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G. W. Asher

Summary. Oestrus was detected on 177 occasions in 34 fallow does for the duration of the breeding season. A total of 142 cycles had a mean length of 22·4 (± 1·3, s.d.) days. Cycle length increased and became more variable as the season proceeded but was not affected by doe age or liveweight. First oestrus occurred within a 12-day period, but the length of the breeding season, and therefore the number of oestrous cycles, was related to doe age. Serum progesterone profiles suggest that silent ovulations, associated with short-lived corpora lutea, occurred before the first behavioural oestrus. Ovulations without oestrus may have also occurred at the end of the breeding season.

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G. W. Asher and A. J. Peterson

Summary. Pituitary secretion of LH and testicular secretion of testosterone were investigated during the transitional period from the non-breeding to breeding season of mature male fallow deer exhibiting either normal transitional patterns or shortened transitional patterns in response to summer melatonin treatment. Melatonin implants were administered to 4 bucks for a 150-day period starting 130 days after the winter solstice. Four contemporary bucks served as controls. Melatonin treatment advanced rutting activity, testis development and neck muscle hypertrophy by 6–8 weeks. Profiles of plasma LH and testosterone, based on a 30-min sampling frequency over 24 h, were obtained from 3 treated and 3 control bucks on 4 occasions over the period spanning the transition into the breeding season. In control bucks, LH and testosterone pulse frequency were low (0–2 pulses/24 h) in January and increased (5–7 pulses/24 h) in February. By March and April (pre-rut and rut periods respectively) there was a two-fold increase in basal plasma LH concentrations, a decline in LH pulse frequency (0–1 pulse/24 h) and episodic surges in plasma testosterone concentrations. Melatonin treatment resulted in a shift in hormone profiles, with highly pulsatile patterns of LH and testosterone secretion (7 pulses/24 h) occurring earlier in January. The subsequent post-rut profiles of treated bucks were characterized by lower basal plasma LH concentrations, and reduced frequency and amplitude of plasma testosterone surges.

Keywords: fallow deer; reproduction; melatonin; LH; testosterone; testis

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G. W. Asher and K. L. Macmillan

Summary. Fourteen seasonally anoestrous, non-lactating fallow does were each treated with an intravaginal progesterone device for 14 days followed by a subcutaneously implanted osmotic minipump delivering synthetic GnRH at doses of 125 ng/h (7 does) or 250 ng/h (7 does) for up to 7 days, about 6 weeks before the natural breeding season. One doe (low delivery rate) lost its intravaginal device and 6 of the remaining does (46·2%) exhibited oestrus between 71 and 120 h after progesterone withdrawal/minipump insertion. Only one of these does received the low GnRH delivery rate and 5 received the high rate. Serum progesterone profiles indicated that an induced oestrus was followed by apparently normal luteal development. Does which did not exhibit oestrus failed to show a luteal response. Only 1 doe conceived at induced oestrus, producing a viable female fawn 6 weeks before the start of the natural fawning season. The remaining does returned to an anoestrous state until the onset of the natural breeding season.

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G. W. Asher and J. F. Smith

Summary. Twenty non-lactating fallow does were each treated with an intravaginal progesterone device (CIDR) for 14 days followed by an i.m. injection of 500 i.u. PMSG, 3–4 weeks before the expected start of the natural rut. An additional 7 does received no treatments and were used as controls. Induced oestrus was observed for 19 (95%) of the treated does, the onset occurring between 48 and 76 h after CIDR removal/PMSG administration. Laparoscopic examination 12 days after CIDR removal revealed ovulation rates ranging from 1 to 4 in treated does. Non-ovulating luteinized follicles were also a feature of PMSG treatment and there was a significant inverse relationship between ovulation rate and numbers of luteinized follicles. Only 3 (14·3%) of the treated does conceived at or near the induced oestrus, the remainder returning to oestrus 21–27 days later. Mid-cycle progesterone concentrations were positively related to ovulation rate. All control does showed evidence of a recent single ovulation at laparoscopy, although first oestrus did not occur until 7–15 days later, indicating the occurrence of silent ovulations before the natural breeding season.

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G. W. Asher, A. J. Peterson and W. B. Watkins

Summary. Concentrations of progesterone, oxytocin and PGFM (pulmonary metabolite of PGF-2α) were measured in plasma from peripheral blood samples collected from 5 fallow does every hour or 2 h for 12-h periods on Days 15–20 inclusive of the oestrous cycle (i.e. luteolysis). For 3 does that exhibited oestrus on Day 21, plasma progesterone concentrations fluctuated between 3 and 10 ng/ml on Days 15–18 inclusive. Thereafter, values declined progressively to attain minimum concentrations of <0·5 ng/ml on Day 20. Basal concentrations of plasma oxytocin and PGFM fluctuated between 5 and 20 pg/ml and 10 and 100 pg/ml respectively. Episodic pulses of plasma oxytocin (>300 pg/ml) occurred on Days 15 and 16, whereas pulses of plasma PGFM (>400 pg/ml) occurred on Days 19 and 20. There was little apparent correlation between episodic pulses of the two hormones. For 2 does that exhibited oestrus on Day 22, plasma progesterone concentrations declined to minimum values of 1·0–1·5 ng/ml by Day 20. One of these does showed very high levels of oxytocin secretion throughout the sampling period while the other showed an apparent paucity of oxytocin secretory periods. Two does hysterectomized on Day 13 of their second oestrous cycle failed to exhibit further oestrous cycles. Continual elevation of plasma progesterone concentrations (2–6 ng/ml) for an 8-month period indicated persistence of the corpus luteum after hysterectomy. It is concluded that luteolysis in fallow deer involves episodic secretion of both oxytocin and PGF-2α.

Keywords: fallow deer; Dama dama; reproduction; luteolysis; prostaglandin; oxytocin

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G. W. Asher, A. M. Day and G. K. Barrell

Summary. Entire bucks (N = 7) exhibited pronounced liveweight gains over spring and summer months (October–February), to reach a peak mean weight of 59·8 kg, and rapid liveweight losses over the rutting period (April–May) with a minimum mean liveweight of 54·2 kg. Mean neck girth and serum testosterone levels increased during late summer (January–March) and peaked at 387 mm and 12 ng/ml respectively immediately before the onset of the rut (April). Thereafter both measures declined during winter and spring months (June–December). Bucks castrated prepubertally (N = 11) exhibited similar but less pronounced changes in mean liveweight and neck girth, in the absence of any change in testosterone secretion. Peak mean testicular diameter of entire bucks (39 mm) occurred immediately before the rut and was followed by testicular regression over winter and spring months (June–November), such that the testes attained their minimum mean size of 18 mm diameter in early summer (November). Motile spermatozoa were absent from ejaculates collected in summer (November 1983, 1984; January 1984). However, ejaculates collected pre-rut (late March), immediately post-rut (June) and in early spring (September) contained successively increasing numbers of motile spermatozoa.

A further 14 polled, entire bucks were given orally 5 mg (N = 7; Group A) or 20 mg (N = 7; Group B) melatonin at 15:30h daily from 1 December 1983 to 14 January 1984 (45 days). Seven control bucks (Group C) received vehicle ration only. The measurements taken for bucks in Groups A and B were not significantly different (P > 0·1) on any sampling date and the data for these 2 groups were pooled. Mean serum testosterone concentrations and mean ejaculate volume were not significantly different between melatonin-treated and control bucks on any sampling date, although other measures exhibited significant differences (P < 0·05) at various treatment or post-treatment dates: melatonin-treated bucks showed a transiently greater increase in neck muscle development during and immediately after treatment, a slight retardation of liveweight gain between 45 and 75 days after treatment, an earlier peak in maximum mean testicular diameter and an earlier onset of sperm presence in ejaculates.

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G. W. Asher, G. K. Barrell and A. J. Peterson

Summary. Concentrations of LH, progesterone, oestradiol-17β and androstenedione were measured in serum from blood samples collected from 6 fallow does every hour for 46 h during a spontaneous oestrus. Four does had similar serum hormone profiles, with a pronounced preovulatory LH surge (∼ 20 ng/ml) occurring within 4 h of the onset of oestrus, a small elevation (from 0·1 to 0·3 ng/ml) of progesterone at the onset of oestrus, a gradual but non-significant increase (up to 25 pg/ml) of oestradiol-17β and a marked 2-fold increase of serum androstenedione concentrations occurring immediately at the onset of oestrus. The remaining 2 does showed pronounced increases in serum progesterone concentrations at the onset of oestrus and a reduction in the initial LH surge. One of these does exhibited a second preovulatory LH surge within the sampling period.

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G. W. Asher, A. J. Peterson and D. Duganzich

Summary. Six young female fallow deer, including 3 that were ovariectomized at 9 months of age, were blood sampled at frequent intervals after i.v. injections of (1) ACTH analogue (tetracosactrin), (2) GnRH analogue (buserelin) and (3) saline solution on separate occasions at 11, 13, 15 and 18 months of age. Relative to prechallenge plasma values, ACTH administration resulted in a 4–10-fold increase in mean plasma progesterone concentrations, but only a 10–45% increase in mean plasma cortisol concentrations, within 40 min for entire and ovariectomized does during the prepubertal periods (11, 13 and 15 months) and for ovariectomized does during the post-pubertal period (18 months). Post-pubertal entire does exhibited high mean basal plasma progesterone concentrations (3–4 ng/ml) indicating a luteal source of secretion, with the ACTH-induced progesterone response being additive to the luteal progesterone but of similar magnitude to responses in the ovariectomized does. There was no significant ACTH challenge effect on mean plasma LH concentrations for entire or ovariectomized does at all ages.

GnRH administration had no significant effects on mean plasma concentrations of progesterone and cortisol of entire and ovariectomized does, although there was a small increase in mean plasma progesterone values in post-pubertal does that may have reflected a luteal response to GnRH (via LH). GnRH challenge resulted in marked increases in mean plasma LH concentrations but the response patterns were different for the 2 types of does, being more rapid and of higher magnitude for ovariectomized does.

Saline injections had no significant effects on mean plasma hormone concentrations for entire and ovariectomized does at any age.

It is concluded that the adrenal glands are secondary and major sources of progesterone in fallow deer and that there exists a two-phase response of adrenal glands to stress/ACTH stimulation in terms of cortisol and progesterone secretion.

Keywords: fallow deer, progesterone, cortisol; adrenal gland; corpus luteum

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G. W. Asher, A. J. Peterson and J. J. Bass

Summary. At monthly intervals during the year blood samples were collected every 20 min for 12 h from 4 entire and 2 prepubertally castrated adult fallow deer bucks. In the entire bucks there were seasonal changes in mean concentrations and pulse frequencies of plasma LH. Mean concentrations in late summer and autumn were 3–6 times higher than during other seasons. LH pulse frequency was low (0–1 pulses/12 h) during most of the year and increased only during the 2-month period (January and February) that marked the transition from the non-breeding season to the autumn rut. During this period there was a close temporal relationship between pulses of LH and testosterone. However, during the rutting period (March and April) episodic secretion of testosterone, manifest as surges in plasma concentrations of 4–6 h duration, was not associated with any detectable pulses in LH although mean plasma concentrations of LH remained elevated. During the rut, the surges of plasma testosterone occurred at similar times of the day. Plasma profiles in May indicated very low concentrations of LH and testosterone secretion in the immediate post-rut period. Castrated bucks exhibited highly seasonal patterns of LH secretion, with mean plasma LH concentrations and LH pulse frequency being lowest in November (early summer) and highest in February and March (late summer–early autumn). Mean concentrations and pulse frequency of LH in castrated bucks were higher than for entire bucks at all times of the year.

Keywords: fallow deer; reproduction; pituitary; testis; LH; testosterone

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G. W. Asher, M. W. Fisher, J. F. Smith, H. N. Jabbour and C. J. Morrow

Summary. A study was conducted to determine the timing of ovulation relative to the onset of oestrus and the preovulatory LH surge in fallow deer. Mature fallow does were randomly allocated to two treatments (N = 10 per treatment) designed to synchronize oestrus on or about 17 May. Does assigned to Group 1 (prostaglandin-induced oestrus) each initially received single intravaginal CIDR [Controlled Internal Drug Release] devices for 13 days followed by an i.m. injection of 750 mg cloprostenol on Day 12(15 May) of the subsequent luteal cycle. Does assigned to Group 2 (progesterone-induced oestrus) each received CIDR devices for 13 days, with withdrawal occurring on 15 May. All does were run with crayon-harnessed bucks (10:1 ratio) from the start of synchronization (18:00 h 15 May). Ten does (5 per group) were blood sampled via indwelling jugular cannulae every 2 h for 72 h from cloprostenol injection or CIDR device withdrawal and the plasma was analysed for concentrations of progesterone and LH by radioimmunoassay. Does within each treatment were randomly allocated to an ovarian examination time of 12, 16, 20 or 24 h after the onset of oestrus. Laparoscopy was repeated at 12-h intervals until ovulation was recorded. The ovaries of does failing to exhibit oestrus were examined 72 and 86 h after cloprostenol injection or CIDR device withdrawal. A total of 17 does were observed to exhibit oestrus at a mean (±s.e.m.) interval from treatment of 44·6 ± 3·6 h for Group 1 (N = 9) and 34·1 ± 2·5 h for Group 2 (N = 8). The incidence of ovulation from 34 laparoscopic examinations was 0% for intervals <20 h, 50% at 24 h and 100% for intervals >28 h. There was no difference between animals in Groups 1 and 2. The onset of the preovulatory LH surge (n = 8 observations) occurred at the onset of oestrus, with maximum LH surge concentrations (30 ng/ml) occurring 6 h later. Of 3 does not exhibiting oestrus, 2 (Group 2) possessed active corpora lutea at CIDR device withdrawal and 1 (Group 1) possessed a large unruptured follicle 72 and 86 h after cloprostenol injection.

The data indicate that ovulation in fallow deer occurs ∼24 h after the onset of oestrus and ∼ 18 h after the peak of the preovulatory LH surge.

Keywords: fallow deer; reproduction; oestrus; ovulation; progesterone; LH