Evidence from the oestrous cycle for male-induced ovulation in Bettongia penicillata (Marsupialia).

Female brush-tailed bettongs (Bettongia penicillata) housed in a breeding group of one male and one to three females had an average gestation period of 21.2 days (n = 58) and parturition was followed within 24 h by oestrus and mating. If a young was not born as a result of the mating, oestrus recurred after about 21.7 days (n = 12). From removal of pouch young to birth was 17.5 days, on average (n = 85), in females that had mated post partum, but most females that were isolated from a male before parturition returned to oestrus about 6.6 days after simultaneous removal of pouch young and return to the male (n = 9). Females housed in female-only groups appeared not to come into oestrus or to do so irregularly. These females, when returned to the male, usually came into oestrus within 10 days. These data provide evidence that, in most females of B. penicillata, ovulation does not occur in the absence of a male and that previously isolated females return to oestrus within 10 days of return to the male.     

Studies of the oestrous cycle, oestrus and pregnancy in the koala (Phascolarctos cinereus)

As an integral part of the development of an artificial insemination programme in the captive koala, female reproductive physiology and behaviour were studied. The oestrous cycle in non-mated and mated koalas was characterized by means of behavioural oestrus, morphology of external genitalia and changes in the peripheral plasma concentrations of oestradiol and progestogen. The mean (+/- SEM) duration of the non-mated oestrous cycle and duration of oestrus in 12 koalas was 32.9 +/- 1.1 (n = 22) and 10.3 +/- 0.9 (n = 24) days, respectively. Although the commencement of oestrous behaviour was associated with increasing or high concentrations of oestradiol, there were no consistent changes in the morphology or appearance of the clitoris, pericloacal region, pouch or mammary teats that could be used to characterize the non-mated cycle. As progestogen concentrations remained at basal values throughout the interoestrous period, non-mated cycles were considered non-luteal and presumed anovulatory. After mating of the 12 koalas, six females gave birth with a mean (+/- SEM) gestation of 34.8 +/- 0.3 days, whereas the remaining six non-parturient females returned to oestrus 49.5 +/- 1. 0 days later. After mating, oestrous behaviour ceased and the progestogen profile showed a significant increase in both pregnant and non-parturient females, indicating that a luteal phase had been induced by the physical act of mating. Progestogen concentrations throughout the luteal phase of the pregnant females were significantly higher than those of non-parturient females. Parturition was associated with a decreasing concentration of progestogen, which was increased above that of basal concentrations until 7 days post partum.     

Characteristics of the oestrous cycle and influence of social factors in grey short-tailed opossums (Monodelphis domestica)

Characteristics of the oestrous cycle of grey short-tailed opossums were studied by vaginal smears. The period of oestrus was identified by a sudden proliferation of epithelial cells which lasted about 6 days (range 3-12 days), followed by a leucocytic infiltration. Oestrous cycle length showed a bimodal distribution of 14.4 days (5 cycles, range 11-17 days) and 32.3 days (10 cycles, range 28-39 days). Females housed with males showed more days of epithelial cell proliferation than did females housed alone, and oestrous periods tended to occur in synchrony, suggesting that social factors may influence the oestrous cycle in this species.     

Long-term effects of accelerated or delayed sexual maturation on reproductive output in wild female house mice (Mus musculus)

The effects of acceleration and delay of puberty in female house mice on survival and reproduction were tested using 6 experimental groups: (1) control females mated at the time of first oestrus, (2) females mated at weaning, (3) females treated with male urine starting at weaning and mated at first oestrus, (4) females housed in groups and mated at first oestrus, (5) females housed alone, treated with urine from grouped females and mated at first oestrus, and (6) females housed alone and mated at 68 days of age. Females caged with males at weaning or treated with male urine and mated at puberty had lower rates of survival to 180 days of age, but did not differ in rates of fertility from mice in the other four treatments. Those females that were housed with males from weaning or treated with male urine also had smaller total numbers of litters, fewer total young, and smaller average litter sizes than did females for which the age of mating was delayed, by grouping or treatment with urine from grouped females, or by being held until age 68 days before mating. Control females mated at first oestrus generally were intermediate or did not differ from the male treatments on these dependent variables. There were no differences in the average number of female young/litter across the 6 treatments. However, females that were delayed in age of first mating had significantly more male young/litter than did females that were accelerated in their sexual development or control females.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evidence from plasma progesterone concentrations for male-induced ovulation in the brush-tailed bettong, Bettongia penicillata.

Female brush-tailed bettongs, Bettongia penicillata, were housed with either an intact or vasectomized male or isolated from males in the peripartum period. Development of the quiescent corpus luteum formed at the post partum oestrus was initiated by removing the pouch young. Blood samples for analysis of plasma progesterone were collected from the females 2 days before removal of pouch young, daily for 5 or 6 days and then 2-3 times each week until 19 days after removal of pouch young. Plasma progesterone profiles were similar in pregnant and nonpregnant cycles. There was an early progesterone peak (1206 +/- 121 pg ml-1, mean +/- SEM; n = 16) between days 2 and 5 after removal of pouch young, and a second period of high concentrations (greater than 800 pg ml-1) before birth on day 17.4 +/- 0.2 (n = 16). The interval between the early peak and birth was 14 or 15 days. On five of 34 occasions, no increases in plasma progesterone concentrations occurred after removal of pouch young. On 12 of 15 occasions for 13 females that had been isolated from males post partum, plasma progesterone concentrations also remained low (less than 100 pg ml-1) and did not change after removal of pouch young. Females that showed no increases in plasma progesterone concentration after removal of pouch young had significantly lower (P less than 0.001) plasma progesterone concentrations while lactating than those females that did undergo a cycle after removal of pouch young (60 +/- 4 pg ml-1, n = 17 and 225 +/- 23 pg ml-1, n = 30, respectively). Females isolated from males post partum, and monitored until day 12 after removal of the pouch young, and that showed no increases in progesterone in this period, had ovaries that contained no corpus luteum, only corpora albicantia and numerous atretic or developing follicles. We conclude that brush-tailed bettongs are induced ovulators, a characteristic described for only one other marsupial, Monodelphis domestica, from South America.     

Changes in plasma progesterone and prolactin concentrations during the annual cycle and the role of prolactin in the maintenance of lactation and luteal development in the Antarctic fur seal (Arctocephalus gazella)

Progesterone in Antarctic fur seals was undetectable from 1-2 days before parturition to 4-6 days after parturition. There was a rapid increase in progesterone to 20 ng/ml between 6 and 10 days post partum and this increase coincided with peak concentrations of oestradiol-17 beta at the time normally associated with oestrus and mating in this species. Newly formed corpora lutea were present in the ovaries by Day 9 post partum even though the seals had been isolated in an enclosure and not mated. Thereafter, progesterone remained detectable, but at a low concentration (5 ng/ml) throughout embryonic diapause. A similar pattern was observed in unmated females which suggests they enter a period of pseudopregnancy. Progesterone increased to 35 ng/ml between late February and mid-March, indicating activation of the corpus luteum at the end of diapause, and then declined slowly through the remainder of gestation. Plasma prolactin, measured against a human prolactin standard, was elevated from 1-2 days before parturition and peaked at 0-3 days post partum. It then declined slowly throughout the post-partum period and remained at a low level throughout embryonic diapause. Prolactin concentration declined to undetectable at the end of diapause and before the end of lactation. Reduction of prolactin secretion by injections of bromocriptine from Days 3 to 5 post-partum terminated lactation. Mothers, which normally leave their pups to feed at sea on about Day 7 post partum, did not continue to lactate beyond Day 7 although this did not appear to be associated with reduced prolactin secretion. Bromocriptine treatment appeared to prevent the post-ovulatory surge of progesterone although there was no long-term effect of bromocriptine on progesterone secretion during the early stages of embryonic diapause/pseudopregnancy. This study has shown that prolactin is an important hormone for maintaining early lactation in the fur seal and it probably also has a role in the control of ovulation and luteal development. Prolactin does not appear to be implicated in the control of lactation cycles in fur seals. Changes in plasma progesterone during the annual cycle show that the pattern in fur seals resembles that of some carnivores with embryonic diapause.     

Development of dominant follicles and length of ovarian cycles in post-partum dairy cows

The resumption of ovarian activity after normal calvings was studied in 18 lactating Friesian cows. Since, in 17 cows, first post-partum ovulation occurred without overt oestrous behaviour being detected, the resultant cycles were called 'ovarian cycles'. The mean (+/- s.d.) length of the ovarian cycles was 21.0 +/- 8.7 days. The duration of cycles tended to be normal (18-24 days) or long (greater than or equal to 25 days) when the ovulatory dominant follicles were identified before Day 10 post partum; they were consistently short (9-13 days) when dominant follicles identified after Day 20 post partum ovulated. When such follicles were detected between Days 10 and 20 post partum, long, normal and short ovarian cycles were detected. The number of waves of follicular growth with associated dominant follicles observed during the ovarian cycles tended to be related to cycle length; short cycles had 1 dominant follicle, normal cycles predominantly 2, and long cycles mostly 3 dominant follicles. The mean (+/- s.d.) duration of 13 oestrous cycles studied was 23.1 +/- 2.1 days. Of these cycles, 7 had 3 and 6 had 2 dominant follicles. The oestrous cycles with 3 dominant follicles had a mean (+/- s.d.) duration of 24.0 +/- 1.2 days and the respective dominant non-ovulatory follicles reached maximum sizes on Days 8 and 18, respectively; oestrous cycles with 2 dominant follicles were 22.2 +/- 2.6 days in duration, and the dominant non-ovulatory follicle reached maximum size by Day 8. Ovarian follicular development during the first 45 days of pregnancy was characterized by the growth and regression of successive dominant follicles, each lasting 10-12 days. These results show that the first ovarian cycle was predominantly short when the ovulatory dominant follicle was first detected after Day 20 post partum.     

Social environment and reproduction in female pouched mice, Saccostomus campestris

Pouched mice were kept under controlled conditions of illumination (10D:14L) and temperature (22 +/- 2 degrees C). Age at vaginal opening, first oestrus and first conception did not differ significantly between juvenile females raised singly, in single-sex groups of 5, or with an adult male. After the introduction of a male, sterile cycles and/or matings before first conception were experienced by all females whether they were raised singly or in single-sex groups. Of 10 females raised with a male, 4 conceived at their first mating. Onset of puberty in juvenile females raised with an adult female was delayed, while in juvenile females raised with their families (mother, father and litter mates) only vaginal opening was delayed. However, when raised in family groups without the father, vaginal opening as well as first oestrus were delayed. Grouping of females after weaning, with or without a male, did not change the oestrous cycle pattern. Females in these groups cycled independently of each other and the females grouped with a male also mated and conceived independently of each other. Pregnancy was blocked in 7 of 8 females when the stud male was removed and a strange male was introduced. In females exposed to a succession of males, pregnancy was blocked up to 4 times.     

Mating post partum, concurrent lactation and reproduction in the laboratory rat.

32 of 35 sexually mature CFHB rats paired with proven males and thereafter allowed to mate post partum and nurse young concurrent with pregnancy, produced a total of 227 litters. The proportion of females producing litters decreased both with increasing age and parity, and with the number of young nursed. Litter size declined both as age and parity increased, and when gestation was extremely prolonged. The incidence and extent of delayed implantation (gestations greater than 25 days) were affected by the number of young nursed but not by increasing age and parity. There was no evidence for the existence of implantation periods coinciding with multiples of oestrous cycles.     

Effect on oestrus and ovulation of exposing creole goats to the male at three times of the year

The characteristics of the oestrous and ovarian cycles of local goats were studied over 2 years, on 96 females in March, 60 in July and 100 in November. After 3 weeks of separation between sexes, the females with inactive ovaries were identified and harnessed males were introduced. Detection of oestrus was undertaken daily and the date and rate of ovulation were checked at laparoscopies. The proportion of females with non-cyclic ovaries before the mating period varied according to the season and whether the females were nulliparous or suckling. Among the females with inactive ovaries before the mating period, 97% ovulated 2 . 8 days after the introduction of males; 68% of these initial ovulations were accompanied by oestrus and 76% resulted in short luteal phases (5 . 3 days) followed by a second ovulation accompanied by oestrus 89% of the time. The proportions of initial ovulations with oestrus and of initial ovulations followed by a short luteal phase were in linear relationship with the proportion of females with non-cyclic ovaries before the mating period. For the females with cyclic ovaries before the mating period, the distribution of first oestrus during the 8 days after the introduction of males was significantly different from the expected uniform distribution. A possible luteolytic action of teasing was suspected. The fertility of females in all groups was high (greater than 79%). Litter size was not different for non-cyclic and for cyclic females.     

Fertility, ovulation and maturation of eggs in mares injected with HCG

Pony mares were observed from January to August for incidence of oestrus, duration of oestrus, length of the oestrous cycle and for ovulation and fertility after injection of HCG. From January to 15 May most mares showed oestrus but the duration of oestrus was quite variable and few mares ovulated in response to HCG. From 15 May to 17 August oestrous cycles were more regular and ovulation was induced within 40-50 h by an intramuscular injection of 1500-5000 i.u. HCG. Pregnancy was established by one mating at a fixed time after HCG in 20 of 69 mares. Degenerate eggs were recovered from the oviducts of anoestrous recently ovulated, mated, unmated and pregnant mares. The first polar body was formed before ovulation in 2 eggs and had not formed in 2 recently ovulated eggs flushed from the oviduct. The second polar body formed after sperm penetration 10-12 h after ovulation. After formation of pronuclei, the first cleavage division occurred at 20 h and the second at 32 h after ovulation. Oestrus was inhibited by progesterone administered by vaginal devices but occurred within 1-3 days in 12 of the 20 mares after withdrawal of the devices.     

Response of cyclic and post-partum suckled cows to injections of synthetic LH-RH.

Doses of 125, 250 or 500 micrograms LH-RH were injected i.m. into suckled beef cows on approximately Day 11 of an oestrous cycle synchronized by prostaglandin treatment. There was a positive linear relationship between dose of LH-RH and the area under the measured LH peak. Administration of 500 micrograms LH-RH as a single injection to suckled cows 13-32 days post partum resulted in LH release but failed to induce normal ovarian activity. A small transient rise in plasma progesterone for 6--9 days occurred at the expected time after injection in 50% of animals. Administration of 500 micrograms LH-RH to suckled beef cows approximately 20--30 days post partum and a second injection approximately 10 days later at the time when the resulting transient rise in plasma progesterone had returned to basal values induced normal cyclic activity (as shown by progesterone concentrations and observed oestrus) at 35 days compared with 70 days for untreated controls. Pituitary responsiveness to LH-RH, as assessed by LH levels, was found to increase up to 20 days post partum.     

Reproductive biology of the Red-necked wallaby (Macropus rufogriseus banksianus) and Bennett's wallaby (M. r. rufogriseus) in captivity

Bennett's wallaby ( Macropus r. rufogriseus ) of Tasmania give birth from late January to early August in marked contrast to the Red-necked wallaby ( M. r. banksianus ) of mainland south-eastern Australia which produced young in all months. Within the breeding season however, the lengths of the oestrous cycle and gestation period are similar in the two forms and did not differ by more than 0.5 days. The gestation period of about 30 days extended to almost the length of the oestrous cycle of approximately 33 days. Birth was closely followed by mating which normally resulted in fertilization and subsequent embryonic diapause. Renewed blastocyst development was initiated by removal or loss of a pouch young and birth followed about 27 days later.
Unlike other macropodids with a similar breeding pattern, birth, as a result of renewed blastocyst development near the end of a large young's pouch life, did not occur within a day or two of the permanent emergence of the young, but followed 16 to 29 days later. In M. r. rufogriseus , young that left the pouch permanently in the non-breeding period were not replaced by new young until the beginning of the next breeding season two to four months later, and blastocysts resulting from mating of females without pouch young at the end of the breeding season remained quiescent until the next breeding season five to eight months later.
Females of both subspecies first mated at an age of about 14 months, and males were producing mature spermatozoa by about 19 months.
Young first left the pouch for short periods at about 230 days of age and permanently at about 280 days.
Observations are also given on reproductive behaviour, interpretation of vaginal smears, sex ratio of young, selection of teat by pouch young, and development of morphological features in known-age young that may be used as an aid in age determination.     

Some physiological and behavioural changes associated with oestrus and pregnancy in the squirrel monkey (Satmiri sciureus)

Peak values in the karyopyknotic index of vaginal smears from the squirrel monkey occurred at intervals of 10.9±0.1 days. The urinary excretory rate of a metabolite similar to preg-nanediol increased when ovulation was induced by exogenous gonadotropin therapy. Small amounts of this metabolite were excreted during lactation, periods of anoestrus and during the follicular phases of normal oestrous cycles. Significantly larger amounts were excreted during the 157 days gestation period and during the luteal phase which persisted for one week after a peak karyopyknotic index value was observed. Changes in the pattern of urinary electrolyte excretion were not correlated reliably with changes in ovarian differentiation. Sexual motivation was greatest at mid-cycle, became less after conception and persisted at a low level throughout gestation and lactation. The occurrence of oestrus was seasonal and independent of physical contact with males. The development of secondary sexual characteristics in the male was synchronized with the onset of seasonal oestrus in the females.     

Postnatal development of the skin of the marsupial native cat Dasyurus hallucatus

Skin development of the Northern native cat was examined from birth to weaning at 150 days post partum. An outer layer of cells, termed the periderm or epitrichium, is present on the epidermis of the newborn. This layer of cells is not discernible at 7 days post partum. Skin development of the native cat differs from that of the eutherian mammal. The periderm of the eutherian is no longer discernible when the developing hairs first penetrate the epidermis. In the marsupial, this loss of the periderm occurs well before the appearance of follicles. Melanocytes and Langerhans cells are seen at day 23 post partum, follicles at day 30, sebaceous glands at day 59, and sweat glands at day 67. Thus, when the mother first leaves her young in the nest at about days 60 to 70 of lactation, the skin is at a stage of development that will assist the young with thermoregulation. The skin continues to develop throughout lactation and attains an adult appearance by day 150 post partum.     

Pattern of follicular growth and resumption of ovarian activity in post-partum beef suckler cows

The ovaries of 18 post-partum beef suckler cows were examined daily, using ultrasound, from Day 5 post partum until a normal oestrous cycle was completed. Periods of growth and regression of medium-sized (5-9 mm) follicles were identified before one medium follicle became dominant (single large follicle greater than or equal to 10 mm). The mean (+/- s.e.m.) number of days from parturition to detection of the first post-partum dominant follicle was 10.2 +/- 0.5. The first post-partum dominant follicle ovulated in 2/18 (11%) cows. The interval from calving to first ovulation (mean +/- s.e.m. = 35.9 +/- 3.3 days) was characterized by the growth and regression of a variable number (mean = 3.2 +/- 0.2; range 1-6) of dominant follicles. The maximum diameter of the dominant follicle increased as the cows approached first ovulation (P less than 0.05). Behavioural oestrus was not detected in 16/18 (89%) cows at first ovulation. Following first ovulation, the length of the subsequent cycle was short (mean = 9.7 +/- 0.5 days; range 8-15 days) in 14/18 (78%) cows and was characterized by the development and ovulation of a single dominant follicle. During oestrous cycles of normal length (mean = 20.6 +/- 0.5 days; range 18-23 days) one (N = 2), two (N = 7) or three (N = 8) dominant follicles were identified. The growth rate, maximum diameter or persistence of non-ovulatory dominant follicles before first ovulation or during oestrous cycles were not different (P greater than 0.05). These data show that, in beef suckler cows, follicular development and formation of a dominant follicle occur early after parturition and the incidence of ovulation of the first dominant follicle is low. The number of dominant follicles that develop before first ovulation is variable; first ovulation is rarely associated with oestrus and short cycles are common after first ovulation. It is concluded that prolonged anoestrus in post-partum beef suckler cows is due to lack of ovulation of a dominant follicle rather than delayed development of dominant follicles.     

Oestrous cycle and breeding season of farmed fallow deer, Dama dama

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.     

Behavioural aspects of the raccoon mating system: determinants of consortship success

We monitored raccoons Procyon lotor, in southern Texas during the 1990-1992 mating seasons to describe mating behaviour and identify factors affecting consortship success. During most of this study, raccoons were spatially aggregated, with female home ranges congregated around permanent water sources and larger home ranges of male groups encompassing each female group. Consortship success varied among males and ranged from zero to six females per male within a mating season. Individual females consorted with one to four different males during an oestrous period; however, most (62%) females consorted with only one male during their oestrus. Dominance through overt conflict appeared to influence male consortship success. During two mating seasons, one male from each group consorted with females on more days than all other males combined. Body weight of males was positively correlated with number of consortship days. As synchrony of oestrus increased, variance in number of consortship days among males decreased, and access to oestrous females increased for subordinate males. Wounding among males increased during the mating season, and was more frequent for males than for females. The mating system, as determined by consortship behaviour, appeared to shift between polygyny and promiscuity, and possibly varied annually as a result of the timing of oestrous cycles. Copyright 1999 The Association for the Study of Animal Behaviour.     

Post partum ovarian activity and uterine involution in the suckled swamp buffalo (Bubalus bubalis)

Ovarian activity and uterine involution were monitored by rectal palpation, oestrus detection and plasma progesterone analysis from 3 to 4 days to approximately 150 days post partum in 38 suckled swamp buffaloes (Bubalus bubalis). The intervals from parturition to regression of the corpus luteum (CL) of pregnancy and involution of the uterus were 10 and 28 ± 6 (S.D.) days respectively. First detected oestrus and first elevation of plasma progesterone (> 0.7 ng/ml) occurred at 88 ± 26 and 96 ± 22 days in 8 and 12 buffaloes respectively. During the first 150 days post partum, 26 of 38 suckling buffaloes (68%) were acyclic (anoestrus) and of 12 animals (32%) exhibiting ovarian cycles, 4 were not detected in oestrus. The tentative diagnosis, based on rectal palpation, that CL were present between days 30 and 90 after parturition (without concurrent luteal levels of progesterone in plasma) suggests that confirmation should be by laparoscopy. It is concluded that a delay in the resumption of ovarian cyclicity post partum represents an important factor contributing to the prolonged calving to conception interval in the suckled swamp buffalo.     

Reproduction in the female Angolan free-tailed bat, Tadarida (Mops) condylura (Microchiroptera: Molossidae), in the eastern Transvaal, South Africa

The reproductive pattern in the female Angolan free-tailed bat, Tadarida (Mops) condylura (A. Smith, 1833), was studied at two localities in the eastern Transvaal during the period 1988–1990. Reproduction in female T. condylura was seasonally polyoestrous. Females displayed a bimodal reproductive pattern, with reproductive activity extending from early September to early May, followed by reproductive quiescence from May to August. The interval between the two reproductive cycles was marked by a post-partum oestrus with adult females becoming pregnant one to three weeks after parturition while still nursing their young. Females become sexually mature during their first year with some only undergoing one pregnancy. Gestation and lactation periods were 85 days and 50–60 days, respectively. Females displayed dextral dominance with regard to the morphology and function of the ovary and uterus.