Serum vitamin D concentrations at dry-off and close-up predict increased postpartum urine ketone concentrations in dairy cattle

摘要

Vitamin D is commonly supplemented to dairy cowsas vitamin D_3 to support calcium homeostasis and intimes of low sunlight exposure. Vitamin D has beneficialimmunomodulatory and anti-inflammatory properties.Serum 25-hydroxyvitamin D [25(OH)D] concentrationsfluctuated during lactation, with the lowest concentrationsmeasured in healthy cows within 7 d of calving.However, it is unknown if serum 25(OH)D concentrationsmeasured during the previous lactation are associatedwith transition diseases or health risk factorsin dairy cattle. We collected serum samples from 279dairy cattle from 5 commercial dairy herds in Michiganat dry-off, close-up, and 2–10 d in milk (DIM). VitaminD concentrations were determined by measuring serum25(OH)D by radioimmunoassay. Total serum calciumwas measured by colorimetric methods. Body conditionscores (BCS) were assigned at the time of blood collection.Clinical disease incidence was monitored until 30d postparturition. Separate bivariable logistic regressionanalyses were used to determine if serum 25(OH)Dat dry-off, close-up, and 2–10 DIM was associated withvarious clinical diseases including mastitis, lameness,and uterine disorders (classified as metritis, retainedplacenta, or both) and increased urine ketone concentrationsat P < 0.05. Among all significant bivariableanalyses, multivariable logistic regression analyses werebuilt to adjust for potential confounding variables includingparity, BCS, season, and calcium. Receiver operatorcharacteristic (ROC) curve analyses were used todetermine optimal concentrations of serum 25(OH)D.We found that higher serum 25(OH)D concentrationsat dry-off and close-up predicted increased urine ketoneconcentrations in early lactation, even after adjustmentfor confounders. Alternatively, we found that lower serum25(OH)D at 2–10 DIM was associated with uterinediseases. Optimal concentrations for serum 25(OH)Dat dry-off and close-up for lower risk of increased urineketone concentrations were below 103.4 and 91.1 ng/mL, respectively. The optimal concentration for serum25(OH)D at 2–10 DIM for uterine diseases was above71.4 ng/mL. These results indicate that serum 25(OH)D at dry-off and close-up may be a novel predictive biomarkerfor increased urine ketone concentrations duringearly lactation. Increased urine ketone concentrationsare not necessarily harmful or diagnostic for ketosis butdo indicate development of negative energy balance,metabolic stress, and increased risk of early lactationdiseases. Predicting that dairy cattle are at increasedrisk of disease facilitates implementation of interventionstrategies that may lower disease incidence. Futurestudies should confirm these findings and determine theutility of serum 25(OH)D concentrations as a predictivebiomarker for clinical and subclinical ketosis.