Hormonal and ovarian responses in Romney ewe hoggets after
synchronisation and superovulation treatment.
J.W. Campbell, M.F. McDonald, G.A. Wickham
Department of Animal Science, Massey University, Palmerston North,
New Zealand.
Proceedings of the New Zealand Society of Animal Production 1994,
54: 239-242
Twelve, 10-month old ewe hoggets (Av LW 32.5 kg) were placed in
metabolism crates under controlled lighting (11 h L:13 h D) for a 9 d
adaptation period and were fed for maintenance. They were synchronized by
vaginal insertion of CIDR and treated with gonadotrophins for superovulation.
Of the 12 hoggets 9 had two or more successive plasma samples with > 0.9
ng/ml progesterone (P4) indicating they had ovarian activity prior to treatment.
Mean P4 concentrations prior to treatment (d - 3) were 0.69 ± 0.18 ng/ml and
had risen to 1.50 (± 0.38), 1.72 (±0.35), 1.36 (±0.11) and 1.31 (±0.10) ng/ml
for d 0 to d 3 of treatment. On d 9, 10 and 11, prior to CIDR removal, P4 levels
were back to base line levels (0.60, 0.46 and 0.57 (±0.06) ng/ml respectively).
The mean number of follicles and corpora lutea were 5.0 (±0.95) and 1.8
(±0.53), respectively. Total CL had a negative correlation (r = -0.64, P<0.05)
with the P4 concentration on the day of CIDR removal. Six of the 12 ewes had
an LH peak within 25 hours after CIDR removal. In addition, those ewes
treated during late cycle tended (P>0.10) to have a better ovarian response than
those treated at early or mid cycle. These results suggest it may be necessary
to use two CIDR to maintain a sufficiently long period of P4 elevation. In
addition, the day of the cycle that the CIDR is inserted may be important to
achieve maximum response from ovulation enhancement treatment in ewe
hoggets.
Keywords: NZSAPAB;
Ewe lamb; LH; Progesterone; Ovarian response; CIDR; sheep; multiple
ovulation.
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Last Updated 25-01-1997
