the effect of melatonin on testicular circumference and semen characteristics in non-breeding season in lori-bakhtiari ram

background: this study was conducted to evaluate the effect of melatonin on semen quality and quantity changes and increase of reproductive efficiency in lori-bakhtiari ram in the non-reproductive season. objectives: the purpose of this study was to investigate the effect of melatonin on testicular size and semen qualitative and quantitative changes in the non-breeding season is lori-bakhtiari rams. methods: this study was designed to evaluate the effects of melatonin on the quantity and quality of semen and testicular diameter in 8 lori- bakhtiari rams (4 control rams and 4 treatment rams) for 10 weeks during spring 2013. each ram in the treatment group was received three tablets of 18 mg implantable melatonin subcutaneously at the base of ear after 5 weeks from the start of the trial. results: semen parameters and testicular diameter measurements were evaluated on a weekly basis. no significant differences were observed between 2 groups before melatonin implanting. a significant difference was observed after melatonin implanting between 2 groups in the mean of testicular diameter (treatment: 33.5±0.25 and control: 30.67±0.07 cm), in semen volume (treatment: 1.34±0.03 and control: 0.87± 0.04 ml) and in sperm concentration (treatment: 1.76±0.05 and control: 1.37±0.04 109/ml) (p0.05). conclusions: the results of this experiment showed that the use of melatonin in the non-reproductive season resulted in increase of testicular size, semen volume and sperm concentration in lori-bakhtiari ram. however, the rest of the semen parameters have not been affected.