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.     

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.     

Comparison of females treated with oestradiol or testosterone to detect oestrus in dairy cattle maintained indoors year-round

The effectiveness of three females treated with oestradiol and three females treated with testosterone to detect oestrus was examined in 304 dairy cows maintained indoors year-round. Three heifers were treated weekly with 10 mg oestradiol benzoate per 250 kg of body weight. One cow and two heifers were treated with 10 injections of testosterone propionate (200 mg) every other day and an injection of testosterone enanthate (500 mg) every 10 days thereafter. During one year, there were 858 periods of oestrus detected by herdsmen observation - using standing, mounting, mucous discharge and any combinations thereof and, or, the hormone-treated females. Of these, the herdsmen detected 94% compared with 51% by the hormone-treated females. The 6% not detected by the herdsmen were detected by the treated females only. Oestradiol-treated females detected oestrus in cows as effectively as testosterone-treated females.     

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)     

Maturation of ovarian function in female ferrets is influenced by photoperiod

Sexual maturation of immature ferrets in response to a stimulatory photoperiod generally occurs within 6-7 weeks after imposition of long days at 16 weeks of age. In this study, females were examined for evidence of ovarian maturation after 22 days of exposure to the stimulatory photoperiod, before any sign of sexual maturation. The photoperiod-stimulated and control females were the same age (19 weeks), had similar body weights, and showed no evidence of vulvar oedema. Comparison of oestradiol secretory response to hCG stimulation and of follicular development in the ovary revealed marked ovarian stimulation in females kept in long days compared to control females kept in short days. A prolonged period of ovarian stimulation therefore occurs during exposure to long days before there is external evidence of sexual maturation in ferrets.     

Cycles of mating behaviour, oestrogen and progesterone in the thick-tailed bushbaby (Galago crassicaudatus crassicaudatus) under laboratory conditions

Vaginal smears and blood samples were taken throughout the reproductive cycle of female Galago c. crassicaudatus. Blood plasma was assayed for oestradiol and progesterone, and vaginal smears were initially classified dioestrus or vaginal oestrus. During vaginal oestrus the females were tested daily for sexual receptivity by being placed with a male. Those days on which the male achieved intromission were reclassified as behavioural oestrus. During dioestrus the females were tested weekly with males. Female receptivity increased and then declined across a 6-day period of behavioural oestrus during the 44-day cycle. Fully cornified smears were characteristic of the period of maximal receptivity and oestradiol secretion. The luteal phase lasted 24 days with a plasma progesterone peak midway through dioestrus.     

Is there a critical weight for oestrus in the ferret?

Information concerning the weight at the onset of a period of oestrus, the timing of oestrus, the age at first oestrus and the lighting conditions was collected from the records of 1364 ferrets and reviewed for evidence indicating that the animals became sexually mature around a particular, critical, weight. None was found, but the results suggest that there is a minimum weight, around 420 g, below which oestrus does not occur.     

Reproductive biology and management of captive black-footed ferrets (Mustela nigripes)

A captive breeding program is being conducted with black-footed ferrets (Mustela nigripes), an endangered species. Results of 5 years of study are reported. Simple, but specialized, nontraumatic handling techniques allowed assessment of reproductive status with minimal stress, which was important in breeding management. Black-footed ferrets are sexually mature and may successfully reproduce in their 1st year. Proestrus lasts approximately 2-3 weeks. Duration of estrus in unbred females was 32–42 days; females usually bred within 20 days. Most breeding activity occurred during April. Mean gestation length was 42.7 days (±0.7, range 42–45 days), litter size averaged 3.0 kits (±1.4, range 1–6 kits), and weaned kits/litter averaged 2.4 (±1.7, range 1–6 kits). Weaning rate of kits was 80%. Sex ratio of kits was essentially 1:1. Productivity was greatest among females ?3 years of age. Rapid expansion of the captive population is possible and will be important for genetic management of the species and for achieving the primary goal of the recovery program, which is to return black-footed ferrets to the wild.     

Cytoplasmic binding of oestradiol-17beta in several brain regions, pituitary and uterus of ferrets ovariectomized while in or out of oestrus

The reproductive status at the time of ovariectomy had no effect on oestradiol binding. In both groups of ferrets the oestradiol binding capacity of the uterus was approximately 10 times greater than that of the other tissues studied; of these other tissues the highest oestradiol binding capacity was present in the pituitary, followed by hypothalamus, midbrain, amygdala and cerebral cortex. The binding affinity of hypothalamic receptors for oestradiol was the same in ferrets which had been previously ovariectomized while either in oestrus or anoestrus. It is suggested that the occurrence of seasonal oestrus does not depend on changes in the binding capacity or affinity of hypothalamic receptors for oestradiol.     

Influence of day length and endocrine status on luteinizing hormone secretion in intact and ovariectomized adult ferrets

The purpose of this study was to examine the pituitary-ovarian relationship of both estrous and anestrous female ferrets. The endocrine status of the animals was induced by manipulating photoperiod: females in estrus were housed in long days (16L:8D); females in anestrus were housed in short days (8L:16D). For studies of intact animals in both photoperiods, plasma luteinizing hormone (LH) levels were quantified in blood samples collected from adult ferrets at 5-min intervals over a 24-h period. Similar groups of females (estrous and anestrous) were ovariectomized (while remaining in their assigned photoperiods) and blood samples were collected at 5-min intervals for 4-h periods on Days 1, 2, 4, 10, 17, and 35 after ovariectomy. Intact, estrous females exhibited continuously low or undetectable levels of LH with no evidence of episodic secretion. Ovariectomy of these estrous animals resulted in rapid onset (within 24 h) of episodic LH secretion, with pulses occurring in excess of 1 pulse/h. No substantial further change in frequency or amplitude of pulses occurred in these females from 1 to 35 days postovariectomy. In contrast, intact anestrous ferrets exhibited clear episodic LH secretion at a frequency of about 0.4 pulses/h. Removal of ovaries from these females caused no change in LH secretion for 24-48 h, after which LH pulses gradually increased in frequency. By 18 days after ovariectomy, LH patterns were indistinguishable among ovariectomized females in long and short days. These studies suggest a major site of ovarian negative feedback on LH secretion during anestrus is the hypothalamus, whereas the site of the ovarian feedback in estrous females is not yet evident.     

Dracunculus insignis: experimental infection in the ferret, Mustela putorius furo

The laboratory study of dracunculiasis has suffered from the lack of a suitable, readily available animal model. We have been able to experimentally infect ferrets. Mustela putorius furo, with the North American dracunculid, Dracunculus insignis. Ferrets were inoculated with 75 to 100 infective larvae and were necropsied 90 to 240 days later. Guinea worms were recovered from 10 (56%) of 18 ferrets. A total of 44 worms were recovered, for an average of 4.4 worms per infected ferret. Gravid female worms were recovered as early as 128 days postinoculation. Thirteen (87%) of 15 gravid female worms were recovered from the extremities. Living male worms were recovered at 200 days of age, indicating that not all male worms die shortly after mating. First-stage larvae recovered from gravid females as early as 200 days of age were found to be infective to the copepod, Acanthocyclops vernalis. These observations suggest that the ferret is an excellent laboratory animal for dracunculiasis research.     

A study of spontaneous sexual maturation of the female ferret

Although ferrets are long-day breeders, females reared exclusively in nonstimulatory short days will undergo spontaneous sexual maturation by 30-50 wk of age. In the following report, this spontaneous sexual maturation of ferrets was studied to determine mechanisms regulating sexual maturation in nonstimulatory photoperiods. Study of ovariectomized females treated with low, constant levels of estradiol suggest that a marked decrease in the efficacy of estradiol to inhibit luteinizing hormone secretion occurs shortly before sexual maturity becomes evident in intact controls (both groups housed in short days). During this long juvenile period, a marked increase in body weight occurred, but ovarian responsiveness to exogenous gonadotropin did not change. Older, larger females did respond more rapidly to stimulatory photoperiod than did younger females. These studies suggest that the mechanisms of spontaneous puberty in ferrets are likely the same as those regulating photoperiod-stimulated puberty in this species.     

Reproduction in a laboratory colony of the pouched mouse, Saccostomus campestris

Pouched mice ovulate spontaneously and have a 4-day cycle (3-5 days). The variation was caused by prolonged oestrus. The vagina opened at about 34 days of age and the first oestrus was experienced at 44 days of age. Females experienced several sterile cycles before their first conception, which occurred at an age of about 56 days. The gestation period in most cases was 21 days and implantation occurred about 4-5 days after mating. The females were not receptive post partum. Litter size varied from 3 to 13 with a mean of 7.1 in young primiparous females and 7.9 in adult multiparous females, indicating that fecundity did not increase with age or parity in this species. Mortality of young was highest during the first 2 days post partum. The young were not attached to the nipples and were weaned at 25 days of age. Females did not cycle during lactation. After lactation most females exhibited one or two oestrous cycles without mating or became oestrous and mated without conceiving, resulting in a litter interval of about 53 days.     

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.     

Spatial working memory in rats: no differences between the sexes

In a number of mammalian species, males appear to have superior spatial abilities to females. The favoured explanations for this cognitive difference are hormonal, with higher testosterone levels in males than females leading to better spatial performance, and evolutionary, where sexual selection has favoured males with increased spatial abilities for either better navigational skills in hunting or to enable an increased territory size. However, an alternative explanation for this sex difference focuses on the role of varying levels of oestrogen in females in spatial cognition (the 'fertility and parental care' hypothesis). One possibility is that varying oestrogen levels result in variation in spatial learning and memory so that, when tested across the oestrous cycle, females perform as well as males on days of low oestrogen but more poorly on days of high oestrogen. If day in the oestrous cycle is not taken into account then, across an experiment, any sex differences found would always produce male superiority. We used a spatial working memory task in a Morris water maze to test the spatial learning and memory abilities of male and female rats. The rats were tested across a number of consecutive days during which the females went through four oestrous cycles. We found no overall sex differences in latencies to reach a submerged platform in a Morris water maze but, on the day of oestrus (low oestrogen), females took an extra swim to learn the platform's location (a 100% increase over the other days in the cycle). Female swim speed also varied across the oestrous cycle but females were no less active on the day of oestrus. These results oppose the predictions of the fertility and parental care hypothesis.     

Dynamics of male residence and female oestrus during a breeding season of blue monkeys in the Kakamega Forest, Kenya

Blue monkeys (Cercopithecus mitis stuhlmanni) are seasonal breeders with a dynamic mating system in which typical one‐male social units are regularly disrupted and replaced by multi‐male ones. The number of males in the group is correlated with the number of oestrous females. We used observations of male presence and female oestrus on individual days during a 6‐month period to assess whether the presence of multiple males in a group stimulates female oestrus or whether oestrous females attract multiple males to the group. We confirmed prior observations with our finding that the number of males in a group was significantly correlated (r_s = 0.435, P < 0.0001) with the number of oestrous females across 126 observation days. A transition matrix did not show an obvious relationship between day‐to‐day changes in the numbers of oestrous females and males. However, cross‐correlation analysis provided stronger support for the idea that the number of oestrous females attracts males to a group than for the idea that the influx of strange males stimulates oestrus in female blue monkeys. Autocorrelation analysis showed that while female oestrus appeared to show a high degree of synchrony, as expected in a seasonal breeder, there was no evidence that the number of males accompanying a group of females influenced the likelihood of other males joining or leaving the group. Overall, our results confirm that female oestrous behaviour stimulates changes in male residence patterns. However, other observations suggest that changes in male residence may also stimulate female oestrus in some circumstances.     

Age at maturity in cavies and guinea-pigs (Cavia aperea and Cavia aperea f. porcellus): influence of social factors

Age at maturity, a particularly important parameter in the life history of small mammals, contributes greatly to fitness. Social influences on age at maturity have been demonstrated for altricial rodents, in particular, mice. Nothing is known about such effects in precocial small mammals. Wild cavies Cavia aperea are born in a highly precocial state and mature early in life, briefly after weaning. We investigated whether the wild cavy C. aperea and the domestic guinea-pig Cavia aperea f. porcellus reach maturity earlier in the presence of adults of the opposite sex. Juvenile females kept in pairs without males showed first vaginal opening (=oestrus) when 59 days old in cavies and at about 40 days in the guinea-pig. However, in the company of adult males, cavy females kept in pairs reached maturity when about 30 days old, and guinea-pig females when 26 days old. Most cavy females experienced successful pregnancy following first vaginal opening. In cavies, female mass at birth and at first oestrus was not correlated with age at first oestrus. In guinea-pigs, birth mass predicted age at maturity only when a male was present. The growth rate from birth to first oestrus related to age at first oestrus. In the wild cavy, the presence of a male appeared to influence maturation more between days 25 and 30 than earlier in life. Male C. aperea matured and had fully descended testes when about 65–70 days old. All male cavies produced abundant motile sperm from day 75. First successful copulations occurred at about the same age. Surprisingly, the priming effect of the presence of an adult male on female maturation proved stronger in these highly precocial caviomorphs than in altricial rodents investigated so far.     

Effects of anosmia on LH secretion,ovulation and oestrous behaviour induced by males in the anovular creole goat

Two experiments were conducted in order to determine the role of the sense of smell in the LH, ovarian and oestrous responses of anovular goats to the introduction of bucks.In Experiment 1, 46 anovular females were allocated to one of three groups after laparoscopy: (C) Control — intact females prevented from contact with males; (I) Intact — intact females allowed contact with males; and (A) Anosmic — females with their sense of smell destroyed by irrigation of the nasal mucosa with ZnSO₄ and subsequently allowed contact with males. Seven days after male introduction, 53% and 20% of the females in groups I and A, respectively, had ovulated, while none of those in group C had ovulated.In Experiment 2, 38 anovular females were allocated to one of two groups after laparoscopy: (I) Intact — intact females allowed contact with males; and (A) Anosmic — females with their sense of smell destroyed as in Experiment 1, and subsequently allowed contact with males. Destruction of the sense of smell did not modify the percentage of females exhibiting an LH pulse after introduction of the male (I: 79% vs. A: 74%), nor did it modify the interval between male introduction and the maximum level of LH (44 min vs. 39 min), the maximum concentration of LH reached (1.97 ng/ml vs. 2.35 ng/ml), or the mean interval between male introduction and onset of oestrus (3.3 days vs. 3.2 days). However, the percentages of females showing oestrus and of females ovulating before day 9 were reduced by the suppression of the sense of smell (I: 89% vs. A: 50%).Therefore destruction of the sense of smell reduced, but did not completely suppress, the response of anovular goats to buck introduction, probably because the females detected the males using other senses.     

Effects of a progestagen on buck-induced short ovarian cycles in the creole meat goat

Two experiments were conducted to determine the effects of progestagens on the buck-induced ovarian cycle in anovular female Creole goats. In the first experiment, 25 anovular females served as a control group and 23 anovular females received a fluorogestone acetate (FGA)-impregnated sponge (45 mg) which was removed at the time males were introduced in the two groups. In the second experiment 10 anovular females served as the control group, and another 10 anovular females received an injection of FGA (5.2 mg) at the time males were introduced. Ovarian activity was traced by laparoscopy (Exp. 1) or progesterone levels (Exp. 2); oestrus and litter size were recorded, and fertility was calculated. In Exp. 2 blood samples were taken every 4 h to study the buck-induced preovulatory luteinizing hormone (LH) surge, and twice daily for progesterone plasma levels.FGA pretreatment did not modify the percentage of females ovulating in either experiment. The percentage of females showing oestrus at first ovulation in Exp. 1 was enhanced by treatment (55% vs 100%), and in both experiments FGA pretreatment restored the normal lifespan of corpora lutea compared to untreated females (96% vs 14%). FGA injection delayed the onset of oestrus and the preovulatory LH surge by 20 h, but did not modify either duration of oestrus or duration of the LH surge.Fertility of control females was low at first ovulation compared to FGA-treated females (10% vs 85%); but fertilization occurred at the subsequent ovulations in most of the control females.It is concluded that progestagen pretreatment is an efficient technique to control buck-induced short ovarian cycles. The exact role of the progestagen, through a delay of LH surge or a direct effect on follicles, remains unknown.     

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.