frequently observed in high-producing dairy cattle and it has been associated with suboptimal reproductive performance, decreased milk yield, increase occurrence of other diseases, and increase in culling. The majority of the reports so far focused on the association of HYK and these outcomes during early lactation, however, the effect of HYK in the whole lactation and following lactations has not been as extensively characterized. Therefore, our primary objective was to evaluate the association of HYK occurring during the first 10 days after calving and culling in Holstein dairy cows throughout an entire lactation. Our secondary objective was to determine the likelihood of the occurrence of HYK in subsequent lactations in Holstein dairy cows.

Calcium (Ca) homeostasis is one of the many metabolic challenges faced by a dairy cow during her transition from the dry period into lactation. The use of anionic salts during the dry period is an effective strategy to prevent clinical hypocalcemia, yet subclinical hypocalcemia (SCH) has been reported to affect up to 70% of multiparous cows. Although the use of oral calcium supplements immediately after calving is a commonly adopted method to prevent and treat SCH in multiparous cows, there is a shortage of information comparing different oral calcium products. Thus, the overall goal of this project is to evaluate the effect of different commercially available oral calcium products on postpartum serum calcium profiles of dairy cows. Additional objectives are: determine milk production, urine pH, and Ca concentrations during the first 5 days after oral calcium supplementation. This study is ongoing, with serum and urine samples currently being analyzed to determine Ca concentrations.