The influence of reproductive status on pituitary gland function
in seasonally anoestrous red deer hinds
M.W. FISHER, B.J. MCLEOD, L.M. MEIKLE, S.K. MARTIN
AgResearch Invermay Agricultural Centre, Private Bag 50034,
Mosgiel, New Zealand
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Proceedings of the New Zealand Society of Animal Production 2001. 61:
141-143
Changes in pituitary responsiveness to exogenous hypothalamic
hormones were assessed during seasonal anoestrous in dry, preGnant and
lactating hinds. Of the fifteen adult red deer hinds monitored, five
were non-pregnant, five had their calves removed immediately after
birth, and five suckled their calves. All hinds were given a single i.v.
injection of hypothalamic releasing hormones (5µg each of GnRH, GRF
and TRH) on four occasions between Nov/Dec (10 days prior to calving)
and March. The pituitary response was determined from changes in plasma
concentrations of LH, growth hormone, and prolactin in samples obtained
by jugular venepuncture at 0, 15 and 30 min after injection.
Reproductive state significantly (P<0.001) affected LH release with a
mean response (over all sample dates) of 1.12 ng/ml in dry hinds
compared with 0.85 ng/ml in hinds that had their calves removed and 0.60
ng/ml in lactating hinds. Neither growth hormone (average 5.65 ng/ml)
nor prolactin (average 33.9 ng/ml) responses were affected by
reproductive status.
Keywords: NZSAPAB;
red deer hind; pituitary; hypothalamus; LH; prolactin; growth
hormone
Last Updated 7/08/01
