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PubMed2005

Timing of ovulation in relation to onset of estrus and LH peak in yak (Poephagus grunniens L.).

The objective of the study was to determine the timing of ovulation in relation to onset of estrus and the preovulatory LH peak in yaks. For this purpose, a sensitive LH enzymeimmunoassay previously established in buffaloes was successfully validated for measuring the hormone in yak plasma. Plasma LH and progesterone were estimated from blood samples collected from eight non-lactating cycling yaks at 2 h intervals after estrus onset until 6 h after ovulation (ovulation was confirmed by palpation of ovaries per rectum). The mean+/-S.E.M. preovulatory plasma LH peak was 10.11+/-0.35 ng/ml with the values ranging from 8.75 to 11.51 ng/ml in individual yaks. The mean+/-S.E.M. duration of the LH surge was 7.25+/-0.55 h with a range of 6-10 h. Onset of LH surge (mean+/-S.E.M.) occurred 3.0+/-0.65 h after the onset of estrus. Mean plasma progesterone stayed low (<0.25 ng/ml) during the entire duration of sampling. Ovulation occurred 30.5+/-0.82 h (range, 28-34 h) after the onset of estrus and 20.25+/-1.03 h after the end of LH surge. The occurrence of the LH peaks within a narrow time frame of 4-8h post estrus onset in yaks could have contributed to the animals ovulating within a narrow time interval.

Animals↗
PubMed2006

Mast cells accumulate in the anogenital region of somatosensory thalamic nuclei during estrus in female mice.

Mast cells are located in the mammalian thalamus where their numbers are sensitive to reproductive hormones. To evaluate whether differences between sexes and over the estrus cycle influence the nuclear distribution of mast cells in mice, we mounted a comprehensive analysis of their distribution in males compared to females and in females over the estrus cycle. Compared to males, mast cells were more numerous in the lateral intralaminar and posterior nuclei of females during estrus and in the ventral posterolateral (VPL) and medial geniculate nuclei during proestrus. During estrus, mast cells were especially concentrated in those regions within the VPL and posterior thalamic nuclei that receive somatosensory information from the anogenital region. Treatment of ovariectomized mice with estrogen increased the number and the percent of mast cells that were degranulated compared to that after ovariectomy alone, an effect that was most apparent in the lateral intralaminar, VPL and posterior nuclei. In estrogen-primed, ovariectomized females, progesterone delivered 5 h before tissue collection counteracted the effects of estrogen. Cromolyn, a mast cell stabilizer, injected centrally 1 h prior to and 24 h after estrogen in ovariectomized mice, prevented the increase in number of mast cells in the whole thalamus and in the intralaminar, VPL and posterior nuclei. This suggests that estrogen induces hyperplasia by a mechanism that involves mast cell degranulation. Based on the discrete anatomical location of mast cells in areas of somatosensory nuclei that receive anogenital input together with the temporal correspondence of these cells with estrus, mast cells are well situated to influence sensory input in females during mating.

Analysis of Variance↗
PubMed2004

A secondary surge of prolactin on the estrus afternoon.

It has been described that throughout the estrous cycle of the rat, plasma prolactin (PRL) is basal except on proestrus afternoon when a preovulatory surge occurs. However, there have been controversies about PRL levels on the estrus day. Thus, the aim of this study was to evaluate the existence of a secondary surge of PRL on estrus afternoon and correlate it with plasma estradiol levels. The jugular vein of cycling rats was cannulated at 14:00 h on proestrus and a blood sample was withdrawn at 17:00 h for plasma LH measurement and determination of the preovulatory LH surge occurrence. In order to exclude the regular cycling rats that do not present the gonadotropins preovulatory surge and do not ovulate, only rats showing the LH surge on proestrus were considered in this study. Blood samples were collected hourly during estrus from midnight to 9:00 h (group 1) and from 10:00 to 18:00 h (group 2). In group 1, PRL showed a descending profile from midnight to 9:00 h, whereas the estradiol concentrations were constant. In group 2, a secondary surge of PRL was observed in 20 of 25 (80%) rats and plasma estradiol remained constant, but was higher in animals with the PRL surge. Thus the present data suggest the occurrence of a secondary surge of PRL in the afternoon of estrus that seems to be related to plasma estradiol levels of estrus day, which might exert only a permissive role in this surge generation.

Animals↗
PubMed2005

Induction and synchronization of estrus in dogs.

Indications for estrus induction in the bitch include missed breeding opportunities or conception failure, the treatment of primary or secondary anestrus and synchronization of ovulation for embryo transfer programs. Reported methods for canine estrus induction include the use of synthetic estrogens (diethylstilbesterol), dopamine agonists (bromocryptine and cabergoline), GnRH agonists (lutrelin, buserelin, fertirelin, deslorelin, and leuprolide) and exogenous gonadotropins (luteinizing hormone, follicle stimulating hormone, human chorionic gonadotropin, pregnant mare serum gonadotropin, and human menopausal gonadotropin). These methods vary widely in efficacy of inducing estrus, as well as in the fertility of the induced estrus. The applicability of some of these methods for clinical practice is questionable. This review will summarize published reports on estrus induction and synchronization in bitches and summarize preliminary results using a long-acting injectable preparation of deslorelin.

Animals↗
PubMed2005

Seasonal effects on attempts to synchronize estrus and ovulation by intravaginal application of progesterone-releasing device (PRID) in mares.

To investigate seasonal effects on the efficacy of estrus synchronization in mares, we administered a progesterone-releasing device (PRID) intravaginally to eight Haflinger mares for 11 days. In January 3 of 8 mares responded to the treatment with estrus and ovulation, in March 7 with estrus and 6 of 7 mares with ovulation, in June 6 of 7 and in October 7 of 8 mares with estrus and ovulation. Follicle distribution patterns at PRID insertion were different between January/October, March/June and June/October (P<0.05). Number of follicles decreased during PRID treatment in January, March and June (difference of number of follicles at Day 12 minus number of follicles at Day 1: -4.2+/-2.7, -0.9+/-0.9 and -4.9+/-1.5 follicles), while it increased in October (3.9+/-1.2 follicles; P<0.05). Mean progesterone concentrations were lowest in January (0.3+/-0.1 ng mL(-1)) when compared with March (3.5+/-1.8 ng mL(-1); P=0.063), June (4.4+/-1.4 ng mL(-1); P<0.05) and October (2.2+/-0.9 ng mL(-1); P<0.05). At Day 2 of PRID treatment, mean progesterone concentrations significantly increased in all mares. Except from January, mean LH concentrations decreased within one day after PRID insertion and remained at low levels during treatments in January and March. Total secretion of LH during PRID-treatment was significantly lower in January and March when compared with June and October. In the 5 of 7 mares that ovulated during PRID treatment a distinct increase of plasma LH concentrations after ovulation was detected. Administration of the progesterone releasing intravaginal device PRID combined with the PGF2alpha analogue cloprostenol was able to induce estrus and ovulation in mares at different times of the year. However, efficacy of the treatment was not satisfactory concerning effectiveness in relation to season and synchrony of intervals from removal of PRID to ovulation in mares.

Administration, Intravaginal↗
PubMed2006

Protocols for synchronizing estrus and ovulation in buffalo (Bubalus bubalis): a review.

Poor estrus expression and a prolonged intercalving interval compromise the reproductive efficiency of female buffaloes. These limitations are exacerbated during the hot season, when fertility decreases dramatically. Pregnancy rate decrease further because difficulties in detecting estrus. To improve reproductive efficiency, several protocols of estrus and ovulation synchronization have been developed. These procedures are based on manipulating the CL, either to induce premature luteolysis using prostaglandins or to prolong the luteal phase using progestagens. However, it has recently emerged that a more precise manipulation of follicular development may be needed to achieve better synchrony of ovulation and improve fertility. Researchers have therefore turned their attention to evaluating programs in which hormones such as GnRH, FSH, LH, eCG, hCG, prostaglandins, progesterone and estradiol are administered. This review considers the impacts of estrus and ovulation synchronization protocols on fertility in the buffalo. In general, it may be stated that buffaloes respond well to the exogenous administration of hormones, and artificial insemination is possible at a pre-established time after synchronizing ovulation. Most combined hormone protocols give satisfactory pregnancy rates, comparable to those achieved in animals inseminated at natural estrus.

Animals↗
PubMed2001

The effect of estradiol benzoate on synchrony of estrus and fertility in cattle after removal of a progesterone-releasing intravaginal device.

The aim was to determine the effect of estradiol benzoate (EDB) given after removal of a progesterone-releasing intravaginal device (PRID) at either emergence or dominance of a follicle wave, on the interval to estrus, variation in its onset and pregnancy rate in heifers. Heifers (n=186) were assigned randomly to four treatments in a 2 x 2 factorial design; emergence or dominance of a follicle wave at PRID removal, with or without 0.5 mg EDB 24 h after PRID removal. Ovarian ultrasonography was performed to confirm follicular status; data from heifers of undeterminable follicular status were excluded (n=36). Mean size of the largest follicle of the new wave at PRID removal was smaller (P < 0.01) in heifers given EDB at emergence (6.3 +/- 0.09 mm) compared with those given it at dominance (10.9 +/- 0.30 mm). The onset of estrus was earlier (P < 0.01) in heifers given EDB at dominance (median 42 h, range 13 h) compared with those not given EDB at dominance (median 43 h, range 42 h). The median interval to estrus was decreased (P < 0.01) in heifers given EDB at emergence (median 48 h, range 73 h) compared with those not given EDB at emergence (median 66 h, range 45 h). Variation in onset of estrus was reduced (P < 0.05) in heifers given EDB compared with those not given EDB. The pregnancy rate was not affected when EDB was given at dominance, however, it was decreased (P < 0.05) when given at emergence (23 of 40 vs 26 of 32, respectively). To determine the effect of EDB on follicular dynamics in heifers treated with EDB at emergence, heifers (n=37) were assigned to two treatments: at emergence with or without EDB and their ovaries were examined daily using ultrasonography. Follicular dynamics were not different (P > 0.05) in EDB-heifers compared with untreated controls. Mean serum estradiol was greater (P < 0.01) in EDB-treated heifers compared with controls. In conclusion, 0.5 mg EDB given 24 h after PRID removal to heifers decreased the interval to estrous onset at emergence or dominance, decreased variation in onset of estrus and decreased pregnancy rates when given at emergence of a follicle wave.

Animals↗
PubMed2001

Effect of short-term treatment with bovine somatotropin at estrus on conception rate and luteal function of repeat-breeding dairy cows.

We studied the effect of recombinant bovine somatotropin (rbST) at the time of estrus on progesterone concentrations and conception rates of repeat-breeding Holstein cows. We used repeat-breeding cows of varied parity (n = 510). All the animals were clinically healthy and had had at least three unsuccessful services before entering the study. After detection of estrus, the cows were randomly assigned to either a treated (n = 201) or a control (n = 309) group. The animals in the treated group were given rbST (500 mg s.c.) at the time of estrus and again 10 d later. Artificial insemination was performed 12 h after the first detection of estrus. In order to evaluate the effect of rbST on luteal function, blood samples were taken from 10 cows in each group every 3 d for 18 d, starting on the day of insemination (Day 0) to determine progesterone concentrations. Conception rates were significantly higher (P < 0.05) in the cows treated with rbST (29.3%) than in the control cows (16.9%). The effects of rbST were maximal in cows with 8 or more previous unsuccessful services and in cows with 2 to 4 calvings. Progesterone concentrations tended to be higher in nonpregnant cows that were treated with rbST than in those that were not treated. The difference between groups was significant (p < 0.05) on Day 18 after insemination. In pregnant cows there were no significant differences in progesterone concentrations between treated and nontreated animals at any time. Treatment with rbST at estrus improved the conception rate of repeat-breeding Holstein cows. This effect was associated with an increase in circulating progesterone concentrations on Day 18.

Animals↗
PubMed2002

Use of progestagen-gonadotrophin treatments in estrus synchronization of sheep.

The main objective of this study was to investigate the effectiveness of certain progestagen-gonadotrophin treatments on synchronization of estrus in sheep. In Experiment I, 30 Chios ewes were treated at the beginning of the breeding season with medroxyprogesterone acetate (MAP) intravaginal sponges for 12 days and a single i.m. treatment of either FSH (Group 1,10 IU, n = 8; Group 2, 5 IU, n = 8; Group 3, 2.5 IU, n = 8) or eCG (Group 4, 400 IU, n = 6) at the time of sponge removal. Ten days after sponge removal laparotomy was performed to record ovarian response. Clinical estrus was observed in more (though not at a significant level) FSH treated than eCG treated sheep (62.5% versus 33.3%). Administration of 400 IU eCG resulted in the highest mean number of CL perewe ovulating (2.8 +/- 0.2), with administration of 10 IU FSH producing the next best results (2.1 +/- 0.3). Statistically significant differences in the mean number of CL per ewe ovulating were found only between ewes in Group 3 (1.7 +/- 0.4) and Group 4 (2.8 +/- 0.2) (P < 0.05). In Experiment II, 53 Chios and 30 Berrichon ewes were treated during the mid-breeding season with MAP intravaginal sponges for 12 days and a single i.m. treatment of either 10 IU FSH (27 Chios and 16 Berrichon ewes) or 400 IU eCG (26 Chios and 14 Berrichon ewes), at the time of sponge removal. Ewes that were in estrus on Days 2-4 and 19-23 after sponge removal were mated to fertile rams. No significant differences were recorded between treatment or breed groups in the proportions of ewes observed in estrus after treatment. In the Berrichon breed, FSH administration resulted in higher lambing rates (93.8% versus 57.1%, P < 0.05) and higher mean number of lambs born per ewe exposed to rams (1.4 +/- 0.2 versus 0.8 +/- 0.2, P < 0.05) than that of eCG. After treatment with eCG, the mean number of lambs born per ewe exposed to rams was higher in the Chios than the Berrichon breed (1.4 +/- 0.2 versus 0.8 +/- 0.2, P < 0.05). After treatment with FSH, the lambing rate was higher in the Berrichon than the Chios breed (93.8% versus 63.0%, P < 0.05). In conclusion, a single FSH treatment (5 or 10 IU) at the end of progestagen treatment appears to be more effective than eCG for the induction of synchronized estrus in sheep at the beginning of the breeding season, with no cases of abnormal ovarian response observed. During the mid-breeding season FSH (10 IU) appears to be equally as effective as eCG (400 IU) in respect of lambing rate and mean number of lambs born per ewe.

Animals↗
PubMed1998

Induction of fertile estrus in bitches using a sustained-release formulation of a GnRH agonist (leuprolide acetate).

A single subcutaneous injection of a sustained-release formulation of a potent GnRH agonist, leuprolide acetate (LA; [D-Leu6, Pro9NEt]-GnRH), was evaluated as a method of inducing fertile estrus in 12 mature anestrous and 6 prepubertal beagle bitches. The bitches were treated with microencapsulated LA (100 micrograms/kg, s.c.) at 120 or 150 d post partum, or at 1 yr of age, followed by a GnRH-analogue (fertirelin; [Pro9NEt]-GnRH, 3 micrograms/kg, i.m.) on the first day of induced estrus. Signs of estrus were seen within 10.3 +/- 0.9 d after LA administration in all bitches. The interestrous interval in 120- and 150-d post-partum bitches was shortened (P < 0.05) to 191 +/- 3 and 222 +/- 3 d, respectively, compared with 264 +/- 11 d in control bitches. All LA treated dogs demonstrated behavioral estrus and mated. Three of 6 (50%) at 120 d post partum, 6 of 6 (100%) at 150 d post partum and 5 of 6 (83%) of prepubertal (1-yr old) bitches then became pregnant and produced a mean litter size of 4.1 +/- 0.8 pups. A normal circulating estrogen and progesterone response pattern was observed in mature anestrous bitches. A prepubertal bitch that failed to become pregnant had a similar estrogen response pattern but an insufficient progesterone profile. The results suggest that microencapsulated LA can be useful in inducing fertile estrus in the domestic dogs.

Anestrus↗
PubMed2003

Pro-apoptotic signals of the bcl-2 gene family in the rat uterus occurs in the night before the day of estrus and precedes ovulation.

Although regression of the endometrium during the rat estrous cycle is a well-recognized event, little is known concerning the mechanisms involved in triggering apoptosis in the rat uterine epithelium. In an attempt to have a better understanding of the mechanisms underlying apoptosis during estrus, we evaluated the expression of several key apoptotic genes of the bcl-2 family during the transition from proestrus to estrus day in the rat. Our results show significant changes in the expression of bcl-2 family genes at midnight before estrus, characterized by a significant increase in the pro-apoptotic ratios: Bax/Bcl-2 and Bcl-xS/Bcl-xL at both mRNA and protein levels. Our results indicate the existence of a positive relation between apoptosis and pro-apoptotic ratios of bcl-2 gene family expression, during the transition from proestrus to estrus day. Importantly, pro-apoptotic signals were detected before ovulation occurred. The overall results suggest that the apoptotic process of the rat endometrium begins at midnight before the day of estrus, may be mediated by Bcl-2 family genes, and precedes ovulation.

Animals↗
PubMed2002

Lactational estrus induction in the Mexican hairless sow.

The purpose of this study was to determine the effects on the reproductive performance of the Mexican hairless pig (MHP) while inducing fertile lactational estrus. Lactational estrus was induced on day 8, postpartum, in 20 primiparous sows during two consecutive reproductive cycles. Boar presence and temporary litter withdrawal were used as stimuli. Group I did not receive stimuli (control, C); group II had a 15 min boar stimulus (B); group III had litter withdrawal for 4 h (LW), and group IV received both stimuli (B + LW). Fertile estrus was detected by sow behavior, exfoliative vaginal cytology, and 17 beta-estradiol and progesterone samples. Individual stimuli did not induce fertile lactational estrus; nevertheless, when used together, both stimuli induced 100% of females into estrus, and 80% of them got pregnant while lactating. The partial withdrawal of the litter had a significant and positive effect on the number of live born piglets. Sows pregnant during lactation had shorter reproductive cycles, by not having non-productive days and litter size was greater. Pregnancy induction during lactation allowed the Mexican hairless sow to reduce the period between parturition's without diminishing the lactation length and litter performance.

Animals↗
PubMed2002

Efficacy of PGF(2alpha) to synchronize estrus in water buffalo cows (Bubalus bubalis) is dependent upon plasma progesterone concentration, corpus luteum size and ovarian follicular status before treatment.

This study was conducted to identify factors affecting PGF(2alpha) efficacy to synchronize estrus in water buffalo cows. After detection of a corpus luteum (CL) by rectal palpation, cows were treated (im) with dinoprost (12.5, 25 or 50mg) or D(+) cloprostenol (75, 150 or 300 microg) in a total of 66 treatments. Blood samples were collected 0, 24 and 48 h after treatment and ultrasound examinations and observations for estrus were performed daily to the day of ovulation or to 6 days after treatment. No PGF(2alpha) dose-response pattern was observed and overall rates of luteal regression (progesterone <1.0 ng/ml at 48 h), estrus, no detected behavioral estrus with ovulation occurring, and ovulation were 71.2, 36.4, 19.7 and 54.5%, respectively. To analyze plasma progesterone concentrations and ovarian dynamics, cows were divided in three groups according to their response to treatment. Cows that failed to have ovulations from a follicle after treatment (Group A, n = 30) had (P < 0.05) a lower plasma progesterone concentration (2.98 ng/ml) and smaller CL area (CLA; 187.3 mm(2)) before treatment as compared with cows that had an ovulation from a follicle (4.43 ng/ml and 223.7 mm(2), respectively; Groups B and C, n = 36). In cows that failed to ovulate, plasma progesterone concentration decreased in the first 24 h, but did not decline further and was >1.0 ng/ml 48 h after treatment. Moreover, no significant change in CLA after treatment was detected, indicating that treatment induced only partial luteolysis. In cows that ovulated, plasma progesterone concentration and CLA decreased continuously from treatment to ovulation (consistent with complete luteolysis). Threshold values of 2.8 ng/ml for plasma progesterone concentration and 189 mm(2) for CLA were identified as the best predictors of ovulation before treatment (83.3 and 80.6% sensitivity and 58.6 and 65.5% specificity, respectively, with positive and negative predictive values around 71%). When the origin of the ovulatory follicle was investigated, the interval from treatment to ovulation was shorter (91.9 versus 113.3 h; P < 0.05), and the ovulatory follicle had a slower growth rate (1.02 versus 1.55 mm per day; P < 0.005), a lesser increase in diameter from treatment to ovulation (4.7 versus 8.0 mm; P < 0.001), and a greater maximum diameter (13.2 versus 12.1 mm; P < 0.05) in cows that ovulated from the largest follicle present in the ovary before treatment (Group B, n = 27) compared with cows that ovulated from the second largest follicle present in the ovary before treatment (Group C, n = 9). In summary, the efficacy of PGF(2alpha) for causing luteolysis and synchronizing estrus and ovulation in buffalo cows was dependent upon plasma progesterone concentration, CL size and ovarian follicular status before treatment.

Animals↗
PubMed1997

Efficiency of the OVATEC unit for estrus detection and calf sex control in beef cows.

Seventy five spring calving Gelbvieh and Angus cows were utilized over a three year period to evaluate the usefulness of the OVATEC intravaginal probe for indicating the onset of estrus and providing the possibility to influence the sex of the offspring by choosing a breeding time in relation to critical changes in cervical mucus conductivity. Cows were randomly assigned by breed each year into one of four treatments: (1) probed and inseminated when impedance values declined, creating conditions expected to favor X-bearing sperm and with it an increase in the conception of females (PF); (2) probed and inseminated when impedance values were rebounding, expected to favor Y-bearing sperms and with it an increase in the conception of males (PB); (3) standing estrus (AI); or (4) natural service by bull (NS). Cows grazed or were fed hay from tall fescue-legume pastures. Lutalyse was used to synchronize estrus in a two injection scheme. Vaginal probe readings were taken at first injection, second injection and every 12 h thereafter for 6 days. Visual observations for estrus were obtained for PF, PB and AI every 12 h postsecond injection. Rectal palpations of ovaries were obtained at standing heat in all but NS treatments. In cycling cows, probe readings increased prediction of estrus onset (P < 0.10) compared to visual observations and were similar (P > 0.95) to rectal palpations in all probed cows. PF cows delivered heifer calves at greater rates (P < 0.025) than all other treatments whereas PB cows delivered bulls at greater rates (P < 0.05) than all other treatments. Heifer to bull ratios were not different (P > 0.95) for AI or NS treatments. The results of this study indicate that the potential exists for increasing female offspring conceptions utilizing cervical mucus conductivity as a gauge for insemination times.

Administration, Intravaginal↗
PubMed1995

Luteinizing hormone (LH) and corticosterone in proestrous afternoon restore the follicle-stimulating hormone secretion at early estrus in adrenalectomized LH-releasing hormone antagonist-treated rats.

Administration of the antiprogestagen RU486 in the morning of proestrus abolishes the secondary surge of FSH during early estrus in the rat without preventing the drop in serum inhibin. In addition, the injection of an ovulatory dose of LH to RU486-injected rats does not restore the secondary surge of FSH. Since RU486 is a potent antiprogesterone with antiglucocorticoid activity, in the first experiment we compared the effects of RU486 and a specific antiprogesterone serum (APS), administered on proestrus, on the secretion of FSH during early estrus. While RU486 and APS reduced the primary surge of LH and FSH, only RU486 abolished the secondary secretion of FSH. In the second experiment, rats injected with LHRH antagonist (LHRHa) and ovine LH (oLH) were adrenalectomized (ADX) or sham-ADX in the morning and injected with corticosterone (B) or oil in the afternoon of proestrus. LHRHa completely eliminated, and oLH restored, the secretion of FSH at 0200 h in estrus. ADX reduced FSH serum concentration at 0200 h in estrus, and B reversed this effect in rats injected with LHRHa and oLH. The results of these experiments indicate that, in the rat, the LHRH-independent secretion of FSH during early estrus is evoked by the combined effects of the preovulatory surge of LH and the rise in serum B on proestrous afternoon.

Adrenal Glands↗
PubMed1996

Vomeronasal organ removal blocks pheromonal induction of estrus in gray short-tailed opossums (Monodelphis domestica).

Estrus is induced in female gray short-tailed opossums (Monodelphis domestica) by exposure to male chemical signals (pheromones). Isolated females remain anestrous, but direct exposure to a male or his scent-marked cage induces estrus within 4-6 days. The objective of this study was to investigate the importance of the vomeronasal organ in detection of and response to estrus-inducing pheromones. The vomeronasal organ was surgically removed through the palate from 8 females (VNX); 5 females (SHAM) underwent sham surgeries in which the vomeronasal organ was exposed but not removed. After a 10-day recovery period, females were placed into male scent-marked cages. Body weight and urogenital sinus cytology were monitored throughout the experiment. All females were anesthetized and perfused with 4% paraformaldehyde 12-13 days after initial pheromone exposure. Vomeronasal organ ablation was evaluated histologically in decalcified snouts. In addition, deafferentation of the accessory olfactory bulb was confirmed by use of a lectin stain specific for the vomeronasal nerve and the glomerular layer of the bulb. All females classified as completely VNX (n = 5) remained anestrous throughout the pheromonal exposure. Incompletely VNX females (n = 2) and all SHAM animals exhibited estrus within 7 days of pheromone stimulation. At perfusion, the mean uterine weight (280.71 +/- 95.6 mg/85 g BW) of SHAM females was greater (p < 0.05) than that of unresponsive, VNX females (133.33 +/- 31.14 mg/85 g). This study demonstrates that the vomeronasal organ is an essential component for transduction of male pheromones required for induction of estrus in a marsupial species.

Animals↗
PubMed1991

Confirmation of estrus rates by palpation per rectum of genital organs in normal repeat dairy cows.

Data were from 6084 normal repeat to second service cows, visually detected in estrus, in a commercial artificial insemination program on a.m./p.m. schedule. The percentage of cows confirmed in estrus by rectal examination and inseminated after palpation was 96.2. The remainder of the cows were not inseminated and non-return rate for these cows was 86.9% (150-day non-return). In cows confirmed in estrus, the percentage of cows ready for service at palpation was 96.1 and the 150-day non-return percentage for these cows (43.9) was different from those cows in which estrus and insemination were considered incorrectly timed (26.7%). These results suggest that the efficiency of reproduction in dairy herds may be improved by examination per rectum of the genital organs at insemination as an effective complement to visual detection of estrus.

Animals↗
PubMed1986

Ovarian steroid regulation of basal pulsatile luteinizing hormone release between the mornings of proestrus and estrus in the rat.

The aim of this study was to examine the regulation of basal pulsatile LH release by ovarian estradiol (E2) and progesterone (P) during the interval between the mornings of proestrus and estrus in the rat estrous cycle. Pulsatile LH release was studied in six groups of rats bled continuously through jugular venous cannulae between 0930-1230 h at a rate of 50 microliter whole blood/5 min: 1) bled on proestrus; 2) sham ovariectomy (OVX) at 0900-1000 h on proestrus and bled on estrus; 3-6) OVX at 0900-1000 h on proestrus, implanted with either empty or E2-, P-, or E2- plus P-containing Silastic capsules, and bled 24 h after OVX. In our colony, plasma E2 levels peaked at 1300 h, remained high through 1730 h, and then declined. Plasma P values increased between 1300 and 1730 h, peaked at 2000 h, and were rapidly declining by 2400 h. To reproduce the magnitude as well as the temporal pattern for these changes in plasma E2 and P levels, E2 capsules were inserted at the time of OVX on proestrus and removed at 1830 h. P capsules were inserted at 1400 h and removed at 2300 h. Groups of ovariectomized or sham-ovariectomized control animals had empty capsules implanted and removed at comparable times. Capsules producing basal E2 and P levels were not inserted after the removal of the original implant, since mean blood LH levels, pulse amplitude, and frequency were the same in rats sham ovariectomized or ovariectomized at 1830 h on proestrus and bled the next morning between 0930-1230 h. Mean blood LH levels decreased between the mornings of proestrus and estrus due to a reduction in LH pulse frequency as pulse amplitude remained stable. OVX at 0900-1000 h on proestrus increased mean blood LH levels 2.5-fold compared to values on estrus due to increases in both LH pulse frequency and amplitude. Restoration of physiological proestrous levels of only E2 returned LH pulse frequency to estrous values, but did not significantly affect LH pulse amplitude. P alone also had no significant effect on LH pulse amplitude, but slightly reduced pulse frequency, although, unlike E2, not to values seen on estrus. Replacing both E2 and P returned LH pulse amplitude to estrous levels and reduced LH pulse frequency.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗