Exogenous progesterone and oestradiol benzoate (OB) were used in long-term ovariectomised red deer to investigate a simple technique for induction of oestrus. Up to 12 days of intravaginal progesterone (CIDR-S; replaced at 4 day intervals) was followed 24h later by a single intramuscular injection of OB. Continual observations (for behavioural oestrus) and blood sampling every 6h (for plasma LH concentrations) were conducted over the subsequent 48h period. In Experiment 1 (December), 12 days of progesterone preceded 0, 1.0, 2.5 or 5.0 mg OB. Onset of oestrus (28-44h post-OB; mean 33h) was similar in all treated hinds. Plasma LH concentrations fell (P<0.01) after OB administration, followed 30 to 36h later by a dramatic increase (to 6.4 ng/ml) indicative of pre-ovulatory-like LH surge. Hinds receiving no OB exhibited 4% of all mounting interactions but showed no increases in LH concentration. Experiment 2 (January) consisted of no treatments or 12 days or progesterone followed by 0, 0.1 or 1 mg OB resulted in suppression of plasma LH after OB. However, all other plasma LH and behaviour responses elicited were anomalous. In Experiment 3 (February), 0,4, 8, or 12 days of progesterone pretreatment were terminated 24 hours prior to administration of 1 mg OB. Plasma progesterone concentrations were elevated above 1 ng/ml during all progesterone treatments. Onset of oestrus was observed later (P<0.5) after 4 days of progesterone treatment (33.4h; sem 1.2h). Tonic plasma LH secretion was elevated (P<0.01) from Experiment 1 through to Experiment 3 but the plasma LH suppression in response to OB was similar in all 3 experiments. These results indicate that oestrus can be induced in the red deer hind by at least four days of intravaginal progesterone treatment followed by i.m. oestradiol benzoate administration 24h after progesterone removal.

AY, Abdullah, RW Purchas, SN McCutcheon, and PC Van Dinther

Proceedings of the New Zealand Society of Animal Production, Volume 50, , 105-108, 1990
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