The first two years' (1983, 1984) results of a trial to determine the effect of immunisation with Fecundin(r) on the reproductive performance of Romney, Coopworth and Perendale ewes under hill country conditions are reported. Immunisation increased ovulation rate by 40 to 60%, lambs born/ewe present at lambing by 19 to 26% and lambs present at weaning by 4 to 9%. The major reason that the increased potential lamb production of the immunised ewes was not realised in practice was the failure of the ewes that lambed to produce as many lambs as expected from their measure ovulation rate. Immunisation tended to produce a larger increase in ovulation rate in Romneys than in Coopworth and Perendales and in older ewes than in younger. Lambs of immunised ewes had lower birth weights and higher mortality rates within each birth rank than lambs from non-immunised ewes.

JF, Smith

Proceedings of the New Zealand Society of Animal Production, Volume 45, , 171-177, 1985
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