Mating Romney ewes in November-December using CIDRs and pregnant
mare serum gonadotrophin
T.W. Knight, W.H. McMillan, S.G. Kannegieter, E.S. Sorensen,
C.J. Ridland and M. Gibb
Batchelar Agricultural Centre, PO Box 1654, Palmerston North;
Whatawhata Hill Country Research Station, Private Bag, Hamilton and
Flock House Agricultural Centre, Private Bag, Bulls
Proceedings of the New Zealand Society of Animal Production.
1989, 49: 255-260
Mature Romney ewes were involved in three experiments at Flock
House Agricultural Centre and Limestone Downs (near Raglan) to identify
factors affecting the percentage of ewes pregnant to mating in November
and December following treatment with CIDRs and PMSG. Dorset rams were
no better than Romney rams for mating and increasing the ram percentage
from 10% to 15% failed to overcome the low conception rate of 50-65%.
Rams that had been used for mating 11 days previously increased the
percentage of ewes pregnant. Ewes previously lambing in autumn had only
a 4.8% increase in ewes mated and pregnant compared with ewes previously
lambing in spring. Despite the reuse of CIDRs reducing the percentage
of ewes mated by 6.1% it was still economical to reuse CIDRs. There was
a consistent increase in ewes pregnant and multiple pregnancies with
increasing dose of PMSG. By contrast live weight had no effect on the
reproductive performance of ewes except for those ewes less than 40 kg
live weight. Regulin implants failed to overcome the low conception
rate of ewes mating following treatment with CIDRs and PMSG in December.
Keywords: NZSAPAB;
Out-of-season breeding; pregnant mare serum gonadotrophin; PMSG;
CIDRs; oestrus; conception rates; Romney ewes
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Last Updated 18-03-1997
