Risk factors for downer cow syndrome.

A nested case-control study to detect risk factors for the development of the downer cow syndrome 30 d postpartum was conducted. Records from 2705 lactations from 12 Holstein dairy herds in the vicinity of Cornell University were collected prospectively between March 1981 and April 1985. Logistic regression was used to model the risk factors for downer cow syndrome. No confounding or modification effect by season of calving and parity was detected. The cumulative postpartum incidence rate for downer cow syndrome was 1.1%. Clinical hypocalcemia and stillbirth increased the risk of downer cow syndrome fivefold. An interaction term existed between dystocia and retained placenta.