Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “ESTRUS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8Linked to original sources
PubMed1986

Estrus synchronization systems involving prostaglandin F(2alpha) and progesterone pretreatment in beef heifers.

Two trials were conducted to evaluate treatments combining progesterone pretreatment and prostaglandin F(2alpha) (PGF(2alpha)) on estrus response, pregnancy and calving rate in heifers. Treatments in Trial 1 were 1) control (T(1); n=59), 2) 25 mg PGF(2alpha) on Day 0 (T(2); n=58), 3) 150 mg progesterone (P(4), i.m.) in corn oil on Day -24 plus PGF(2alpha) (T(3); n=61), and 4) 150 mg P(4) on Day -5 plus PGF(2alpha) (T(4); n=59). Trial 2 had T(2) and T(4) only. Heifers were artificially inseminated 8 to 16 h after detection of estrus for 10 and 5 d in Trials 1 and 2, respectively. In Trial 1 more heifers in T(3) and T(4) showed estrus by 72 h compared to T(1) and T(2). In T(3), percentages were greater at 84 and 96 h than in T(1) and T(2). There were no differences between T(3) and T(4) or T(1) and T(2) over time. Cumulative distributions of responses showed that more heifers in T(3) and T(4) were in estrus by 84 h after PGF(2alpha) than after other treatments, while T(3) showed the greatest total number of heifers in estrus by 84 h; this difference persisted for 180 h. In Trial 2, percentages of heifers observed in estrus for T(1) and T(4) were not different. Average interval from PGF(2alpha) to estrus was shorter in Trial 1 for T(3) heifers compared to other treatments. No difference was observed in interval to estrus for T(2) and T(4) in Trial 2; this interval averaged 58 h. Artificial insemination pregnancy rates were not different among treatments in either trial and averaged 67.4%. In Trial 1, a greater proportion of heifers in T(2), T(3) and T(4) calved by 35 days into the calving season compared to T(1), but in Trial 2 calving rates for T(2) and T(4) were not different. Progesterone pretreatment combined with PGF(2alpha) appeared to enhance estrus synchronization without influencing either pregnancy or calving rates.

Journal Article↗
PubMed1989

The efficacy of estrus detection and fertility following synchronization with PGF2a or synchro - mate- B in Zebu cattle.

Two experiments were carried out to assess the efficacy of estrus detection and fertility in Zebu cattle after synchronization with prostaglandin F2a or a progestagen. The first experiment compared estrus detection rates and fertility following insemination in 42 cows previously synchronized with either 25 mg of PGF2a or with a 6 mg of Norgestomet implant plus 5 mg i.m. of estradiol valerate (SMB). Differences were observed in the percentage of cows detected in estrus (54 vs 95%, respectively, P < 0.05), but not in fertility at the first synchronized estrus (26 vs 15%), nor in the detection rate and fertility at the subsequent estrous period (38 v 47%). The second experiment evaluated the efficacy of estrus detection at different time intervals in 30 cows, comparing estrus synchronized with PGF2a with the subsequent estrous period. The observation periods were continuous, day and night, for 100 h both after PGF2a treatment and from Day 18 of the treatment cycle (Period 1). In addition, the animals were administered PGF2a again on Day 10 of the second cycle and observed continuously from 0600 to 1800 h, and from Day 18 of the treatment cycle (Period 2). Finally, the same treatment regimen was used except that the observation was between 0600 to 0700 h and 1800 to 1900 h (Period 3). No differences were obtained in the percentage of cows detected in estrus in the synchronized and nonsynchronized groups (average 75%); however, accuracy in the detection of estrus in Period 3 differed in the nonsynchronized and synchronized estrus groups by 40% (P < 0.05) compared with the other two, more intense observation periods.

Journal Article↗
PubMed1992

Synchronization of estrus and fertility in beef cattle with two injections of buserelin and prostaglandin.

Postpartum beef cows and heifers in Group 1 received 8 mug of buserelin on Day 0 (the beginning of the experiment) and 500 microg of cloprostenol (PGF) on Day 6 (GnRH I, n=54). In Group 2 (GnRH II, n=54), the females were injected with buserelin on Day 0 (8 microg) and Day 3 (4 microg), and PGF on Day 6 and Day 9 for females not detected in estrus previously. Animals were bred by AI 12 hours after the onset of estrus. Blood samples were collected on Day -11 and Day 0 to assess cyclicity and on Day 3 and Days 6 to 12 to examine luteal activity. Progesterone levels did not differ between the 2 groups between Days 0 to 9. In both groups, the proportion of spontaneous estruses from Days 0 to 6 was reduced. Precision of estrus was higher (P<0.005) in the GnRH II group than in the GnRH I group of cows that were detected in estrus between Days 6 and 9. The synchronization rate, interval to estrus, pregnancy and conception rates were similar in GnRH I and GnRH II groups. The conception rate and interval to estrus were similar in cyclic and acyclic cows. Increasing the number of buserelin injections enhanced the precision of estrus, but not the conception rate, without any detrimental effect on luteal activity and induced more estruses in postpartum acyclic beef cattle.

Journal Article↗
PubMed1993

Use of a vaginal mucus impedance meter to detect estrus in the cow.

Two experiments were conducted to investigate the efficacy of a vaginal mucus impedance meter for the detection of estrus in the dairy cow. In Experiment 1 the positioning of the probe within the vaginal tract was examined in dairy cows (n=6) by measuring mucus impedance at 5-cm intervals during probe withdrawal and comparing these fixed distance measurements with the depth within the vaginal tract at which the lowest impedance measurement was recorded. Measurements at 15 and 20 cm from the vulva were significantly lower than at other fixed depths, but did not show a reduction during estrus. The lowest recording upon withdrawal of the probe, which usually occurred between 15 and 20 cm from the vulva, was significantly lower than at any fixed depth recordings and was reduced proportionate during estrus to 0.14 of its non-estrus value. In Experiment 2 the accuracy of the probe to confirm estrus in cows exhibiting possible estrus signs was examined. Dairy cows (n=191) were inseminated either on the basis of herdsman observation of behavior alone (Treatment A) or on the basis of herdsman observation with cows exhibiting signs of estrous behaviour, but not standing to be mounted, being tested for vaginal mucus impedance (Treatment B). There were no significant treatment differences in the estrus detection rate, conception rate or other reproductive performance parameters. However, in 12% of cows in Treatment B, measurement of vaginal mucus impedance detected an extra estrous event, giving a theoretical increase in the estrus detection rate from 0.67 to 0.74 detected/predicted estrous events. It was concluded that when using a vaginal probe the lowest value in the vaginal tract should be sought, but that using the probe as an adjunct to herdsman's observation would not greatly increase estrus detection rate.

Journal Article↗
PubMed1993

Inhibition of estrus and corpora lutea function with Norgestomet.

Forty-five nonpregnant, nonlactating, Angus and Brangus cows were utilized to determine how long a Norgestomet ear implant would inhibit estrus when administered at various stages of an estrous cycle. All cows completed a nontreated estrous cycle to ensure normal cyclicity. At the second observed estrus (estrus = Day 1), cows were randomly allotted to be treated at metestrus (Day 3 or Day 4, n = 15); at diestrus (Day 9 or Day 10, n = 14); or at proestrus (Day 15 or Day 16, n = 16). All cows received a 2-ml intramuscular injection of 3 mg of Norgestomet accompanied by a 6-mg Norgestomet ear implant, which remained in situ for 21 days, or until individual cows were observed in estrus. Estrus was inhibited for a mean (+/- SEM) of 18.7 +/- 0.7, 19.9 +/- 0.8, and 17.0 +/- 0.8 days, respectively, when cows were treated at metestrus, diestrus, and proestrus (metestrus and diestrus vs proestrus; P < 0.05). Estrus was inhibited for an entire 21-day implantation period in 27, 50, and 38% of cows treated at metestrus, diestrus, and proestrus, respectively (P > 0.10). Norgestomet inhibited estrus in all cows for 11, 17, and 11 days after implantation when treatment was initiated at metestrus, diestrus, and proestrus, respectively (P > 0.10). These data indicate that a 6-mg Norgestomet ear implant effectively inhibits estrus in all cows for a maximum of 11 days, with some cows exhibiting estrus by Day 12 with the Norgestomet implant in situ.

Journal Article↗
PubMed1995

Pentobarbital anesthesia during the proestrous afternoon blocks lactotroph proliferation occurring on estrus in female rats.

Estradiol stimulates the synthesis and secretion of PRL and lactotroph proliferation, and its long-term administration induces PRL-secreting pituitary tumors. We examined changes in the number of proliferating lactotrophs throughout the estrous cycle in female rats and the involvement of the brain in the regulation of the lactotroph proliferation by anesthetizing with pentobarbital. Female rats revealing regular 4-day estrous cycles were injected ip with the thymidine analog 5-bromo-2'-deoxyuridine (BrdU) 3 h before decapitation to label DNA-replicating cells. Dispersed anterior pituitary cells obtained from these rats were stained for PRL and BrdU with a double labeling immunofluorescence technique. The rate of lactotroph proliferation was represented by the BrdU-labeling index (BrdU-labeled lactotrophs as a percentage of total lactotrophs counted). Lactotrophs from rats injected with BrdU at 1000 h showed a high BrdU-labeling index of 2.6% on estrus, whereas they showed almost undetectable levels of the BrdU-labeling index during the other stages of the estrous cycle. The anterior pituitary cells other than lactotrophs were scarcely labeled during any stages. The BrdU-labeling index began to rise by the midnight between proestrus and estrus, peaked between 0800 and 1200 h, and returned to undetectable levels by the midnight between estrus and diestrus I. Pentobarbital (35 mg/kg, i.p.) injected at 1345 h on proestrus, which was effective in blocking ovulation on estrus, eliminated completely the increase in the BrdU-labeling index as determined by BrdU injection at 1000 h on estrus. In contrast, the high BrdU-labeling index on estrus was partly suppressed to a level of 1.4% by pentobarbital injection at 0900 or 2100 h on proestrus. The rats injected with pentobarbital at 1345 h on proestrus did not show any increases in the BrdU-labeling index even after BrdU injection was delayed from 1000 to 1400 h on estrus. However, a high BrdU-labeling index of 3.7% was obtained in these animals when BrdU was injected at 1000 h on diestrus I. We conclude that 1) lactotrophs of cycling female rats proliferate selectively on the day of estrus; and 2) the proliferation of lactotrophs on estrus is not due to a direct action on the anterior pituitary of estradiol secreted from the ovaries but triggered by neural events occurring during the proestrous afternoon, which are closely related with the regulation of preovulatory surges of gonadotropin and PRL secretion.

Anesthesia↗
PubMed1984

Prostaglandin F2 alpha for lactating dairy cows with a palpable corpus luteum but unobserved estrus.

Two experiments in 17 dairy herds were for the effectiveness of prostaglandin F2 alpha (treatment) in reducing luteolysis and inducing intervals to conception of 308 cycling lactating dairy cows. Cows with unobserved estrus before first insemination (Experiment 1) and nonpregnant cows with unobserved estrus after insemination (Experiment 2) were eligible for treatment. Cows in Experiment 1 were assigned alternately either to an untreated control group of 85 or to a group of 138 that received 25 mg prostaglandin F2 alpha after detection of a corpus luteum by ovarian palpation. Cows were inseminated either at estrus or at 72 and 96 h posttreatment in the absence of detected estrus. Intervals from treatment to estrus, to first service, and to conception were longer for controls than for treated cows. Conception at first service was similar for controls (39%) and for treated (43%) cows. Procedures were similar for Experiment 2. Intervals from treatment to estrus and treatment to first service were longer for control cows, and treatment to conception tended to be longer for 39 controls than for 46 treated cows. Conception at first service was similar controls (52%) and treated (44%) cows. Prostaglandin F2 alpha was 91% effective for inducing luteolysis based on progesterone concentrations in blood serum. Successful treatment was dependent upon accurate diagnosis of a functional corpus luteum. Days from treatment to conception were reduced for cows with unobserved estrus if treated cows were inseminated at estrus or by appointment in the absence of detected estrus.

Animals↗
PubMed2026

Saliva-based RT-LAMP assays support heat shock protein 70 as a promising transcript marker for estrus identification in buffaloes.

Buffaloes do not exhibit overt estrus signs particularly during summer, leading to a significant economic loss to farmers. Previous studies have identified several candidate transcripts (HSP70, TIMP1, TLR4 and HSD17B1), abundant in buffalo saliva during estrus stage. However, there is no widely applicable technology for estrus detection targeting these transcripts. Therefore, the present study aimed to develop reverse transcription loop mediated isothermal amplification (RT-LAMP) assays for these candidate transcripts using buffalo saliva. Saliva samples were collected from 10 cyclic buffaloes and RT-LAMP assays were optimized for salivary RNA as well as direct saliva. Among the four candidate transcripts, HSP70 showed a statistically significant colour change (p-value&#x2009;=&#x2009;0.0191) at the estrus stage compared to the diestrus stage. This abundance of HSP70 was also supported in large simulated population datasets (10,000 animals) generated using R. Further, the RT-LAMP assays were tested using direct saliva without RNA isolation, and the colour change in the samples during estrus suggested the feasibility of estrus identification using direct saliva, overcoming the tedious step of RNA isolation. The detection of HSP70 using either direct saliva or salivary RNA indicated its potential as a marker for estrus identification. Similarly, TLR4 appeared to be another potential biomarker for RT-LAMP reaction using direct saliva, but it needs further validation in both RNA and direct saliva samples. Overall, the proof-of-concept on RT-LAMP assays optimized for salivary transcripts in the present study would be useful for estrus identification in tropical production systems following further validation on a larger sample size.

Animals↗
PubMed2004

Early-weaned sows: altrenogest therapy, estrus, ovulation, and reproductive performance.

Early weaning is a technique used to increase swine health status, and may cause consequences in reproductive performance of sows. An experiment was performed to evaluate these effects in a herd of sows, with weaning at 9 or 10 days post-farrowing, located in west of Minas Gerais, Brazil. Large-White sows (n=102), with three or four previous parturitions were randomly allocated to three treatment groups: T1: artificial insemination (AI) at first post-weaning estrus of the sows; T2: AI at second post-weaning estrus, T3: AI at first estrus, after an administration of a daily individual dose of 20 mg of altrenogest from 5 to 8 days post-weaning. The duration of the first post-weaning estrus did not differ among treatment groups; however, the second estrus of the T2 group was of shorter duration relative to the other treatment groups (P< or =0.035). Ovulation occurred earlier at the second estrus of the T2 group, compared with the T1 and T3 groups (P< or =0.027), being similar to that at the first estrus of T2 group (P=0.177). The relationship of the timing between ovulation and estrus was similar among treatment groups (P> or =0.221). There was no difference in farrowing rate among treatment groups (P> or =0.313). The T2 group produced a mean of 2.5 more piglets per litter (P=0.002). In conclusion, the use of altrenogest did not increase the reproductive performance of early-weaned sows.

Animals↗
PubMed2000

Effect of sterile service on estrus duration, fertility and prolificacy in artificially inseminated dairy goats.

The effect of sterile service on estrus duration, fertility and prolificacy in artificially inseminated dairy goats during breeding season was studied. Nubian does (n=126) were divided into 2 equal groups: service and control. Estrus was synchronized with intravaginal sponges containing either fluorgestone acetate (FGA; 40 mg) or medroxiprogesterone acetate (MAP; 60 mg) for 12 or 14 d, respectively. Two vasectomized teaser bucks were used to detect estrus at 6-h intervals for 5 d after sponge removal (0600, 1200, 1800 and 2400 h). The teasers were fitted with aprons and permitted to mount all does in both groups, but to penetrate only the service does within the first 12 h of estrus. Does in both groups were inseminated twice at 12 and 24 h after estrus was first detected, using 1 straw per insemination containing 200 million of cooled spermatozoa from 1 buck. The semen was placed in mid-cervix. Estrus duration for the service and control does was (mean +/- SD) 29.4 +/- 6.5 and 41.8 +/- 9.6 h, respectively. Fertility for the service does was 73.7% (46/63); for control does it was 58.7% (37/63). Prolificacy was 2.1 (96/46) and 2.0 (74/37) for service and control does, respectively. Estrus duration (P<0.001) and fertility (P<0.05) differed between the service and control group, but prolificacy was similar (P>0.05). It is concluded that sterile service reduces the duration of estrus and increases fertility in artificially inseminated dairy goats.

Animals↗
PubMed2000

Effect of one spontaneous estrus cycle (after synchronization with PGF2alpha) on reproductive performance in dairy cows.

The objective of the study was to analyze the effect of a spontaneous estrus cycle after synchronization of estrus with prostaglandin F2alpha (PGF2alpha) in dairy cows on the degree of synchronization and reproductive performance. We assigned 557 Holstein cows to two treatment groups. In Group 1 estrus was synchronized by two treatments with 25 mg of Dinoprost-Trometamol in 14-day intervals. Cows were treated 27 to 33 days postpartum (dpp) and 41 to 47 dpp, respectively. Cows in Group 2 were treated with 25 mg of Dinoprost-Trometamol three times in 14-day intervals, starting at 34 to 40 dpp. The second and third injections were administered at 48 to 54 dpp and 62 to 68 dpp, respectively. All cows were inseminated on observed estrus after a voluntary waiting period of 65 days post partum. Thus cows in Group 1 were inseminated on spontaneous estrus and cows in Group 2 on induced estrus. Cows not inseminated at 80 days post partum were palpated per rectum and treated according to a predefined protocol. Herd reproductive performance measures did not differ significantly between groups. The proportion of cows with low serum progesterone levels was significantly higher 3 days after synchronization than 24 days after synchronization (97% vs 39%). The first-service conception rate was 34.8% in Group 1 and 30.7% in Group 2 (P > 0.05). Days open were 113.5 in Group 1 and 110.9 in Group 2 (P > 0.05). It is concluded that postponing artificial insemination for one spontaneous estrus cycle after synchronization decreased the degree of synchronization. This procedure, however, had no effect on herd reproductive performance compared to insemination on first observed estrus after synchronization.

Animals↗
PubMed1985

An investigation of skin temperature differentials in relation to estrus in dairy cattle using a thermal infrared scanning technique.

To evaluate the effectiveness of thermal infrared scanning as a technique to detect estrus, 27 Holstein-Friesian cows were observed for a 90-d period beginning in the second week postpartum. The area enclosed by the 37-C isotherm on the gluteal region of a cow's body tended to increase in association with the occurrence of estrus. This increase became statistically significant at the third postpartum estrus. During the first 50-postpartum d, infrared scanning enhanced detection of estrus when compared with standard dairyman-detection accuracy. However, detection of estrus using infrared scanning was hampered by false positives (33% around the third postpartum estrus) and inability to detect estrus for some cows (7%). It appears at present that the usefulness of infrared scanning for routine detection of estrus in dairy cows is limited, but the technique may have potential as a research tool for the study of skin temperature patterns.

Animals↗
PubMed1986

Synchronized estrus and fertility of beef cows after weaning calves for short intervals.

In Exp. 1, the objective was to determine if interval of separating calves from cows (24 or 48 h) immediately before insemination affects detection and precision of estrus and pregnancy rates of lactating beef cows implanted with norgestomet. Separation of calves from cows for 24 h (n = 418) lengthened intervals to estrus, did not affect precision of estrus, reduced success of detecting estrus and lowered pregnancy rates relative to positive controls (48 h separation, n = 508). Cows with poor body condition, and not suckled for 24 h, conceived at lower rates than cows with similar condition that were not suckled for 48 h. Adverse effects of separation for only 24 h on fertility are apparently due to inadequate intervals between estrus and insemination at 48 h after removing implants. In Exp. 2, the objective was to determine effects of separating calves from cows for 48 h immediately before insemination on detection and precision of estrus and on pregnancy rate of ovulatory lactating beef cows injected twice with prostaglandin F2 alpha (PGF2 alpha). Weaning increased detection of estrus but overall pregnancy rates did not differ between suckled (n = 256) and nonsuckled (n = 221) cows. But, weaning calves improved pregnancy rates of young (2 to 3 yr) cows and reduced fertility among middle (4 to 6 yr)-aged cows. Increased pregnancy rates after weaning calves for 48 h are due largely to greater detection of estrus and inseminating more cows.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2005

Short communication: Conception rates following detection of estrus and timed AI in dairy cows synchronized using GnRH and PGF2alpha.

The objective of this study was to compare conception rates of cows exhibiting spontaneous estrus and receiving artificial insemination (AI) before completion of a timed AI protocol with cows that did not display estrus spontaneously, but were inseminated after 1 of 3 GnRH-PGF2alpha protocols. Cows (n = 432) in 2 herds were administered GnRH on d -7 and were tail-chalked daily. Cows detected in estrus before d 0 were inseminated immediately. Cows not detected in estrus by d 0 were administered PGF2alpha and were tail-chalked daily until 48 h after PGF2alpha. Cows detected in estrus from d -7 to 48 h after PGF2alpha were inseminated and designated as treatment A (n = 46). Cows not detected in estrus and not inseminated by 48 h after PGF2alpha were assigned randomly to receive either GnRH 48 h after PGF2alpha and timed AI 16 h later (treatment B; n = 132), or GnRH and timed AI 64 h after PGF2alpha (treatment C; n = 127), or timed AI 64 h after PGF2alpha (treatment D; n = 127). Pregnancy was diagnosed 38 to 45 d after AI by palpation per rectum of uterine contents. Nearly 11% of all cattle exhibited spontaneous estrus and received immediate AI. Herd did not influence the percentage of cows detected in estrus and inseminated. Conception rates did not differ among treatments. Conception rates differed between herds, but no interaction of herd x treatment was detected. No differences were detected between herds for days in milk, milk production, AI service number, or parity.

Animals↗
PubMed1984

Changes throughout estrous cycles of variables that might indicate estrus in dairy cows.

Two experiments examined physiological changes throughout estrous cycles of Holstein cows. In experiment one, changes were characterized for physical activity, vaginal pH, vaginal temperature, milk yield, heart rate, and concentration in blood plasma of progesterone and 13,14-dihydro-15-keto-prostaglandin F2 alpha. Variables were measured daily in 11 cows through a total of 28 estrous cycles. Cows in estrus at least once postpartum were used. Observations for estrus were at least twice daily. Variables changed significantly with day of estrous cycle. Changes of progesterone, physical activity, and 13,14-dihydro-15-keto-prostaglandin F2 alpha were more marked around estrus than were changes of the other variables. Peaks of physical activity coincided with estrus in 75% of the cases. Experiment two was to determine if increased physical activity, measured with pedometers, coincided with estrus in commercial dairy herds. Cows on 14 farms in New York were fitted with mechanical pedometers, and the pedometers were read at each milking. Readings from 3 days before until 3 days after estrus were used from 55 estrous periods identified by the producers. Physical activity was maximal on day of estrus in 73% of the estrous periods. Increased physical activity of commercial dairy cows agreed well with the producers' diagnoses of estrus. Pedometers could be a valuable component of an estrous detection program.

Animals↗
PubMed1998

Luteolysis during two stages of the estrous cycle: subsequent endocrine profiles associated with radiotelemetrically detected estrus in heifers.

Our objective was to correlate hormonal changes with the timing and onset of estrus in heifers before and after luteolysis was induced with PGF2 alpha at two stages of the estrous cycle: d 6 to 9 (early; n = 10) or d 14 to 15 (late; n = 10). Blood was collected at intervals of 2 or 12 h to quantify serum concentrations of progesterone, estradiol-17 beta, and LH while heifers were observed visually for estrus and monitored for standing activity by pressure-sensitive, radiotelemetric devices. Although the concentrations of estradiol-17 beta that were associated with the putative appearance of the first dominant follicle declined before luteolysis was induced early in the cycle, some heifers that were given PGF2 alpha were in estrus as early as 35 h. Compared with heifers treated late in the estrous cycle, heifers that were treated early in the cycle produced less progesterone before PGF2 alpha treatment and had greater peak concentrations of estradiol-17 beta at estrus. In addition, heifers that were treated early in the cycle had shorter intervals from PGF2 alpha treatment to estrus, to peak estradiol-17 beta, and to peak LH and to initiation of estrus after the peak in estradiol-17 beta than did heifers treated later in the cycle. The increase in estradiol-17 beta associated with the putative first-wave follicle of the subsequent cycle and the duration of that cycle in early cycle heifers was less than after late cycle luteolysis. Results indicated that greater concentrations of estradiol-17 beta during estrus may be related to the durations of previous cycles and less progesterone exposure before luteolysis. The onset of estrus corresponded closely to, but preceded, the preovulatory LH surge by approximately 3 h.

Animals↗
PubMed1983

Effects of an anti-androgen and 5 alpha-reductase inhibitors on estrus duration in the cycling female rat.

Five experiments examined the role of circulating androgens in the control of sexual behavior (lordosis) in the intact cycling rat. The androgen receptor blocker, flutamide (FLU), was administered daily to cycling rats beginning on the day of estrus, and lordotic responsiveness was measured on the 2nd subsequent proestrus day and on the day of estrus. FLU-treated females showed significantly higher levels of lordosis throughout the end of the period of estrus than controls (Experiment 1). Neither the maximal levels of lordosis seen on the evening of proestrus nor the time of onset of estrous responsiveness during the preceeding afternoon were affected by FLU (Experiment 2). Serum estradiol concentrations seen on the morning of proestrus (Experiment 3) did not differ between FLU- and vehicle-treated animals. The weak 5 alpha-reductase inhibitor, testosterone-17 beta-carboxylic acid (17 beta C), prolonged slightly, but did not significantly lengthen, the period of estrus (Experiment 4), while the highly potent steroidal 5 alpha-reductase inhibitor, 4 MA, significantly increased the rate at which estrous behavior declined on the day of estrus (Experiment 5). Circulating androgens do not appear to affect the maximal level of sexual receptivity displayed nor the time of estrus onset; however, they may govern the duration of the period of estrus by influencing the rate of estrus termination.

Anilides↗
PubMed2001

Fertile estrus induced in bitches by bromocryptine, a dopamine agonist: a clinical trial.

The dopamine agonist bromocryptine, probably through amplifying gonadotroph (mainly FSH) secretion, was found to be suitable for provoking fertile estrus during the anestrous phase in bitches without functional cycles and/or ovarian activity. We studied estrus induction in 48 bitches after treatment with semisynthetic ergot alkaloid bromocryptine. For habituation a fractional dose of 0.3 mg/bitch was administered for three days followed by larger doses within the range of 0.6 to 2.5 mg/bitch by selecting dose rates on the basis of individual responsiveness and body weight. The long-term daily bromocryptine dose did not exceed 0.6 mg/bitch and 2.5 mg/bitch in small and large sized bitches, respectively. Gradual habituation and individual dose rates have almost completely eliminated the unwanted side effect of emesis. The period between treatment and onset of estrus varied but the average was 19 days. After the onset of estrus bromocryptine administration was usually continued for another 3 to 6 days. Occurrences of estrus, ovulation and pregnancy were monitored by cytological evaluation of vaginal epithelium, rapid ELISA for plasma progesterone and ultrasonography, respectively. Samples for progesterone were taken on Days 7, 9, 12 and 15 and sonograms of ovarian follicles and of fetuses were taken on Days 0, 22 and 35. The bitches involved in the study either regular or irregular cycles. Bromocryptine treatment induced estrus in all of the bitches including 40 of 48 (83%) with ovulation within a regular estrus and 6 of 48 (12.5%) that showed estrus but did not ovulate. Mating or artificial insemination of bitches in their fertile periods twice at two day intervals resulted in an 83% pregnancy rate (40 cases) and 39 (97.5%) of them gave birth to puppies. However, the average litter size was small with 4.8 +/- 1.6 pups.

Animals↗