Period Of Sexual Receptivity Research Articles

A Review on Estrous Detection and Associated Challenges in Farm Animals

Estrous detection is the process of identifying when a female animal is in estrus, which is the period of sexual receptivity during the estrous cycle. Accurate and timely detection of estrus is critical for reproductive management in farm animals. This article review focuses on the challenges associated with estrous detection in farm animals and aims to evaluate the various methods of estrous detection, assess the factors affecting estrous detection accuracy, and identify and improve the challenges associated with estrous detection. The review examines the different techniques and technologies available for estrous detection, including visual observation, automated monitoring systems, hormonal assays, and ultrasonography. It also assesses the factors that affect estrous detection accuracy, such as timing, labor requirements, and the use of technology. The review identifies the challenges associated with estrous detection, including accuracy, timing, and labor requirements, and proposes potential solutions. Besides the Researchers and farmers seeking to optimize breeding programs and increase herd productivity can gain valuable insight from this review on estrous detection in farm animals.

Sex hormone levels and expression of their receptors in lactating and lactating pregnant rats

Parturient rats show a postpartum estrus, a period of sexual receptivity that occurs from 6 to 15 h after the birth of a litter, which allows the mother to gestate a second litter while simultaneously nursing the first one (lactating and pregnant). The present study investigated hormone levels and the expression pattern of estrogen receptor α, and β, progesterone receptor isoforms and SRC1 in the hypothalamus and the preoptic area of lactating as well as in lactating-pregnant rats. In the latter, estradiol levels were 3-fold higher than those observed in lactating rats on day 14, meanwhile progesterone levels did not change in any condition. There were higher levels of prolactin in both lactating and lactating-pregnant rats on day 7 and decreased on the following days. In the hypothalamus of the lactating rat, the content of ERα increased during lactation meanwhile that of ERβ decreased 50% on day 10. The content of both estrogen receptor subtypes in the hypothalamus increased 3-fold on day 21 in lactating-pregnant rats. In the preoptic area, the content of ERα was higher in lactating-pregnant rats on days 14 and 21 while the content of progesterone receptor isoforms was lower as compared with those found in lactating animals on days 7 and 10. The content of SRC1 increased 2-fold in the preoptic area only in lactating rats at day 14 and 21. These findings suggest that lactating- pregnant animals should exhibit differential neuroendocrine and molecular characteristics as compared to lactating animals.

Estrous synchrony in a nonseasonal breeder: adaptive strategy or population process?

The idea that female mammals can manipulate the duration of each other’s estrus in an effort to influence the degree of synchrony between their periods of sexual receptivity is a persistent and popularly held one. It is frequently cited as proof of pheromonal communication in humans and often invoked by models of female reproductive strategies more generally. Yet, to date, no tests of the evolutionary arguments put forward by proponents of the phenomenon have been undertaken. We addressed this deficit with an analysis of the reproductive demography of wild female chacma baboons, where variance in the temporal distribution of female receptivity is known to occur. Specifically, we tested the predictions that this variance will reflect female attempts to minimize 1) the risks of being monopolized by a single male or 2) the intensity of interfemale competition for males. Using model comparison, we found no evidence that male number or operational sex ratio had any influence on the distribution of female receptivity, the number of females in estrus, or the duration of female sexual swellings. Indeed, when modeling estrous overlap and cycling female number, we found that a simple nondeterministic model provided the best fit. We conclude, therefore, that variance in the temporal distribution of female receptivity is indicative of nothing more than a population process and that socially mediated synchrony is not a tangible adaptive phenomenon. Key words: female receptivity, population process, sexual selection, socially mediated synchrony. [Behav Ecol]

Facilitation of Lordosis in Rats by a Metabolite of Luteinizing Hormone Releasing Hormone

In the female rat, ovulation is preceded by a marked increase in the release of the decapeptide, LHRH, culminating in a preovulatory LH surge, which coincides with a period of sexual receptivity. The decapeptide, LHRH, is processed by a zinc metalloendopeptidase EC 3.4.24.15 (EP24.15) that cleaves the hormone at the Tyr(5)-Gly(6) bond. We have previously reported that the autoregulation of LHRH gene expression can also be mediated by its metabolite, LHRH-(1-5). Given the central function of LHRH in reproduction and reproductive behavior, we examined the role of the metabolite, LHRH-(1-5), in mediation of LHRH-facilitated reproductive behavior. Intracerebroventricular administration of LHRH-(1-5) facilitated sexual behavior responses, similar to those facilitated by the decapeptide LHRH, in ovariectomized estradiol-primed female rats. Furthermore, immunoneutralization of EP24.15 resulted in the inhibition of the LHRH-facilitated lordosis but had no inhibitory effects on LHRH-(1-5)-facilitated lordosis. The LHRH antagonist, Antide, was capable of inhibiting LHRH-facilitated lordosis, without affecting LHRH-(1-5)-facilitated lordosis. Collectively, these results suggest a role for LHRH metabolites in the facilitation of female receptive behavior in rats.

Stimulation of luteinizing hormone-releasing hormone (LHRH) gene expression in GT1-7 cells by its metabolite, LHRH-(1-5).

Given the central role of the decapeptide LHRH in reproduction and reproductive behavior, it is important to focus on delineating the possible effects of this gene and its products in the regulation of hormone-dependent reproductive processes. In the female, ovulation is preceded by a marked increase in LHRH release; the increase in LHRH release culminates in a preovulatory LH surge, which coincides with a period of sexual receptivity. In contrast to the belief that the proteolytic metabolism of LHRH serves only as a degradative process that removes excess LHRH and attenuates signal transduction through the LHRH receptor, we hypothesized that a metabolite of the decapeptide, LHRH-(1-5), can directly regulate LHRH neuronal function. This study demonstrates the ability of LHRH-(1-5) peptide to regulate LHRH gene expression in the LHRH neuronal cell line, the GT(1-7) cell. The results show that LHRH-(1-5) stimulated LHRH gene expression at the posttranscriptional level. In contrast to the LHRH suppression of its own gene expression, the coadministration of LHRH with the metalloendopeptidase, EC 3.4.24.15, an endopeptidase known to cleave LHRH to form LHRH(1-5), shows a reversal of effect, a stimulation of LHRH gene expression. Finally, the effect of LHRH-(1-5) on LHRH gene expression appears to be mediated by the calcium/calmodulin-dependent protein kinase. The present study supports the hypothesis that the physiological metabolite of LHRH, LHRH-(1-5), is functionally capable of regulating the reproductive neuroendocrine system.

Social regulation of reproduction in the female mound-builder mouse ( Mus spicilegus)

Social environment influences the reproductive physiology and sexual behaviour of the female house mouse Mus musculus. An all-female environment tends to suppress the oestrous cycles, whereas the presence of a male induces and synchronises sexual receptivity. However, reproductive responses to social environment may differ among the various species of rodents. In mound-builder female mice, Mus spicilegus, periods of sexual receptivity are interrupted by periods where adult females display a vaginal closure. We investigated the influence of different social environments on the vaginal opening and oestrous state of adult female M. spicilegus. Result showed that when females were grouped their vaginas were generally closed but that vaginal opening occurred when they were isolated or housed with a sexual partner. Females became sexually receptive when housed with a male, but when isolated their cervical smears did not reach characteristics of the oestrus. In female M. spicilegus, male presence thus has a stimulating effect on oestrous induction. Furthermore, cohabitation with females has an inhibiting effect on vaginal opening.

An analysis of birth sex ratio bias in captive prosimian species.

The extent to which sex ratio bias is a common reproductive characteristic of prosimians has not been well established. The present study analyzed reproduction in 13 breeding groups of captive prosimians for evidence of birth sex ratio bias. A substantial male bias was demonstrated in nongregarious, but not gregarious, breeding groups. Analyses of birth sex ratios of individual mothers suggested that the observed bias did not result from the tendency of a few mothers to overproduce males, but rather from a small but reliable excess of male births in general. An examination of infant mortality revealed that male Otolemur garnettii and Microcebus murinus infants were more vulnerable to preweaning mortality, whereas female Eulemur fulvus albifrons infants were more vulnerable. An analysis of birth order by sex found that mothers of one group (O. garnettii) tended to produce males initially and females later. Additionally, a distinct pattern of birth seasonality was noted among Malagasy prosimians that was absent in the African prosimians. Greater length of period of sexual receptivity for nongregarious females as compared to gregarious females is proposed as a possible mechanism of male birth sex ratio bias. © 1996 Wiley-Liss, Inc.

A Review of Reproductive Rates in Sticklebacks in Relation To Parental Expenditure and Operational Sex Ratios

1. The expenditures of time and energy on parental activities of female and male threespine sticklebacks, Gasterosteus aculeatus L., are reviewed in the context of sex differences in competition for and choice of mates. 2. The female's parental contribution is mainly cytoplasmic in the form of provisioned eggs. In energy units each clutch spawned represents about 200% of the daily maintenance ration of a sexually mature female. Each egg in a clutch represents about 2% of that ration. The 'time out', during which the female is sexually unreceptive between spawnings, varies from about 3 to 15 days, and is inversely correlated with the rate of food consumption. 3. The male's parental contribution is primarily behavioural. The daily energy expenditure of a parental male is equivalent to a daily ration of about 6% of the male's body weight, a value not dissimilar to that of a reproductively active female. The pattern of 'time-outs' of males differs from that of females, with the periods of sexual receptivity and unreceptivity both longer. 4. A crude simulation model of the effect of sex differences in the pattern and length of 'time outs' suggested that the operational sex ratio (OSR) would usually be male-biased favouring inter-male competition for mates and mate choice by females. 5. However, both environmental factors such as food availability, and demographic factors such as sex differences in mortality rates, together with the sex differences in 'time out' could cause the OSR to vary within breeding seasons, between breeding seasons and between populations. This leads to the prediction that there will be corresponding variations in the intensities of male-male and female-female competition for mates and hence in the development of secondary sexual characteristics.

Oestrous cycles, oestrus and ovulation of the zebu in the Mexican tropics.

The length of the oestrous cycle, oestrus and the time of ovulation were assessed in 20 adult, non-lactating zebu cows over 53 consecutive days of observation. Oestrus was detected at 30-minute observation periods daily. Peripheral blood samples were collected twice weekly for progesterone determination. To measure the length of the synchronised oestrous period, 10 cows with a palpable corpus luteum were injected with prostaglandin F2 alpha and continuously observed for 96 hours. Two cows at a time were exposed to a bull with a deviated penis for five minutes every three hours during this period. To measure the length of the natural oestrus, eight of the 10 cows from the previous experiment were continuously observed from day 21 after prostaglandin injection. They were kept during the daytime in a field with two teaser bulls and at night in a cattle pen where they were exposed to a teaser bull every three hours. Oestrus was considered to occur when the cow stood to be mounted. Ovulation was detected by rectal palpation every three hours in five cows starting six hours after receptivity commenced until ovulation took place. The length of the oestrous cycle was 20.1 +/- 1.9 days; 20 per cent of the animals did not show oestrus although their progesterone levels demonstrated that they were cycling. Two cows showed oestrus following prostaglandin F2 alpha injection although they were cycling as revealed by serum progesterone. Five animals showed behavioural oestrus around 118 hours after injection and following their release. Oestrus duration was 15.3 +/- 6.0 hours and ovulation occurred 28.2 +/- 5.0 hours after the start of the period of sexual receptivity.

Scent marking and mate choice in the golden hamster

Test groups consisting of three males and one female were adapted to home areas within a 244×122 cm enclosure for a 4-day period. Subsequently, agonistic interactions and patterns of scent marking were recorded daily for 30 min over the duration of the female's 4-day estrous cycle. Alpha males flank marked significantly more than the two subordinates. The former accounted for over 95% of flank gland marking by males on the two days prior to the female's period of sexual receptivity. The female showed increased frequencies of both flank gland and vaginal marking over the three nonreceptive days of the cycle with the highest frequency of marking occurring 24 hr prior to sexual receptivity. During the two days prior to receptivity, the female both vaginal marked and flank marked significantly more in and about the home area of the alpha male. We conclude that the female hamster shows mate choice prior to the onset of sexual receptivity and that both vaginal marks and flank marks are employed to facilitate mating with the alpha male.

Alteration of sensitivity to progesterone facilitation of lordosis in guinea pigs by modulation of hypothalamic progestin receptors

In order to delineate further the role of the progestin receptor system in the hypothalamus-preoptic area in the regulation of lordisis in female guinea pigs, we injected estradiol benzoate and progesterone in various regimens that result in sensitivity to, desensitization to, or restoration of sensitivity to progesterone-facilitation of lordosis. We attempted to correlate the effectiveness of progesterone to facilitate lordosis with the effectiveness of progesterone to cause accumulation of nuclear progestin receptors measured by an in vitro [ 3H]R 5020 binding assay. A progesterone injection 40 h after an estradiol benzoate injection in ovariectomized guinea pigs resulted in lordosis in 83% of the animals, caused a 30% depletion of cytoplasmic progestin receptors and a 200% increase in the concentration of nuclear progestin receptors 4 h after injection compared with control animals. By 24 h after the injection, after the period of sexual receptivity had terminated, the concentration of nuclear progestin receptors was no longer elevated, and the concentration of cytoplasmic progestin receptors was decreased to a level 55% lower than control animals. This depression was due to a decrease in the concentration of binding sites, not to in vitro competition of the injected progesterone with the [ 3H]R 5020 because similar results were obtained with cytosol in which progesterone had been removed by gel filtration prior to incubation. These progesterone-injected guinea pigs did not respond to a second progesterone injection 24 h after the first (64 h), and the injection resulted in 70% fewer nuclear progestin receptors than in oil-injected controls. This decreased accumulation appears to be due to the decreased level of cytoplasmic progestin receptors brought about by the first progesterone injection. Estradiol benzoate injected concurrently with the first progesterone injection restored behavioral sensitivity to the second progesterone injection and caused 160% greater accumulation of nuclear progestin receptors in response to the second progesterone injection than control animals that had received only progesterone. The increased concentration of nuclear progestin receptors in the estradiol-injected animals appear to be due to increased availability of cytoplasmic progestin receptors. It seems that estradiol increases and progesterone decreases the concentration of cytoplasmic progesterone receptors in hypothalamus-preoptic area such that a subsequent injection of progesterone results in a high or low concentration of nuclear progestin receptors. The accumulation of sufficient nuclear progestin receptors in response to the progesterone injection may be a requirement in the process by which progesterone facilitates lordosis in estradiol-primed rodents.

Midbrain distribution of neurons with strong, sustained responses to lordosis trigger stimuli in the female golden hamster

Midbrain single units in anesthetized female hamsters were examined for pronounced, sustained responses to types of somatic stimuli which control the display of lordosis during periods of sexual receptivity. Units showing strong responses to lordosis trigger stimuli were widely distributed, but tended to be most concentrated in the deep superior colliculus, ventromedial midbrain and central gray, brain regions previously implicated, by other methods, in the control of hamster lordosis.

Progesterone-induced mating behavior in rats on the day following spontaneous heat

Three experiments were designed to test the ability of exogenous progesterone administered shortly after the termination of spontaneous heat to induce a second period of sexual receptivity. In female rats displaying four-day estrous cycles, a second period of sexual receptivity could be induced by exogenous progesterone administered before, but not after, 1100 hrs on the day following spontaneous heat. In a second experiment, animals given coital stimulation on the evening of proestrus were found to exhibit a second period of progesterone-induced receptivity equal in intensity to that of animals not receiving such stimulation. In the final experiment, various amounts of progesterone were administered to ascertain the relationship of dose and response. Dosages of 2.5 mg, 1.5 mg and 1.0 mg were equally effective in inducing mating behavior while a linear decrease was observed with smaller amounts. These results indicate that the neural substrate responsible for lordosis behavior is capable of reacting with progesterone administered early on the morning of the day following spontaneous heat to produce a second period of sexual receptivity.

Mating behavior ofBathyplectes curculionis [Hym.: Ichneumonidae] a parasitoid of the alfalfa weevil,Hypera postica Col.: Curculionidae

We describe the courtship behavior of male and femaleBathyplectes curculionis (Thomson). FemaleB. curculionis are polygamous and sexually receptive for up to 2 days after eclosion. The high activity levels of virgin females combined with their polygamy and long period of sexual receptivity allow for post-dispersal mating which may facilitate maximum gene flow between localB. curculionis populations. This high genetic diversity may be partially responsible for the widespread occurrence ofB. curculionis in North America.

Progesterone: Examination of its postulated inhibitory actions on lordosis during the rat estrous cycle

Three experiments tested whether the inhibitory effects of progesterone could be of physiological significance in regulating the duration of behavioral estrus in female rats. In animals displaying 5 day estrous cycles, a second period of sexual receptivity, one day following the occurrence of spontaneous estrus, could be induced by exogenous hormone administration, regardless of whether the ovaries were intact or were removed during the period over which the exogenous hormones were acting. In a second experiment, acute ovariectomy at various times during the progesterone surge acted only to degrade the quality of receptive behavior subsequently observed, never to enhance it by removing a postulated inhibitory influence. In the final experiment there was some suggestion that progesterone's facilitating effect on lordosis during the later portions of spontaneous estrus were attenuated by prior exposure to ovarian secretions during the early period of behavioral estrus. Our results are consistent with the hypothesis that the duration of receptive behavior under physiological conditions is not primarily regulated by inhibitory actions of progesterone, but rather by the quantity and duration of estrogen secretions during the conditioning period.

The role of progesterone in regulating the period of sexual receptivity in the female hamster.

SUMMARY Spayed female hamsters were given a 150 μg pellet of oestradiol s.c. (day 0). After s.c. placement of a 200 μg pellet of progesterone 7 days later, all animals displayed oestrous behaviour. Treatment with 200 μg progesterone suspended in propylene glycol or sesame oil, on days 4, 5 or 6 also induced an immediate period of heat but subsequent placement of a 200 μg pellet of progesterone on day 7 did not always result in oestrous behaviour. The animals did not show the lordosis response after placement of the progesterone pellet on day 7 when 200 μg progesterone in sesame oil had been given on either day 5 or 6. In contrast, when propylene glycol was employed as the vehicle, only injection on day 6 blocked oestrous behaviour on day 7. When the same amount of progesterone in propylene glycol was administered on day 5, as injections of 50 μg each over 12 h or more, progesterone in propylene glycol was more effective in blocking oestrous behaviour on day 7. The injection on day 5 of 100 μg progesterone in propylene glycol as four injections of 25 μg over 12 h did not block oestrous behaviour on day 7. The injection of 50 μg progesterone in propylene glycol on four successive nights induced a period of sexual receptivity after each injection. These observations indicate that the duration of the insensitive condition, developing as a result of a period of progesterone-facilitated heat, is a function of the amount of hormone causing the initial receptive period, as well as the duration of progesterone stimulation.