Three groups of 10 ewes each were treated with Repromap sponges (MAP), Chronogest sponges (FGA) or Controlled Drug Release devices (CIDR) for 11 days. At withdrawal the delay time until oestrus, LH surge and ovulation was measured. There was no significant difference between the two sponge treatments in mean delay times although FGA treated ewes tended to be less variable in their activity. CIDR treated ewes commenced standing oestrus sooner than MAP and FGA treated ewes (30h vs 42h and 40h respectively P<0.001). Similarly the onset of the LH surge (31h vs 46h and 46h P<0.001) and ovulation (59h vs 69h and 71h P<0.001) occurred sooner in the CIDR ewes compared to MAP and FGA sponges.

RJ, Martin, CJ Korte, DG McCall, DB Baird, PCD Newton, and ND Barlow

Proceedings of the New Zealand Society of Animal Production, Volume 51, , 25-33, 1991
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