The effects of post-partum drops in body condition on indices of energy metabolism in mid-lactation Holstein cows

Background: Evaluation of energy metabolism indices in mid-lactation Holstein cows is critical to monitor health status. Aims: The objective of this study was to assess the effects of low (≤0.75) vs. high (>0.75) drops in body condition score (BCS) until day 60 post-partum on energy metabolism indices during mid-lactation in Holstein cows. Methods: Twenty-eight Holstein cows were included in the study from the day of calving to day 120 of lactation. Whole blood samples were taken on 60, 90, and 120 days in milk (DIM). Serum was analyzed for insulin, glucose, non-esterified fatty acids (NEFA) and beta-hydroxybutyrate (BHB) levels. Results: In cows with low BCS drop (LoD group), insulin did not change significantly through days 60 to 120 of lactation, but increased in high drop cows (HiD group) (P<0.001). Glucose concentrations decreased linearly in the LoD cows (P=0.039) and showed a quadratic increase in the HiD group on day 90 (P=0.028). Concentrations of non-esterified fatty acids showed both linear (P=0.04) and quadratic (P=0.002) changes in the HiD group. The HiD cows had significantly higher concentrations of insulin on day 120 (P=0.017) compared to the LoD group. Glucose concentration was lower (P<0.01) in HiD cows on 60 DIM. The concentration of non-esterified fatty acids was higher in HiD cows on day 90 (P<0.01). Surrogate indices of insulin resistance (calculated based on the concentrations of the measured metabolites) were different between the groups on day 90, indicating decreased insulin sensitivity in the HiD cows. Conclusion: Greater depletion of body reserves during early lactation may result in some inconsistencies in energy metabolism during mid-lactation periods. Controlling BCS loss during early lactation may help alleviate such alterations possibly through modifying insulin sensitivity of the tissues.