Diurnal Effects on Serum Testosterone and Spermiogram of the West African Dwarf (WAD) Sheep During the Early Rainy Season

Circulating serum testosterone and seminal ejaculate characteristics of eighteen sexually mature WAD rams were evaluated at three diurnal phases: in the morning (6-8am), afternoon (12-1pm) and evening (4-6 pm). The ambient, as well as the rectal temperature of the rams were recorded. Significant differences were observed in the mean ambient temperatures during the three diurnal phases (p< 0.05). However, there was no significant change in mean rectal temperature of the rams among the three diurnal periods (p>0.05). Serum testosterone concentrations were 22.72 0.12 ng/ ml, 21.68 0.14 ng / ml and 21.15 0.10 ng/ml at 6-8am, 12noon-1pm, and 4-6 pm respectively. Significant differences were also observed during these three diurnal phases (p<0.05). However, seminal ejaculate characteristics such as concentration, percent live spermatozoa, and spermatozoa morphological defects did not vary significantly (p>0.05) between the diurnal phases. This study has shown that there are diurnal effects on serum testosterone concentrations. We therefore suggest that these effects be taken into consideration during natural breeding program(s) as sexual activity or increased libido is probably better expressed during the cooler periods of the day. Nigerian Veterinary Journal, VOL:32 (4) 336-341