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Monitoring ovarian function and pregnancy in Eld's deer (Cervus eldi thamin) by evaluating urinary steroid metabolite excretion

Summary. Direct radioimmunoassays (RIA) for urinary oestrone conjugates and pregnanediol-3-glucuronide (PdG) were used to study ovarian activity patterns and pregnancy in Eld's deer. In 2 does, urinary metabolite patterns were compared to temporal patterns of plasma LH, oestradiol-17β and progesterone. Preovulatory LH peaks occurred coincident with behavioural oestrus, and plasma progesterone secretion paralleled PdG excretion. Although plasma oestradiol-17β levels fluctuated between 5 and 10 µg/ml throughout the oestrous cycle, no preovulatory oestrogen surge was observed. Based on PdG excretion, non-conception oestrous cycles averaged 21·5 ± 2·1 days (±s.e.m., n = 65); however, 2 of 13 does exhibited prolonged oestrous cycles (30·1 ± 4·4 days; range 14–62 days, n = 14) characterized by sustained PdG excretion. Excluding these 2 females, the mean oestrous cycle was 18·5 ± 0·3 days (range 14·23 days, n = 51). Behavioural oestrus (12·24 h duration) was observed in 42 of 65 cycles (64·6%), and always corresponded with intercyclic troughs in PdG excretion (2·5 days duration). Mean gestation duration (n = 10) was 33·5 ± 0·4 weeks. PdG concentrations increased (P < 0·05) by Week –32 (3rd week of gestation), plateaued between Weeks –31 and –25, increased (P < 0·05) markedly by Week –22 and then rose steadily until parturition, declining (P < 0·05) rapidly thereafter. Mean excretion of oestrone conjugates remained low until Week –30, increased (P < 0·05) steadily to Week –24 (P < 0·05) and then returned to baseline by Week –17. Increased (P < 0·05) oestrone conjugates concentrations were detected again by Week –4 followed by a rapid increase to peak pregnancy levels by Week –1, declining (P < 0·05) precipitously after parturition. The results confirm that the Eld's deer is seasonally polyoestrous with onset (January–March) and cessation (August–October) of regular, cyclic ovarian activity coinciding with increasing and decreasing daylengths, respectively. Urinary PdG excretion accurately reflects cyclic ovarian activity and markedly elevated concentrations of this metabolite provide an accurate index of pregnancy. The simultaneous monitoring of oestrone conjugates appears useful for estimating the stage of pregnancy and predicting parturition onset.

Keywords: Eld's deer; oestrogen; progesterone; urinary steroids; LH; seasonality

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