Effect of fish meal and oil on hormone profile and reproductive variables in ewes inseminated by laparoscopy

• To assess the effect of fish oil and meal on reproductive variables on ewes.
• The time of onset estrus was delayed when ewes consumed fish oil and meal compared with a control diet.
• No differences were found in average P4 or INS concentrations in serum.
• Fish meal and oil did not affect pregnancy, but it did affect the prolificacy.

The addition of n-3 polyunsaturated fatty acids (PUFA) to the diet of ruminants can benefit the reproductive process in the female. The current study was conducted to assess the effect of a short period of feeding a diet that included fish meal and oil on the progesterone (P4) and insulin (INS) profile, and on reproductive variables including estrous onset, pregnancy and prolificacy in virgin ewes artificially inseminated by laparoscopy (AIL). Forty-two Dorset ewes were assigned into two experimental groups: These groups were no supplementation (CON; n=21) and a group supplemented with fish meal and oil (4 and 0.8%; FMO; n=21). Ewes were fed the experimental diets for 15 days, beginning four days before inserting sponges for estrus synchronization and ending the day the vaginal sponges were removed. Each ewe received 0.8 kg d−1 feed in individual pens. Ewes were pre-synchronized with prostaglandin F2α and later synchronized with chronolone sponges for 11 days. When sponges were removed, the ewes received 200 IU of eCG. The AIL began 48 h after sponge removal and estrus detection. The time of estrus onset was different among groups (P<0.05; CON: 35.1±2.1; FMO: 41.0±1.8 h). No differences were found in P4 (FMO: 3.8±1.2; CON: 3.5±1.4 ng mL−1) or INS concentrations in serum (FMO: 0.12±0.02; CON: 0.13±0.03 ng mL−1). Adding fish meal and oil to the diet did not affect pregnancy percentage (FMO: 52%; CON: 55%), but it did affect the prolificacy index (FMO: 1.63; CON: 1.25) (P<0.05). It was concluded that the addition of fish meal and oil to the diet of virgin ewes over a short period time delayed onset of estrus and enhanced prolificacy.