LAUSR

The objective of this study was to compare periparturient serum Ca dynamics (CaDyn) in cows with and without diseases in early lactation. The study enrolled 1,949 cows from a commercial dairy farm in northern Germany. Blood samples were drawn 7 d before expected calving date and on d 0, 1, 3, and 7 after calving and analyzed for serum Ca concentration. Cows were monitored for clinical hypocalcemia (CH), ketosis, left displaced abomasum (LDA), retained placenta, acute puerperal metritis (APM), mastitis, and pneumonia. To evaluate the association between CaDyn and diseases during the transition period, repeated measures ANOVA with first-order autoregressive covariance were performed. Serum CaDyn of healthy cows (i.e., without any of the aforementioned diseases) was compared with CaDyn of cows with one of the aforementioned diseases (CH, ketosis, APM, mastitis, LDA, and pneumonia), and cows with multiple diseases (CH+, ketosis+, APM+, mastitis+, LDA+, and pneumonia+). Separate models were built for primiparous and multiparous cows. For primiparous cows, we evaluated the association between CaDyn and ketosis (healthy cows vs. cows with ketosis vs. cows with ketosis+) and CaDyn and APM (healthy cows vs. cows with APM vs. cows with APM+). The same models were built for multiparous cows. Three additional models were built for multiparous cows to evaluate the association between CaDyn and CH (healthy cows vs. cows with CH vs. cows with CH+), mastitis (healthy cows vs. cows with mastitis vs. cows with mastitis+), or LDA (healthy cows vs. cows with LDA vs. cows with LDA+). In primiparous cows, serum Ca concentrations of cows with ketosis, APM, and APM+ were significantly reduced on d 3 and 7 after calving, compared with healthy cows. Serum Ca concentrations of primiparous cows with ketosis+ were reduced on d 3, but not on d 7 after calving. Multiparous cows with CH had significantly reduced serum Ca concentrations on d 0, 1, and 3 compared with healthy cows. On d 3 and 7, serum Ca concentration of CH+ cows was significantly reduced compared with healthy multiparous cows. Multiparous cows with ketosis and ketosis+ had significantly reduced serum Ca concentrations on d 1 and 3 compared with healthy cows. Cows with APM+ had significantly increased serum Ca concentrations on d 0 and reduced serum Ca concentrations on d 3, compared with healthy cows. Whereas multiparous cows with mastitis had a reduced serum Ca concentration on d 1, mastitis+ cows had a reduced serum Ca concentration on d 1 and 3, compared with healthy multiparous cows. Overall, multiparous cows with LDA+ had reduced serum Ca concentrations. Especially a delayed onset of hypocalcemia (d 3 and 7) was indicative for the development of disease in primiparous cows. In multiparous cows, reduced serum Ca concentrations on d 1 and 3 were associated with occurrence of diseases. Future studies should evaluate whether reduced serum Ca concentrations are a cause or concomitant circumstance of diseases in early lactation.