No change detected in body weight, scrotal circumference, semen characteristics and sexual behaviour during the development of prepubertal Milchschaf lambs after weekly administration of eCG.

To study the effects of equine chorionic gonadotropin (eCG) on pubertal development, 38 Milchschaf spring born male lambs fathered by the same ram and grazing over native pasture as a single mob during all the experiment were divided into three groups as follows: group 100 (100 IU of eCG weekly i.m., n = 11), group 400 (400 IU of eCG weekly i.m., n = 12) and group 0 (controls, n = 15). Lambs were weighed and scrotal circumference was registered every 2 weeks since birth until 170 days of age (end of experiment). On days 125 and 167 semen was collected using an electroejaculator. Semen volume and concentration, mass and individual sperm motility (scale 0 to 5) and total number of spermatozoa in the ejaculate were recorded. The sexual behaviour of the lambs was evaluated twice, on days 127 and 170 in a pen test with oestrous ewes. There were no significant effects of treatment on body weight or scrotal circumference, semen characteristics or sexual behaviour. At least in the administration regimens tested, eCG treatment has no effect on prepubertal reproductive development of male lambs.