Effects of various lighting regimens and pinealectomy on semen production in Romney rams.

ABSTRACT

Sixteen Romney rams were utilized in a 2 x 2 factorial experiment designed to evaluate the effects on semen production of (i) contrasting lighting regimens, and (ii) pinealectomy or sham-operation. Reversal of the annual photoperiodic cycle advanced the seasonal peak of fructose levels in semen by 4 months and also reduced percentages of unstained and morphologically normal spermatozoa. Pinealectomy abolished this advancement of peak fructose production and reduced overall concentrations and motility of spermatozoa. Moreover, towards the end of the study pinealectomized rams had higher ejaculate volumes than did sham-operated rams. Testicular and accessory sex gland data obtained after the rams were killed showed a marked influence of the lighting regimen high values from sham-operated rams in short daily photoperiods contrasted with depressed values from those in long daily photoperiods. Pinealectomized rams provided values midway between these extremes, a finding which suggested both anti- and pro-gonadotrophic roles for the pineal gland in rams.