The effect of dose level of steroid immunogen on the reproductive performance of ewes

J.F. Smith, L.T. McGown

Ruakura Animal Research Station, Ministry of Agriculture and Fisheries, Hamilton

Proceedings of the New Zealand Society of Animal Production. 1986, 46: 165-170

A major constraint on the profitability of using 'Fecundin(r)' is the cost of treatment and one approach to this problem is to reduce the dose rate. In 1984 Coopworth ewes were allocated to 3 groups. One group was untreated (control) while the other 2 groups were injected twice with Fecundin. One treated group received a full dose (2ml) each time while the other group received a half dose (1ml) on both occasions. In 1985 the same ewes were roboosted with Fecundin(r). Control ewes remained untreated while ewes from each group in 1984 were boosted with either a half or full dose.

In the first year, both immunised groups showed a substantial increase in ovulation rate over controls (2.45 full, 2.20 half and 1.86 control). The higher ovulation rate of full dose compared to half dose ewes did not result in more lambs born or weaned (lambs born/ewes joined were 1.68 full, 1.65 half and 1.35 control). In 1985 all 4 treatment groups had a higher ovulation rate (2.43) than the control (2.03 and there were no difference between immunisation treatments. A similar patter was seen in lambs born.

Thus the cost of treatment can be halved by using a 1 ml dose of Fecundin(r) without a drop in the additional performance obtained.

Keywords: NZSAPAB; Steroid immunisation; Fecundin(r); Coopworth; dose rate; reproduction; ewes; lambing; ovulation rate

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Last Updated 18-03-1997