ABSTRACT
The objective of this study was to determine the relationship of postpartum oxidative stress and the ovarian anestrus in the dairy cows. Sixteen cows showed normal ovarian cyclicity [normal estrous cycle] detected after 56-63 days postpartum and kept as G1. Thirteen cows showed ovarian cycle after 70-84 days postpartum, G2 and other ten animals showed marked delayed in the ovarian cyclicity more than 90 days, G3. Venous blood samples were taken weekly from all animals in the last two weeks of pregnancy and in postpartum period as well as, sera of blood samples were kept for measuring all parameters. Another blood samples from ten non-pregnant cows in diestrus were taken. The oxidative stress [lipid peroxides and nitric oxide], antioxidants [superoxide dismutase, vitamin E and selenium], as well as estradiol-17beta and progesterone were measured in all animals. In prepartum, lipid peroxides as well as nitric oxide were increased in the last week of pregnancy. In postpartum the preoxidative indices were elevated in the animals of G3 while antioxidants were decreased significantly in G3 and to some extend in G2. Estradiol-17 beta hormone levels were increased significantly in animals of G3 and it was negatively significant correlated with LPO and NO. While progesterone levels were positively significant correlated with antioxidants in the animals of G3. The oxidative stress in these animals may be led to follicular damage and failure of maturation and ovulation. It was concluded from this study that excess free radical production may be play a role in the prolongation of the postpartum anestrus in dairy cows. These may be due to exhaustion of antioxidant system in milk production. Therefore, it was advise to supplement the dam with antioxidants during the late stage of pregnancy and in the postpartum period to stimulate the normal ovarian activity