Abstract: In the present work, the rams were divided into four groups of nearly equal average weights, during THE hot season of the year. The first group was kept without treatment as control. The second group was treated with selenium (0.1 mg / kg DM as sodium salenite) orally. The third group was injected with melatonin (25 Fg / kg body weight, daily at sunrise; melatonin was dissolved in a minimum of absolute ethanol and diluted in 0.9 NaCL 1: 9) and the fourth was injected with Prostaglandin F2% (PGF2%; 3 mg/head, one hour before collection of semen). The calculated temperature-humidity index (THI) value during the experimental period (25.6 with daylight length 14.05), indicated that the rams were exposed to very severe heat stress. The results showed that, in summer breeding season, rams injected with PGF2% and melatonin had significantly (P<0.05) lower rectal and skin temperature than in selenium and control groups, with the lowest values in PGF2% group.. The differences between selenium and control group were not significant in rectal temperature and between selenium and melatonin group in skin temperature. Scrotal-skin temperature was insignificantly affected by treatment. Rams injected with Prostaglandin F2% (PGF2%) surpassed (P< 0.05) the control group in sperm motility percentage and sperm-cell concentration (x109/ml), while the contrary occurred (P< 0.05) in reaction time, percentages of dead spermatozoa, sperm abnormalities and acrosomal damage. Rams treated with selenium had lower significantly (P<0.05) semen pH than in the other groups. Scrotal length was higher significantly (P<0.05) in rams treated with PGF2% or selenium than in control or melatonin groups. The differences between PGF2% and selenium and between melatonin and control groups, were not significant. Scrotal circumference and testes length were insignificantly affected by treatment. Blood components in rams, were insignificantly affected by selenium, melatonin or PGF2% treatments.
I.F.M. Marai , A.A. El- Darawany , E.I. Abou-Fandoud and M.A.M. Abdel- Hafez , 2003. Alleviation of Heat Stressed Egyptian Suffolk Rams by Treatment with Selenium, Melatonin or Prostaglandin F2% During Hot Summer of Egypt . Journal of Animal and Veterinary Advances, 2: 215-220.