Effects of month and PMSG on the interval from CIDR removal to
ovulation in Romney and Merino ewes
T.W. Knight, K. O'Neill, M. Ridland, G. Hamilton, A. Death, T.
Wyeth
AgResearch, Flock House Agricultural Centre, Private Bag 1900,
Bulls, New Zealand
Proceedings of the New Zealand Society of Animal Production.
1992, 52: 261-264
Five groups (15-30) of Romney or Merino ewes were synchronised
with CIDR devices for 12 days in March or April. In all but one group
of Romney ewes 400IU PMSG was injected at CIDR removal. Intervals to
onset of oestrus and ovulation were determined by recording crayon marks
and laparoscopy respectively every 4 hours. Interval to ovulation was
not affected by ewe breed or month of treatment, but it was 7.9 hours
earlier in ewes injected with PMSG (48.9h vs 56.8h P<0.001) and the
variance was less (13.4h vs 35.7h P<0.05). Interval to oestrus was
affected by breed of ewe, date of synchronisation and use of PMSG.
Keywords: NZSAPAB;
Oestrus; ovulation; Merino; Romney
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Last Updated 25-01-1997
