Effects of short-term feeding of different sources of fatty acids in pre-mating diets on reproductive performance and blood metabolites of fat-tailed Iranian Afshari ewes

The effects of dietary omega-3 and omega-6 fatty acids (FAs) in pre-mating diets on reproductive performances and metabolic status of ewes have not been well investigated. Therefore, this study investigated the effect of supplementing different source of FAs on different aspects of reproductive performance of fat-tailed Iranian Afshari ewes. Thirty-two cycling, multiparous Afshari ewes were divided into four groups and fed one of the isocaloric and isonitrogenous diets supplemented with Sunflower oil (SFO), Fish oil (FO), calcium salt of palm oil (CaPO) and/or an equal mixture of SFO + FO (SFOFO). One day after the start of the flushing, the estrous cycles of all ewes were synchronized using 12-day CIDRs. After detecting signs of estrous, all ewes were mated with rams for 2 days. The examination of ovarian follicles was done by a transrectal ultrasonography. After counting all visible follicles, they were classified into 3 classes based on their diameters: small (≤3 mm), medium (3–4 mm) and large (≥4 mm). The results showed that fat sources had no impact on dry matter intake (DMI) and body condition score (BCS) of animals (P > 0.05). Plasma glucose, total cholesterol, and albumin concentrations also were not significantly affected by supplemental fat sources (P > 0.05). Plasma insulin levels were higher at the end of the flushing (on the day of CIDR removal) and the day of mating for ewes on CaPO diet (P < 0.05). Plasma estradiol-17β concentration was greater on the day of mating for ewes fed FO (P < 0.05). Progesterone levels in pregnant ewes fed FO were higher 30 d after mating (11.02 ng/mL; P < 0.05). Dietary treatments had no significant effect on number of small, medium and total follicles as well as the average size of small and medium follicles at the end of the flushing and the day of mating. The number of medium follicles on the day of oestrus (mating) were significantly higher for the ewes fed FO or SFO diets (P < 0.05). Likewise, the mean number and size of large follicles at the end of flushing and the day of oestrus were higher in ewes on FO diet (P < 0.05). Lambing rate and twinning rate increased (P < 0.05) in ewes fed FO or SFO, respectively. In conclusion, supplementation of n-3 PUFA rich FA especially FO in pre-mating diets showed beneficial effects on some indices of reproductive performance of Afshari ewes including lambing and twining rate due to higher number of medium sized follicles and size of the ovulatory (large) follicles at the day of oestrus and increased plasma progesterone levels in pregnant ewes.