This experiment was designed to evaluate the influence of prepartum vitamin A supplementation on incidence of mastitis in Holstein cows.

Forty two cows were randomly distributed into blocks according to the parity and divided in two treatments:

control and supplemented with 180,000IU vit.A/day. The supplementation started 30 days before probable parturition date up to parturition. The Tamis test was performed weekly for clinical mastitis detection, and milk samples were collected for somatic cell counts. Vitamin A treatment decreased the incidence of clinical mastitis (P<0.05), however no effect on milk somatic cell count was observed.