Proceedings of the New Zealand Society of Animal Production.
1986, 46: 153-156
Proceedings of the New Zealand Society of Animal Production.
1986, 46: 153-156
The aim of the present study was to examine the influence of the ram on plasma FSH concentrations in progesterone-primed Romney ewes which were: (1) anoestrous; (2) devoid of ovaries; (3) or anoestrous but induced to ovulate by a pulsatile injection regimen of luteinising hormone (LH).
The results showed that there was an abrupt fall in the mean FSH levels in anoestrous or LH-pulsed ewes at 1 hour after ram introduction and that this level of suppression (~40%) was maintained for ~22 hours in anoestrous ewes and for 12 hours in LH-pulsed ewes. Also, an FSH reduction (~20%) was observed in the ovariectomised ewes. In the anoestrous ewes, the FSH changes were observed without any associated oestrous or ovulatory behaviour. In the LH-pulsed group, all ewes showed oestrus and 75% produced normal corpora lutea.
Collectively, the evidence suggests that when attempts are made to achieve fertile matings in hormone-treated anoestrous ewes, there may be advantages in delaying ram introduction until ~24 hours after progesterone withdrawal.
Keywords: NZSAPAB; Plasma FSH; sheep; ewes; rams; oestrus induction
