Effect of steroid immunisation and vaginal artificial insemination on the fertility of synchronised ewes

R.W. Moore, P.R. Lynch, C.M. Miller and R.A. Welch

Whatawhata Hill Country Research Station, Ministry of Agriculture and Fisheries, Hamilton and Ruakura Animal Research Centre, Ministry of Agriculture and Fisheries, Hamilton

Proceedings of the New Zealand Society of Animal Production. 1987, 47: 147-150

Romney ewes were used for a 2 x 2 factorial trial, 2 injections (boosted) v 1 injection of Fecundin(r) pre-artificial insemination (AI) x controlled internal drug releaser (CIDR) re-insertion v no CIDR reinsertion post-AI. The ewes were all synchronised with CIDRs for the AI carried out intravaginally without a speculum 52 h after CIDR withdrawal. Those ewes failing to conceive to AI were naturally mated at the next oestrus.

Fecundin(r) boosting decreased the percentage of CIDR synchronised ewes becoming pregnant to AI (12.6 v 21.3, P<0.01) but increased multiple pregnancy rate (50.4 v 30.2, P<0.001) at the subsequent natural mating. Reinsertion of CIDRs for 5 to 8 d, 9 to 12 d after removal of the first CIDR had no effect on pregnancy rate to AI. The response to Fecundin(r) boosting in terms of multiple pregnancy rate at the natural mating was essentially the same in light ewes as in heavy ewes.

Keywords: NZSAPAB; Ewe; Romney; steroid immunisation; artificial insemination; CIDR; fertility; prolificacy

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Last Updated 03-05-1997