Periparturient hypocalcemia in cows: effects on peripheral blood neutrophil and lymphocyte function.

Periparturient dairy cows are quite susceptible to intramammary infections and clinical mastitis, epidemiologic evidence indicates that parturient paresis (milk fever) greatly increases the risk of mastitis, although a causal relationship has not been established. In the present experiment the effects of hypocalcemia at parturition on the immune status of dairy cows were investigated. Ten healthy, multiparous Holstein cows were fed a high Ca diet prepartum to induce hypocalcemia at parturition. Five of these cows received intramuscular parathyroid hormone (crude synthetic N-terminus 1-34) to prevent hypocalcemia at parturition. Effects of hypocalcemia on various neutrophil and lymphocyte functions were determined during the periparturient period, ranging from 6 wk prepartum to 5 wk postpartum. All cows exhibited severe loss of immune cell function in the weeks surrounding parturition. Hypocalcemia or the development of parturient paresis did not exacerbate the immune cell dysfunction. This implies that the degree of hypocalcemia observed did not have a large or irreversible influence on neutrophil and lymphocyte function in periparturient cows.