Seasonal variation in seminal parameters, testicular size, and plasma testosterone concentration in Iranian Moghani rams

The aim of the present study was to monitor seasonal variations in semen characteristics, testicular size, and plasma testosterone concentration in Iranian Moghani rams. An artificial vagina was used to collect semen from 10 rams (3–4 years of age), from November (autumn) 2008, to October (autumn) 2009. Testicular circumference was larger (P < 0.05) during late summer (September) to early autumn (November). Ejaculate volume, sperm density, progressive motility and the percentage normal sperm on the other hand were higher (P < 0.05) during autumn and lowest during winter (P < 0.05). The plasma testosterone concentration was higher during autumn (P < 0.05) than at any other time of the year, while the testicular circumference was positively correlated with the testosterone concentration, percentage live/normal sperm and semen concentration. The lowest level of lactate dehydrogenase (LDH) in the seminal fluid was recorded during early October (autumn) (1.52 U/mL) and the highest level in early spring (2.57 U/mL). The lowest levels of K+ and Na+ in the seminal fluid were recorded in spring (72.7 and 70.2 mg/dL, respectively). However, the variation of the highest levels was in late autumn (94.1 and 72.4 mg/dL, respectively), with the variation in the Na+ concentration being much smaller than that of K+. The correlation coefficient of the percentage live/normal sperm and sperm motility with seminal fluid K+ level (r = 0.61 and 0.49, respectively) and Na+ level (r = 0.48 and 0.34, respectively) were positive, with the LDH correlation being negative (r =−0.51 and −0.43, respectively) (P < 0.01). In spite of monthly variations in sperm quality and testicular measurements, the semen quality of the Moghani rams was within the range regarded as satisfactory for normal fertility. It would seem as if the best quality semen for long-term preservation of Moghani sperm is produced during autumn.