Abstract :
The effects of different maternal uterine environments on the reproductive characteristics
of Cheviot and Suffolk ram lambs were investigated. Thirty-two, singleton, male lambs
born following AI and embryo transfer were allocated to four groups: Cheviot lambs born
to Cheviot ewes (CinC), Suffolk lambs born to Cheviot ewes (SinC), Cheviot lambs born
to Suffolk ewes (CinS) and Suffolk lambs born to Suffolk ewes (SinS). At days 120, 150,
180, 210 and 240 of age, the live weight (LW), scrotal circumference (SC), testis length
(TL) and testicular diameter (TD) of all lambs were recorded. From 150 days of age, semen
samples were collected by electro-ejaculation and characteristics of the spermatozoa evaluated,
including wave motion, semen density and sperm morphology for major and minor
defects. The mean lamb LW for the period between 120 and 240 days of age for the CinS
lambs (29.3 ± 1.64 kg) was significantly (p < 0.05) lower than the SinS (36.5 ± 1.40 kg). The
left and right TD in the CinC and SinS were significantly higher (p < 0.05) than for the SinC and
CinS lambs. Plasma testosterone concentrations for the SinC (260 ± 17 pg/ml) lambs were
significantly lower (p < 0.05) than in the other treatment groups. Scrotal circumference (SC),
left and right testicular length (TL), and semen characteristics were not significantly different
between the four groups of lambs. LW and semen characteristics significantly improved
as the lambs increased (p < 0.01) in age. With increasing age, the major and the minor morphological
defects of the spermatozoa significantly decreased (p < 0.01). Results suggest
that the pre-natal uterine environment does affect the live weight, testicular diameter and
blood testosterone, but has no effect on the semen characteristics of the post-natal lambs.
