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PubMed1999

Estrous cycle characteristics and response to estrus synchronization in mammoth asses (Equus asinus americanus).

Breeding records from a herd of mammoth asses (Equus asinus americanus) maintained on pasture in southeast Texas from 1990 to 1998 were reviewed. Jennies were pasture or hand mated, and estrus was either observed while the jennies were on pasture or when exposed to a jack after being penned. Eighty-one estrus periods and 43 diestrus intervals were recorded in 33 jennies over 4 seasons of the year (January-March, April-June, July-September, and October-December). Estrous cycle length and the duration of estrus were similar among seasons. Over all seasons, estrous cycle length was 23.3 +/- 2.6 d, duration of estrus was 5.9 +/- 2.1 d, and diestrus length was 17.4 +/- 2.6 d (mean +/- SD). During these same 9 yr, 58 injections of PGF2 alpha (5 mg, i.m.) were administered to 38 jennies without regard to stage of estrous cycle. Seventy-six percent (44/58) of the jennies showed signs of estrus after PGF2 alpha treatment, with an interval to estrus of 4.4 +/- 1.6 d and a duration of estrus of 5.6 +/- 1.7 d. Two estrus synchronization schemes were also assessed. Trial 1 was performed in October to November 1996, and Trial 2 was performed in February to March 1998. In Trial 1 (Group PE + PGF, n = 10), each jenny was injected intramuscularly once daily for 10 d with 150 mg progesterone and 10 mg estradiol-17 beta in sesame oil, and PGF2 alpha (10 mg) was injected intramuscularly on the last day of treatment. In Trial 2 (Group PGF-2X, n = 11), each jenny was injected intramuscularly twice, 16 d apart, with 10 mg PGF2 alpha. All Group PE + PGF jennies responded to treatment. One jenny in Group PGF-2X did not respond to either injection of PGF2 alpha, while 2 jennies responded to the first but not the second PGF2 alpha injection (8 of 11 jennies returned to estrus and ovulated after the second PGF2 alpha injection). Duration of estrus was 6.8 +/- 1.9 d for Group PE + PGF and 7.1 +/- 1.8 d for Group PGF-2X jennies. Interval to estrus and interval to ovulation following the last treatment were 9.0 +/- 0.9 d and 14.5 +/- 1.7 d, respectively, in Group PE + PGF jennies, and 4.5 +/- 0.9 d and 10.4 +/- 1.8 d, respectively, for Group PGF-2X jennies. In summary, estrous cycle characteristics of mammoth asses are similar to those reported for standard jennies, and estrus synchronization schemes used in horses are effective in mammoth asses.

Animals↗
PubMed2006

Sex steroid receptor expression in the oviduct and uterus of sheep with estrus synchronized with progestagen or prostaglandin analogues.

The objective of this study was to investigate differences in the expression of estrogen receptor-alpha (ERalpha), progesterone receptor (PR) and the proliferative indexes (Ki-67), in the uterus and oviduct of sheep with estrus synchronized either by prostaglandin analogues (Group PA, n=27) or by treatment with progestagens (Group P, n=29) on days 4 and 7 (day 0=estrus), when the embryos were collected. Immunohistochemical methods were used to quantify ERalpha, PR and Ki-67 in six superficial and deep compartments in the uterus and oviduct. The expression of ERalpha was significantly (P<0.01) lower in progestagen treated ewes than in prostaglandin analogues treated group in the luminal epithelium, superficial glands and superficial stroma in the uterus on day 4. The expression of PR was significantly lower in progesterone treated ewes than in the PA Group in the superficial gland (P<0.05) in both days studied. The lowest expression of PR was observed in the luminal caruncular epithelium and superficial glands in both treatments, obtaining the lowest levels on day 4 (P<0.05). There were significant differences between days 4 and 7 in the Ki-67 immunostaining in the luminal epithelium (P<0.01) and superficial glands (P<0.05). A higher cell proliferation was observed in the uterine epithelium (P<0.05) on day 4 in the animals treated with progestagens. Results indicate that sheep with synchronization of estrus with progestagens showed a reduction of ERalpha and PR protein expression in most of oviductal and uterine cells.

Animals↗
PubMed1994

Estrus synchronization with melengestrol acetate in cyclic ewes. Insemination with fresh or frozen semen during the first or second estrus post treatment.

A total of 540 cyclic ewes were randomly allocated to 1 of 6 groups according to synchronization or not with melengestrol acetate (MGA), insemination with fresh or frozen semen, and insemination during the first or second estrus post treatment. The MGA was effective in synchronizing estrus, since the percentage of ewes showing estrus during the first 6 days after treatment was significantly higher (P<0.05) for treated (79.5%) than for nontreated ewes (33.5%); 74% of the treated ewes showed estrus during a 72-h period. Progesterone concentrations in plasma samples obtained at random from 34 treated ewes on Day 8 post estrus revealed that 94% of them ovulated and formed a functional CL. Synchronization was maintained during the second estrus post treatment, since 71.9% of the ewes showed the second estrus during a 72-h period. Treatment with 0.22 mg of MGA/head/d for 14 d had a detrimental effect on fertility when insemination was carried out during the first estrus post treatment. Delaying insemination until the second estrus post treatment caused a less marked reduction in conception rates. Thus, MGA can be a useful alternative for estrus synchronization of a large number of ewes. Artificial insemination can be delayed until the second estrus post treatment, improving fertility without loosing the advantages of estrus synchronization.

Journal Article↗
PubMed2001

Effectiveness of intravaginal progesterone inserts and FSH for inducing synchronized estrus and increasing lambing rate in anestrous ewes.

The objectives of this study were to determine whether a new progesterone (P4)-releasing intravaginal insert would induce fertile estrus and whether FSH combined with the insert would increase prolificacy in anestrous ewes introduced to rams. Ewes of mixed breeding on six farms were assigned to four randomized treatments: control (C), n = 73; 12 d P4 (polycapralactone [PCL] insert with 0.82 g P4), (P12), n = 73; 12 d P4 plus i.m. FSH (Folltropin, 55 mg NIH-FSH-P1 equivalent) in propylene glycol, 24 h before insert removal, (P12F), n = 71; and 5 d P4 plus FSH (P5F), n = 77. Growth and ovulation of follicles were observed ultrasonographically in 20 ewes at four farms (five/treatment) at insert removal and 36, 48, 72, and 96 h later. Intact rams (1:15 ewes in multiple-sire groups) were joined at insert removal, and raddle marks were observed every 12 h for 5 d. On d 26 to 30, rams were removed; ewes were examined for pregnancy then and 20 d later. Percentage of ewes marked by rams was greater in P4-treated (66 to 79%) than in C (12%; P < 0.01) ewes and in P5F (79%) than in P12F (66%; P < 0.05). Diameters of largest follicles at insert removal were greater (P < 0.05) in P4-treated (5.5 +/- 0.2) than in C ewes (4.8 +/- 0.2). Progesterone increased numbers of follicles > 3 mm (P < 0.01) or ovulated (P < 0.05; 2.6 +/- 0.6 vs 1.3 +/- 0.6 in C ewes) and FSH increased number of follicles > 3 mm (P < 0.05). In FSH-treated ewes, ovulation rate tended to be greater after treatment with P4 for 5 than for 12 d (P = 0.09, 3.3 +/- 0.6 and 2.2 +/- 0.4, respectively). More P4-treated than C ewes lambed (P < 0.01) to the first (38 to 45 vs 0%) or both (63 to 66 vs 41%) service periods. Prolificacy (first service) did not differ between FSH-treated ewes (P12F + P5F; 1.8 +/- 0.1) and ewes treated with P4 only (P12; 1.6 +/- 0.1). However, FSH increased prolificacy to first service (1.8 +/- 0.1) over prolificacy to second service (C ewes 1.5 +/- 0.1; P < 0.05, and all ewes 1.4 +/- 0.1; P < 0.01). Pregnancy retention did not differ among treatments but was greater (P < 0.01) in ewes that conceived at the first (90.9 +/- 3.7) than at the second (72.5 +/- 3.3) service period. In conclusion, a PCL insert in combination with ram introduction at insert removal was more effective than ram introduction alone to induce synchronized estrus and ovulation and to yield pregnancy after one or two service periods. Treatment with P4 for 5 d was as effective as for 12 d to induce fertile estrus in FSH-treated anestrous ewes.

Administration, Intravaginal↗
PubMed1981

[Selection of laboratory rats for fertility components in synchronized estrus using Suisychron-Praemix. 1. Effects of selection and synchronization].

The following results were obtained from experimental studies into effects of selection for fertility and into synchronised oestrus though eight generations of laboratory rats: -- The result of selection recordable from the population with selection only was better than that recorded from the population with selection and synchronised oestrus. This has been attributed to higher correlation between phenotype and genotype in the selection variant. -- Direct negative impact of synchronised oestrus on selection index was recorded from a population with random mating. -- The effects of synchronised oestrus regarding selection success were offset but not entirely ruled out by selection. -- Through the generations of both populations with synchronised oestrus the effects of synchronisation were lowered due to both physiological adaptation to Suisynchron application and contraselection with regard to suitability for synchronisation.

Animals↗
PubMed1995

The effect of estrus synchronization scheme, injection protocol and large ovarian follicle on response to superovulation in beef heifers.

Two trials were conducted to examine the effects of estrus synchronization scheme, gonadotropin injection protocol and presence of a large ovarian follicle on response to superstimulation of follicular development and the ensuing superovulation. Estrus was synchronized with either a progestin compound (MGA) or by the use of a luteolytic agent (PGF). Superstimulation was induced with 280 mg equivalents of pFSH administered either by a single subcutaneous injection or by a series of 8 intramuscular injections over 4 d. Follicular development was followed for 5 d with real-time ultrasound, and the heifers were retrospectively classified as to the presence or absence of a large follicle (> or = 8 mm; morphologically dominant follicle) at the start of superstimulation. The 2 trials differed by season of the year and genetic origin of the heifers. In Trial I (20 heifers), the ovulation rate was influenced by the 3-way interaction of the synchronization scheme, injection protocol and morphologically dominant follicle (P = 0.05). The number of large follicles on Day 5 (Day 0 = day of start of superstimulation) and ovarian score (scale 1 to 5 based on extent of follicular development; 1 = least, 5 = most) on Day 5 were significantly correlated (P < 0.05) with ovulation rate. In Trial II (20 heifers), the ovulation rate, number of embryos recovered, number of transferable embryos and ovarian weights were all greater (P < 0.05 to P < 0.01) with the 8-injection protocol than the 1-injection protocol. The number of medium follicles (5 to 7 mm) on Days 2 and 3, number of large follicles (> or = 8 mm) on Days 3, 4 and 5 and ovarian scores on Days 4 and 5 were all significantly correlated (P < 0.05) with ovulation rate. In both trials, differences in follicle populations were not seen until Day 3 of the superstimulation procedure. Collectively, these trials do not provide strong support for a single injection of FSH, as used here, nor does it indicate a clear advantage for either MGA or PGF as a means of enhancing the ovulation rate or embryo quality.

Journal Article↗
PubMed1998

Comparison of two estrus synchronization programs in a large, confinement-housed dairy herd.

OBJECTIVE: To compare pregnancy rates, seasonal effects, and economic benefits of 2 estrus synchronization programs for a confinement-housed dairy herd. DESIGN: Prospective cohort study. ANIMALS: 200 lactating Holstein cows. PROCEDURE: Cows eligible for breeding were palpated per rectum and randomly assigned to 2 treatment groups during 4 seasonal periods. Cows in one group (Ovsynch) received injections of gonadotropin releasing hormone (GnRH) on day 0, prostaglandin F2 alpha on day 7, and a second injection of GnRH on day 8. Cows in the other group (PP) that had a palpable corpus luteum were given prostaglandin F2 alpha. Estrus detection was not performed on the Ovsynch cows, which were artificially inseminated at a predetermined time after the second GnRH injection. Cows in the PP group were observed for signs of estrus, and only those that were detected in estrus were inseminated. RESULTS: Pregnancy rates and insemination rates were significantly improved for cows in the Ovsynch group, compared with cows in the PP group. CLINICAL IMPLICATIONS: The Ovsynch program was an economically advantageous method for controlling reproduction that resulted in pregnancies without the need for estrus detection.

Animal Husbandry↗
PubMed1998

Influence of flushing on LH secretion, follicular growth and the response to estrus synchronization treatment in suckled beef cows.

The effects of energy supplementation (flushing) on LH and estradiol secretion, follicular growth and the response to estrus synchronization treatment (Norgestomet + PMSG initiated 41.9 +/- 3.4 d after calving) were investigated in 16 suckled beef cows fed either 70% (Group C, n = 8) of energy requirements from calving to 3 wk after AI or fed the same restricted diet until 11 d before synchronization and then were supplemented with 2 kg concentrate until 3 wk after AI (Group S, n = 8). Concentrations of LH and estradiol 17 beta were measured from 3 sampling periods: 25 and 39 d after calving and between 29 and 49 h after implant removal. Ovaries were examined by ultrasonography 11 d before treatment to implant withdrawal (IR). The effects of energy level, day (or hour) of observation and corresponding interactions were tested on repeated measurements by split-plot ANOVA. No positive effect of flushing was observed on characteristics of LH secretion on Day 39. However, the size of the largest follicle and the number of large follicles were higher in Group S than in Group C cows, respectively, 7 and 9 d after the beginning of flushing to 2 d after the start of treatment. After IR, the estradiol secretion tended to be higher in Group S than in Group C cows (9.8 +/- 0.4 pg/mL vs 7.2 +/- 0.2 pg/mL; P = 0.06), but no effect on LH secretion was observed. After implant removal 12 cows ovulated (Group S: 7/8 vs Group C: 5/8; P > 0.05), 7 were pregnant at 21 d after AI (Group S: 6/8 vs Group C: 1/8; P < 0.05) and 4 at 45 d after AI (Group S: 4/8 vs Group C 0/8; P > 0.05). To conclude, flushing had a positive effect on follicular growth, which does not seem to be mediated by LH. In cows fed a restricted diet, flushing enhanced follicular growth, increased the fertilization rate and/or reduced early embryonic death.

Animals↗
PubMed1996

Detection of estrus by visual observation and radiotelemetry in peripubertal, estrus-synchronized beef heifers.

The effectiveness of two estrus-detection methods (visual observation and radiotelemetric, pressure-sensitive, rump-mounted devices) was compared in peripubertal, crossbred yearling beef heifers. Heifers (n = 50) were fitted with a pressure-sensitive device affixed to their rumps to which a battery-operated radio transmitter was connected. Activation of the sensor sent a radiotelemetric signal to a microcomputer via a fixed radio antenna. Heifer identification, date, time, and duration of standing events were recorded. Estrus was synchronized by feeding melengestrol acetate (MGA) for 14 d and then injecting PGF2 alpha 17 d after the last daily dose of MGA. Following the injection of PGF2 alpha, heifers were observed visually for signs of estrus at 0730 and 1630 (45 min each). Estrus was detected in 41 of 49 heifers (one lost the device) by visual observation and(or) the radiotelemetric device. Number of standing events during estrus, determined by the radiotelemetric device, averaged 50.1 +/- 6.4 per heifer, with the duration of estrus ranging from 2.6 to 26.2 h (average = 14 +/- .8 h). Visual observation failed to detect 11 of 41 heifers (37%) that were detected by the radiotelemetric device. Heifers with fewer standing events (19.3 vs 60.5; P < .001) and estrus of shorter duration (8.4 vs 15.6 h; P < .001) were those not identified by visual observation. Based on intervals between the first detected standing event of estrus and time of insemination, a wide window of fertility seems to exist in some heifers. Radiotelemetric devices were useful in identifying a greater (P < .05) proportion (100%) of heifers in estrus (increased efficiency) compared with visual observation (73%). However, accuracy of both methods was similar.

Animals↗
PubMed2003

Estrus synchronization in beef cows: comparison between GnRH+PGF2alpha+GnRH and PRID+PGF2alpha+eCG.

The aim of this study was to compare two protocols for estrus synchronization in suckled beef cows over a 2 years period. The population studied consisted of 172 Charolais and 168 Limousin cows from 12 and 14 beef herds, respectively. In each herd, cows were allotted to groups according to parity, body condition score and calving difficulty. Cows in Group 1 (n=174) received PRID on Day-8 with estradiol benzoate (10mg, vaginal capsule), dinoprost on Day-4 (25mg i.m.), eCG on Day 2 (500 IU i.m.). The PRID was removed on Day-2 and cows were inseminated on Day 0, 56 h after PRID was removed. Cows in Group 2 (n=166) received GnRH on Day-10 (100 microg i.m.), dinoprost on Day-3 (25mg i.m.) and GnRH on Day-1 (100 microg i.m.), and were inseminated on Day 0, 16-24h after the last GnRH treatment. Plasma progesterone concentrations were measured to determine cyclicity prior to treatment (Days-20 and -10), to confirm the occurrence of ovulation (Days 0 and 10) and to determine the apparent early pregnancy rate (Days 0, 10 and 24). Pregnancy diagnosis was performed by ultrasonography between Days 35 and 45. The effects of various factors on ovulation, apparent early pregnancy and pregnancy rates were studied using logistic mixed models. There was no significant difference between Groups 1 and 2, respectively, for the cyclicity rate before treatment (80.5% versus 80.1%), for apparent pregnancy rate on Day 24 (62.1% versus 54.8%, P=0.09) and for pregnancy rate on Days 35-45 (53.8% versus 46.3%, P=0.16). Ovulation rate was higher (P<0.01) in Group 1 (90.8%) than in Group 2 (77.1%) and was affected by cyclicity prior to treatment in Group 2 but not in Group 1 (Group 1: 88.2% in anestrous cows versus 91.4% in cyclic cows; Group 2: 45.5% in anestrous cows versus 85.0% in cyclic cows, P interaction=0.05). Apparent pregnancy rates on Day 24 were influenced by the year of study (52.4% versus 68.8%, OR=2.12, P<0.01) and by the cyclicity before treatment (anestrous cows 46.3% versus cyclic cows 61.5%, OR=1.86, P<0.05). Pregnancy rates at 35-45 days were influenced by the year of study (44.2% versus 59.8%, OR=1.92, P<0.01). In conclusion, although pregnancy rates were similar for the two treatments, the combination of GnRH+PGF2alpha+GnRH in suckled beef cows induced a lower rate of ovulation than treatment with PRID+PGF2alpha, particularly in anestrous cows.

Animals↗
PubMed2004

Ovarian follicular dynamics and hormonal profiles in heifer and mixed-parity Mediterranean Italian buffaloes (Bubalus bubalis) following an estrus synchronization protocol.

The primary objective was to elucidate ovarian follicular dynamics and hormonal profiles in nulliparous heifer (HE; n = 11 ) and mixed-parity (MP; n=10 ) Mediterranean Italian water buffaloes (Bubalus bubalis) following an estrus synchronization protocol. Both groups received a progesterone releasing intravaginal device (PRID) implant for 10 days; a luteolytic dose of synthetic prostaglandin was given 7 days after PRID insertion. Daily ultrasound monitoring and collection of blood to determine plasma concentrations estradiol and progesterone started 1 day after PRID removal and lasted for 55 and 65 days in HE and MP buffaloes, respectively. Data analysis was restricted to the first 5 days after PRID removal and to one estrus cycle following induced ovulation. The HE buffaloes were not inseminated and only one ovulated within 5 days after PRID removal; the remainder ovulated between 8 and 48 days after PRID removal (except one in which ovulation was never detected). All HP buffaloes were inseminated 72, 96 and 120 h after PRID removal; seven buffaloes ovulated within 5 days after PRID removal and two were pregnant. Mean diameter of the largest follicle was significantly smaller in HE than MP buffaloes the first 4 days after PRID removal. There was a parity by time interaction ( P=0.0047 ) for plasma progesterone concentrations; progesterone was higher in HE than MP buffaloes 1 day after PRID removal, but the converse was true 2 days after PRID removal. After induced ovulation, HE buffaloes exhibited a one-wave ( n=5; length of cycle, 8-12 days), two-wave ( n=4; range: 20-26 days) or three-wave cycle ( n=1; 25 days). In contrast, all non-pregnant MP buffaloes ( n=8 ) had a two-wave cycle (range: 19-25 days). For buffaloes with two-wave cycles, the growth rate and diameter of the largest follicle was significantly smaller in HE than MP buffaloes for both the first follicular wave (1.3mm versus 1.7 mm per day and 10.5 mm versus 13.3 mm, respectively) and the second follicular wave (1.0 mm versus 1.3 mm per day and 11.0 mm versus 13.8 mm). In conclusion, there were many significant morphological and endocrine differences between HE and MP buffaloes.

Administration, Intravaginal↗
PubMed1991

Induction of synchronized estrus and fertility in anestrous ZebuxTaurus crossbred cows.

A major cause for reproductive failures in Zebu x Taurine crossbred cows is postpartum anestrus. Crossbred cows were diagnosed to be in postpartum anestrus by palpation per rectum of nonfunctional ovaries. To induce synchronized estrus, the cows were treated by placement of a progesterone releasing intravaginal device (PRID) for various number of days, together with a single administration of prostaglandin F2 alpha (PGF, 5 mg intravulvosubmucos), estradiol-17beta (E2, 1 mg i.m.) or pregnant mare serum gonadotrophin (PMSG, 500 IU i.m.). Administration of PRID for 7 d, and of E2 and PMSG on Day 6, significantly improved the degree of behavioral estrus manifestation compared to single PRID for 12 d or PRID for 7 d, and of PGF on Day 6. However, the treatment combination of PRID and PMSG alone was associated with higher (P<0.01) conception rate to 2 fixed time A.I. at induced estrus. The mean interval from treatment to conception was also shortest (P<0.01) for this group. These results suggest that administration of PRID for 7 d, and of PMSG on Day 6 is highly effective in achieving synchronized behavioural estrus, a near normal CR to fixed time A.I. and a shorter interval from treatment to conception in anestrus ZebuxTaurine crossbred cows under Indian field conditions.

Journal Article↗
PubMed2001

Efficacy of an intravaginal progesterone insert and an injection of PGF2alpha for synchronizing estrus and shortening the interval to pregnancy in postpartum beef cows, peripubertal beef heifers, and dairy heifers.

The objective was to test the efficacy of an intravaginal progesterone insert and injection of PGF2alpha for synchronizing estrus and shortening the interval to pregnancy in cattle. Cattle were assigned to one of three treatments before a 31-d breeding period that employed artificial insemination. Control cattle were not treated, and treated cattle were administered PGF2alpha or an intravaginal progesterone-releasing insert (CIDR) for 7 d and treated with PGF2alpha on d 6. The treatments were applied in one of three experiments that involved postpartum beef cows (Exp. 1; n = 851; 56+/-0.6 d postpartum), beef heifers (Exp. 2; n = 724; 442.5+/-2.8 d of age), and dairy heifers (Exp. 3; n = 260; 443.2+/-4.5 d of age). Luteal activity before treatment was determined for individual cattle based on blood progesterone concentrations. In Exp. 1, there was a greater incidence of estrus during the first 3 d of the breeding period in CIDR+PGF2alpha-treated cows compared with PGF2alpha-treated or control cows (15, 33, and 59% for control, PGF2alpha, and CIDR+PGF2alpha, respectively; P < 0.001). The improved estrous response led to an increase in pregnancy rate during the 3-d period (7, 22, and 36% for control, PGF2alpha, and CIDR+PGF2alpha, respectively; P < 0.001) and tended to improve pregnancy rate for the 31-d breeding period for cows treated with CIDR+PGF2alpha, (50, 55, and 58% for control, PGF2alpha, and CIDR+PGF2alpha, respectively, P = 0.10). Improvements in rates of estrus and pregnancy after CIDR+PGF2alpha, were also observed in beef heifers. Presence of luteal activity before the treatment period affected synchronization and pregnancy rates because anestrous cows (Exp. 1) or prepubertal heifers (Exp. 2) had lesser synchronization rates and pregnancy rates during the first 3 d of the breeding period as well as during the entire 31-d breeding period. The PGF2alpha, and CIDR+PGF2alpha but not the control treatments were evaluated in dairy heifers (Exp. 3). The CIDR+PGF2alpha-treated heifers had a greater incidence of estrus (84%) during the first 3 d of the breeding period compared with the PGF2alpha-treated heifers (57%), but pregnancy rates during the first 3 d or during the 31-d breeding period were not improved for CIDR+PGF2alpha compared with PGF2alpha-treated heifers. In summary, the concurrent treatment of CIDR and PGF2alpha improved synchronization rates relative to PGF2alpha alone or control. Improved estrus synchrony led to greater pregnancy rates for beef cows and beef heifers but failed to improve pregnancy rates for dairy heifers.

Administration, Intravaginal↗
PubMed1996

Estrus synchronization in cattle using estradiol, melengestrol acetate and PGF.

In Experiment 1, all cattle were fed MGA (0.5 mg/head/d) for 7 d (designated Days 0 to 6) and given PGF on Day 6. One-half were administered estradiol valerate (EV; 5 mg, im) on Day 0. At Location 1, a higher proportion (P < 0.005) of EV-treated heifers were detected in estrus and bred by AI between Days 7 and 13 than control heifers not receiving EV (27 of 33 versus 15 of 32), but the number of pregnancies (12 vs 10) was not significantly different. Eighty-three of 104 EV-treated and 89 of 106 control cows were inseminated, resulting in 50 and 45 pregnancies, respectively (not significant). At Location 2, cattle were similarly treated and exposed to bulls on Days 7 to 49. Fall pregnancy rate was higher (P < 0.015) for EV-treated than control heifers (44 of 48 vs 33 of 46), but was not significantly different for cows (22 of 26 vs 19 of 23). In Experiment 2, estradiol 17beta (E17beta; 5 mg, im) and progesterone (100 mg, im) were administered on Day 0 (instead of EV). In a third group (designated the PGF group), cattle were bred on Days 0 to 6, and PGF was administered on Day 6 to those not yet bred. For 213 cows, the percentage pregnant to a synchronized estrus was greater in the PGF group (72%) than in either the control group treated with MGA (49%; P = 0.005) or the group receiving MGA and E17beta (54%; P < 0.025). Fall pregnancy rates were 91, 89, and 96% for the 213 cows (not significant) and 89, 93, and 98% for 131 heifers (not significant) in the PGF, MGA and E17beta groups, respectively. In cattle without a functional CL, the average diameter of the largest follicle at Day 6 was 1 to 2 mm smaller in the E17beta + MGA group than in the MGA group (difference significant only in cows at Location 1). Combined for both locations, the synchronized pregnancy rate in heifers without a functional CL on Day 6 was higher (P < 0.05) in the E17beta + MGA group than in the MGA group (11 of 21, 52% versus 4 of 20, 20%). Estrogen treatment caused regression of ovarian follicles with emergence of a new follicular wave. Including estrogen in an estrus synchronization program utilizing MGA and PGF significantly increased fall pregnancy rate in heifers (at 1 location) and the synchronized pregnancy rate of heifers without a functional CL at the time of PGF treatment (combined for both locations).

Journal Article↗
PubMed2005

Influence of estrus synchronization of prepubertal gilts on embryo quality.

Synchronization and superovulation are commonly used to obtain large numbers of embryos for experimental and practical purposes. This study compared the number, quality, and in vitro development of embryos recovered from gilts following single or double estrus synchronization and superovulation. Prepubertal gilts from the single synchronization group were injected with 1500 I.U. PMSG and 1000 I.U. hCG 72 h later. The double synchronized group of gilts was treated with 750 I.U. PMSG and 500 I.U. hCG 72 h later. After 17 days, 1500 I.U. PMSG followed by 1000 I.U. hCG was administered. Five days after insemination embryos were recovered and cultured for 6 days. Both single and double hormonal stimulation schedules resulted in recovery of elevated numbers of embryos (28.4 and 23.4 vs. 11.3; p<0.01 and p<or=0.05, respectively) with a higher percentage of embryos classified as degenerated (39.2% and 43.1%, respectively) compared to the non-stimulated, control group (5.1%). The number of embryos destined for culture did not differ between the single and double synchronized groups. The highest percentage of hatched embryos was observed in the control group. In conclusion, the single synchronization and superovulation schedule is sufficient to obtain high numbers of embryos, however, both synchronization methods resulted in the recovery of considerable numbers of degenerated embryos. A higher number and percentage of hatched embryos after culture was found among embryos from the control group compared to gonadotropin-stimulated gilts.

Animals↗
PubMed2000

Estrus synchronization and pregnancy rates in beef cattle given CIDR-B, prostaglandin and estradiol, or GnRH.

Two experiments were conducted to determine estrous response and pregnancy rate in beef cattle given a controlled internal drug release (CIDR-B) device plus prostaglandin F2 alpha (PGF) at CIDR-B removal, and estradiol or gonadotropin releasing hormone (GnRH). In Experiment I, crossbred beef heifers received a CIDR-B device and 1 mg estradiol benzoate (EB), plus 100 mg progesterone (E + P group; n = 41), 100 micrograms gonadotropin releasing hormone (GnRH group; n = 42), or no further treatment (Control group; n = 42), on Day 0. On Day 7, CIDR-B devices were removed and heifers were treated with PGF. Heifers in the E + P group were given 1 mg EB, 24 h after PGF, and then inseminated 30 h later. Heifers in the GnRH group were given 100 micrograms GnRH, 54 h after PGF, and concurrently inseminated. Control heifers were inseminated 12 h after onset of estrus. The estrous rate was lower (P < 0.01) in the GnRH group (55%) than in either the E + P (100%) or Control (83%) groups. The mean interval from CIDR-B removal to estrus was shorter (P < 0.01) and less variable (P < 0.01) in the E + P group than in the GnRH or Control groups. Pregnancy rate in the E + P group (76%) was higher (P < 0.01) than in the GnRH (48%) or Control (38%) groups. In Experiment II, 84 cows were treated similarly to the E + P group in Experiment I. Cows received 100 mg progesterone and either 1 mg EB or 5 mg estradiol-17 beta (E-17 beta) on Day 0 and either 1 mg of EB or 1 mg of E-17 beta on Day 8 (24 h after CIDR-B removal), in a 2 x 2 factorial design, and were inseminated 30 h later. There were no differences among groups for estrous rates or conception rates. The mean interval from CIDR-B removal to estrus was 44.2 h, s = 11.2. Conception rates were 67%, 62%, 52%, and 71% in Groups E-17 beta/E-17 beta, E-17 beta/EB, EB/E-17 beta, and EB/EB, respectively. In cattle given a CIDR-B device and estradiol plus progesterone, treatment with either EB or E-17 beta effectively synchronized estrus and resulted in acceptable conception rates to fixed-time artificial insemination.

Animals↗
PubMed1998

Estrus synchronization with lower dose of PGF2 alpha and subsequent fertility in subestrous buffalo.

Two experiments were conducted to determine luteal regression, estrous response and fertility in buffalo receiving cloprostenol via 2 routes of administration. In Experiment 1, cyclic buffalo (n = 10) were assigned to 2 equal groups receiving either 500 micrograms i.m. cloprostenol (Estrumate, ICI) or 125 micrograms cloprostenol injected intravulvosubmucosal (ivsm) ipsilateral to the side of the corpus luteum (CL) on Day 11 of an induced estrous cycle. Serum progesterone (P4) concentrations were evaluated immediately before treatment and at 24, 48, 72, 96 and 120 h after PGF2 alpha administration. The decline in serum P4 concentrations was significantly different (P < 0.05) between groups up to 48 hrs after treatment. However, no significant difference (P > 0.05) was observed for the interval from treatment to the onset of estrus (94.9 +/- 10.7 vs 96.0 +/- 15.9 h) for 500 or 125 micrograms of cloprostenol groups, respectively. In Experiment 2, multiparous, lactating subestrous buffaloes (n = 137) were treated either with 125 micrograms ivsm cloprostenol or 500 micrograms i.m. cloprostenol (n = 28 vs 33, respectively) during peak breeding (September-February) or low breeding (March-August) season (n = 37 vs 39, respectively). Buffalo observed in estrus were inseminated twice with frozen-thawed semen at 12 and 22 h after the onset of estrus. Buffalo that failed to exhibit estrus were given a second equal dose of cloprostenol at an 11-d interval and underwent fixed-time insemination at 72 and 96 h. The interval to the onset of estrus was 85.0 +/- 4.4 vs 73.2 +/- 2.6 h during peak breeding and 96.1 +/- 2.6 vs 92.1 +/- 3.8 h during the low breeding season for buffalo treated with 125 and 500 micrograms cloprostenol, respectively. These intervals were different (P < 0.05) between seasons but not between treatments in the same season. Conception rates of 47.8 vs 53.1% during peak breeding and 23.5 vs 25.6% during low breeding season were also different (P < 0.05) between seasons but not between the treatments in the same season for buffalo treated with 125 and 500 micrograms cloprostenol, respectively. These results indicated that 125 micrograms ivsm and 500 micrograms i.m. cloprostenol were equally effective for synchronizing estrus in subestrous buffalo. No negative effect of a lower dose of cloprostenol was observed on estrus synchrony and subsequent fertility; however, season of treatment had a significant effect on conception rates.

Animals↗
PubMed1993

Copulatory behavior of sexually inexperienced male guinea pigs paired with synchronized estrus females.

The copulatory behavior in sexually inexperienced male guinea pigs aged 12 weeks was observed under dim red illumination. The synchronized estrus females, which were used for receptive females, received a subcutaneous implantation of progesterone-filled tubing for 2 weeks, followed by 0.5mg progesterone injection. Females given these treatment exhibited the lordosis behavior at 19:00 and 21:00 h on 4th day, and had ovulated by 09:00 h on 5th day after removal of implant. During a 2-hrs test session, standard measures of copulatory behavior were recorded. The ejaculation could be observed within the first 30 min in 6 of 7 males. The mounts, intromissions and ejaculation in male guinea pigs were shown in a lower frequency and longer latency than those of rats and hamsters.

Animals↗