Effect of vitamin A or C on physiological and reproductive response of Rahmani ewes during subtropical summer breeding season

- Effects of vitamin A or C on heat tolerance and reproduction were studied in ewes.
- Vitamin A increased heat tolerance of Rahmani ewes at the beginning of summer season.
- Both vitamins improved metabolism of ewes around mating time and early pregnancy.
- Both vitamins enhanced progesterone concentration during early pregnancy.
- Vitamin A increased pregnancy outcomes during summer breeding season.

In the present study, 33 Rahmani ewes were equally divided into 3 groups: 1. Control group (non-treated ewes); 2. Vitamin A-group (supplemented orally one capsule containing 50 000 IU vitamin A/day); and 3. Vitamin C-group (dosed with 10 ml aqueous solution containing 3 g vitamin C/day). All ewes were run as one flock and kept under the conditions prevailing in the sheep-farm in summer. The vitamin treatment started in June and lasted for 50 days. Blood samples were collected and rectal temperature (RT) and ‎respiration rate (RR) were recorded at 8:00 a.m. and 1:00 p.m. every 10 days during the treatment period. The ‎temperature-humidity index (THI), coefficient of heat tolerance (CHT) and index of adaptability ‎ (IA) were calculated. Estrus was synchronized and ewes in heat were mated by ‎day 25 of the vitamin-treatment. Ultrasonic examinations of ovarian structures were carried out during ‎the follicular (day of estrus) and mid-luteal (day 7 post-mating) phases. Estradiol (E2) was determined on the day of estrus and progesterone (P4) was ‎determined on days 12 and 25 post-mating. Both vitamins did not affect heat tolerance parameters ‎including RT, RR, CHT or IA. However, both vitamins increased significantly ‎(P < 0.001) ‎ counts of erythrocytes (RBC) ‎and leukocytes (WBC). Either vitamin A or vitamin C decreased significantly (P < 0.01) mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH). Both vitamins ‎did not affect Hb concentrations or blood pH. Vitamin A treatment increased ‎ significantly (P < 0.05) total protein and globulin (P < 0.01) concentrations than vitamin C, whereas ‎they were intermediate in the control group. The greatest cholesterol concentration was significantly (P < 0.05) observed in ‎the vitamin C-group compared to other groups. The highest number ‎of large follicles (≥5 mm) and E2 concentration were significantly (P < 0.05) observed on the day of estrus in the vitamin A-group than the other groups. Both treatment groups had higher P4 concentration (P < 0.05) at the luteal ‎phase than the control group. The ewes that received an oral administration of vitamin A had the greatest (P < 0.05) lambing rate (no. of ewes lambed/no. of ewes exposed) and fecundity rate (no. of lambs born/no. of ewes exposed) compared to vitamin C or control group. Based on the present findings it is concluded that supplementing ewes in summer breeding season with vitamin A could be better strategy to increase reproductive efficiency.