Influence of Vitamin B2, Ascorbic Acid and Melatonin on Ovarian Activities, Reproductive Performance of Ewes during the Summer Season under Subtropical Conditions

The present study was conducted to investigate the effect of different treatments (vitamin B2, ascorbic acid and melatonin) on ewes' fertility rates during summer under the local environmental conditions. The study was carried out on 42 mature cross ewes (3/8 Finnish X 5/8 Rahamani). Ewes were allocated into 4 groups: the first group (G1; n=11) injected with 2mL saline for 3 wk., served as control. The second (G2; n=10) and third group (G3; n=11) were injected intramuscular daily for 3 wk with 2 mL (15mg) of vitamin B2 and ascorbic acid, respectively. Ewes of the fourth group (G4; n=10) received twice daily subcutaneous injections of 0.5 mg melatonin at 8AM and 4PM at the dorsal surface of the ear for 3 wk. All treated groups (G2, G3, and G4) received 1g zinc chloride and 2.5mg chromium (Merck Millipore, USA) in form of 6 ml oral drench once per week for 3 weeks. All animals were checked for the onset of estrus 2 times daily using an intact ram and ewes were bred via natural mating using 3 rams. Laparoscopic examinations were carried out throughout the study for detection of ovulation rates. Results revealed that ascorbic acid resulted in a significantly (P<0.05) decreased mean interval (days) from treatment to estrus as compared with the control group (15.73±1.83 vs. 22.64±2.50, respectively). A remarkable improvement in the lambing rate in G2, G3 and G4 treated groups than in the G1 (80.0, 90.9, and 90.0 vs. 72.7%, respectively) was also observed. The ovulation rate was significantly (P < 0.05) elevated in G4 than that in G2 and G1 (1.60±0.16 vs. 1.20±0.13 and 1.14±0.00, respectively). The follicular development did notvary among groups. In conclusion, vitamin B2, ascorbic acid and melatonin have a beneficial effect on the reproductive performance of ewes during summer under subtropical conditions.