Antioxidant vitamins and lipid peroxidation status in noncyclic versus cyclic ewes subjected to ram effect, before mating

Abstract

This study assessed the levels of plasma vitamins A, E, and C and the lipid peroxidation status of cyclic and noncyclic ewes during pre-breeding week after a period of poor nutrition. The study was conducted on 100 crossbred fat-tailed adult ewes with body condition scores of 2.5 to 3.5, grazing on medium-to-low quality forages during summer. During 3 weeks of flushing, the ewes were fed alfalfa hay (40 %) and wheat straw (60 %) ad libitum plus 300 g of barley grain/head/day in addition to the available pasture. The ewes had been isolated for 2 months during summer and, thereafter, were kept in close proximity of the rams for 1 week before ram release. Whole blood samples were collected 7 days (day −7) and a few hours before ram release (day 1). Plasma progesterone (P4, marker of ovulation) and antioxidant vitamins and hemolysate malondialdehyde (MDA, marker of lipid peroxidation) were measured. Plasma P4 was also measured in an additional sample taken 14 days after ram release. Twenty-eight percent of ewes were noncyclic in both pre-breeding samplings (P4 ≤ 1 ng/mL). On day −7, the noncyclic ewes had higher levels of MDA (P = 0.027), but the antioxidant vitamins were not different between cyclic and noncyclic ewes (P > 0.05). On day 1, all antioxidant vitamins declined significantly in cyclic ewes, whereas they remained almost constant (P > 0.05) in noncyclic animals. At this time, MDA concentration increased in the cyclic ewes (P = 0.014). At day 14, after ram introduction, the proportion of noncyclic ewes reduced to 13 %. Oxidative stress may postpone the ewe’s cyclicity at the beginning of the breeding period but may be alleviated after a while. This may cause delayed conception and extended lambing periods. Ovarian cyclicity is capable of reducing the plasma levels of antioxidant vitamins and increases the level of lipid peroxidation.