This study was carried out in Holstein cows. Nine cows were fed with wheat straw and the others with hay from the 40(th) day of prepartum to the 21(st) day of postpartum. Blood samples were collected from the V. jugularis four times (3 weeks and one week before and 2 and 5 weeks after calving). Blood levels of GOT, GLDH, urea, Na, K, Ca, P, Mg, Cu, Zn, beta-carotene, vitamin A and E were determined. Ovarial cysts and disorders of reproductive performance were examined by rectal palpation every 10 days for 2 months.