Synchronization Regimen Research Articles

An update on estrus synchronization in goats: a minor species.

Estrus synchronization allows for parturition at suitable times to take advantage of niche markets, feed supplies, labor, and rising price trends. In the past, synchronization of estrus in goats has focused primarily on dairy goats to allow for optimal timing of milk production. However, recent interest in meat goat production has resulted in attempts to use dairy goat, sheep, and cattle synchronization regimens in meat goat management systems. Methods of synchronization have included techniques as simple as alteration of light patterns or manipulation of social inputs (i.e., the buck effect) and as complex as varying timed hormonal treatments combined with light alteration and the buck effect. The synchronization of estrus using timed hormonal treatments seems to be more convenient in many meat goat production situations. Examples of hormones used include melatonin, progestogens (administered orally, as an injection, or by using intravaginal releasing devices), gonadotropins/GnRH (or agonists), and PG alone or in combination. As is seen with sheep and cattle, breed and/or breed type, stage of production, and environmental effects can influence synchronization success in goats. The introduction of breeds developed in other countries for rapid growth, such as the Boer goat, and increased consumer and producer interest have added to the impetus for developing cost-efficient and highly effective estrus synchronization regimens. New research is being conducted and various synchronization methods are being attempted in goats, a minor species, and the objective of this paper is to review these efforts.

Serum Estradiol Levels after 4 Days of Ovarian Hyperstimulation in Oocyte Donors Are Predictive of Embryo Quality and Clinical Outcomes

Objective: To determine whether estradiol (E₂) levels after 4 days of ovarian hyperstimulation in leuprolide-downregulated cycles are predictive of embryo quality and pregnancy outcome in oocyte donation. Material and Methods: Retrospective analysis of 287 consecutive oocyte donation cycles performed at a university assisted reproduction therapy program between January 1996 and December 2000. Oocyte donors and recipients followed a non-varied standard synchronization regimen. A serum E₂ (day-5 E₂) was obtained from egg donors the morning after leuprolide acetate downregulation and 4 days after hMG/FSH administration. Day-5 E₂ was categorized into 3 groups: group I <75 pg/ml; group II 75–350 pg/ml, and group III ≧350 pg/ml. All embryo transfers were performed 3 days after oocyte recovery. Results: Elevated day-5 E₂ levels were directly correlated with higher average embryo scores, greater number of oocytes retrieved, and greater number of embryos available for transfer and cryopreservation. Improved pregnancy outcomes were also noted for group III (day-5 E₂ level >350 pg/ml). Conclusion: After 4 days of gonadotropin stimulation, an E₂ level of >350 pg/ml is most predictive of higher embryo grade and pregnancy outcome in oocyte donation.

19. Efficacy of oestrus synchronization regimens with PGF2α and progesterone in dairy heifers

19. Efficacy of oestrus synchronization regimens with PGF2α and progesterone in dairy heifers

Supraphysiological estradiol levels do not affect oocyte and embryo quality in oocyte donation cycles.

The study aim was to determine whether supraphysiological estradiol (E(2)) levels reduce oocyte/embryo quality in oocyte donation cycles. A retrospective analysis of 330 consecutive fresh oocyte donation cycles was performed in an assisted reproductive treatment programme between January 1996 and December 2000. Throughout the study period, oocyte donors and recipients followed a standard synchronization regimen that did not vary. A serum E(2) level (peak E(2)) was obtained from all oocyte donors on the morning of HCG administration. Peak E(2) values were grouped by 33rd percentile (group I, <1500 pg/ml; group II, 1500-3000 pg/ml; and group III, >3000 pg/ml). All embryo transfers were performed on day 3 after oocyte recovery. Comparisons between groups revealed no significant differences in the quality of oocytes retrieved, and in fertilization rates. Higher peak E(2) levels were directly correlated with a greater number of oocytes retrieved, embryos available for transfer and cryopreservation, and higher average embryo quality scores (P < 0.005). Compared with group I, group III had significantly higher embryo implantation rates (P < 0.05). Sustained supraphysiological E(2) levels do not adversely affect the quality of developing oocytes and embryos. On the contrary, elevated E(2) levels are associated with a larger number of oocytes and embryos and high-grade embryos for transfer/cryopreservation and, consequently, improved implantation rates.

The use of GnRH or estradiol to facilitate fixed-time insemination in an MGA-based synchronization regimen in beef cattle

Two experiments were conducted to compare pregnancy rates when GnRH or estradiol were given to synchronize ovarian follicular wave emergence and ovulation in an MGA-based estrus synchronization program. Crossbred beef cattle were fed melengestrol acetate (MGA, 0.5 mg per day) for 7 days (designated days 0–6, without regard to stage of the estrous cycle) and given cloprostenol (PGF; 500 μg intramuscular (im)) on day 7. In Experiment 1, lactating beef cows ( n=140) and pubertal heifers ( n=40) were randomly allocated to three groups to receive 100 μg gonadorelin (GnRH), 5 mg estradiol-17β and 100 mg progesterone (E+P) in canola oil or no treatment (control) on day 0. All cattle were observed for estrus every 12 h from 36 to 96 h after PGF. Cattle in the GnRH group that were detected in estrus 36 or 48 h after PGF were inseminated 12 h later; the remainder were given 100 μg GnRH im 72 h after PGF and concurrently inseminated. Cattle in the E+P group were randomly assigned to receive either 0.5 or 1.0 mg estradiol benzoate (EB) in 2 ml canola oil im 24 h after PGF and were inseminated 30 h later. Cattle in the control group were inseminated 12 h after the first detection of estrus; if not in estrus by 72 h after PGF, they were given 100 μg GnRH im and concurrently inseminated. In the absence of significant differences, all data for heifers and for cows were combined and the 0.5 and 1.0 mg EB groups were combined into a single estradiol group. Estrus rates were 57.6, 57.4 and 60.0% for the GnRH, E+P and control groups, respectively ( P=0.95). The mean (±S.D.) interval from PGF treatment to estrus was shorter ( P<0.001) and less variable ( P<0.001) in the E+P group (49.0±6.1 h) than in either the GnRH (64.2±15.9 h) or control (66.3±13.3 h) groups. Overall pregnancy rates were higher ( P<0.005) in the GnRH (57.6%) and E+P (55.7%) groups than in the control group (30.0%) as were pregnancy rates to fixed-time AI (47.5, 55.7 and 28.3%, respectively). In Experiment 2, 122 crossbred beef heifers were given either 100 μg GnRH or 2 mg EB and 50 mg progesterone in oil on day 0 and subsequently received either 100 μg GnRH 36 h after PGF and inseminated 14 h later or 1 mg EB im 24 h after PGF and inseminated 28 h later in a 2×2 factorial design. Pregnancy rates were not significantly different among groups (41.9, 32.2, 33.3 and 36.7% in GnRH/GnRH, GnRH/EB, EB/GnRH and EB/EB groups, respectively). In conclusion, GnRH or estradiol given to synchronize ovarian follicular wave emergence and ovulation in an MGA-based synchronization regimen resulted in acceptable pregnancy rates to fixed-time insemination.

Sincronização de estro e dinâmica folicular de éguas Crioulas submetidas a tratamentos com norgestomet, acetato de melengestrol e altrenogest

21 Crioulo mares on reproductive age were grouped into 3 groups (I, II e III) with 7 animals each; group I was treated with unique 3 mg norgestomet + 5 mg estradiol valerate intramuscular injection and a subcutaneous implant of norgestomet during 9 days; group II received unique 5 mg of 17-b estradiol intramuscular injection and 0,5 mg of melengestrol acetate given orally during 9 days; group III consisted on mares given 0,045 mg/kg altrenogest orally during 9 days. At progestogen treatment removal (9th. day), all mares from the 3 groups received luteolytic dose of luprosteol and 3.000 UI of hCG when dominant follicle was ultrasonographically detected in ovulatory conditions . All mares were daily evaluated by rectal palpation and ultrasound examination for retrospectively measurement of the largest and second largest follicles, and mated by tested stallions closed to ovulation. Follicular development was not observed on group II (MGA). Considering 5 days post PGF2a-analogue administration, synchronization rates for groups I and III were, respectively, 85.71% and 66.70% (p > 0.05). Porcentage of oestrus supression for these groups were, respectively, 85.71% and 100.00% (p > 0.05). Pregnancy rate was not significantly different between the two groups (I, 100% and II, 85.71%; p > 0.05). Results were based on mares showing response to the synchronization regimen. PGF2a-oestrus, PGF2a-hCG, hCG-ovulation and PGF2a-ovulation intervals for groups I and III were 4.5 ± 0.80 and 4.2 ± 0.8 (p > 0.05), 8.0 ± 1.41 and 6.17 ± 0.6 (p > 0.05), 1.5 ± 0.22 and 2.28 ± 0.28 (p > 0.05) and 9,8 ± 1,02 and 8,6 ± 1,32 (p > 0.05) days respectively. The results prove the eficiency of oestrus synchronization regimens by norgestomet implant and oral administration of altrenogest, with tendency to higher synchronization rate to norgestomet system, although no significantly diferences were observed concerning to reproductive parameters and follicular dynamics data, with exception to the minor largest diameter of dominant follicles and ocurrence of only one major wave for supressed cycles by progestogen-estradiol regimen.

Effect of crestar ™ on estrus synchronization and the relationship between fecal and plasma concentrations of progestagens in buffalo cows

In buffaloes estrus synchronization provides an opportunity for enhanced use of AI; however, changes in hormone secretion during synchronization are poorly understood. The aim of this investigation was to determine if the concentration of progesterone metabolites in feces would correlate with the concentration of progesterone in blood and thus, could be used for noninvasive monitoring of the reproductive status in buffalo cows. Additionally, the influence of a norgestomet-estradiol treatment (CRESTAR ™-ear implant) was investigated. According to the clinical examination and the progesterone profile in blood samples during the three wks before the treatment, the 17 animals were allotted to 3 groups: 1) CL = presence of corpus luteum throughout the period of 3 wks before the treatment (n = 8); 2) CY = cyclic, corpus luteum present for less than 3 wks (n = 6); and 3) AE = anestrous, with inactive ovaries (n = 3). In the first group, 4 animals started an estrous cycle after implant withdrawal and conceived after natural mating. In the second group one of the cyclic cows showed estrus two d after implant withdrawal, the other 3 had a delayed estrus (12 to 16 d). The two cows which had had inactive ovaries at the beginning but were cyclic before the treatment started, remained cyclic after implant withdrawal but did not become pregnant. The 3 anestrous cows of the third group remained anestrous after the treatment. The progesterone concentration in blood clearly correlated with the concentration of the metabolites in feces. Therefore, this noninvasive method is a valuable tool for determining the luteal status, and such information may be useful for developing estrus synchronization regimens in buffalo cows.

HuR regulates cyclin A and cyclin B1 mRNA stability during cell proliferation.

Colorectal carcinoma RKO cells expressing reduced levels of the RNA-binding protein HuR (ASHuR) displayed markedly reduced growth. In synchronous RKO populations, HuR was almost exclusively nuclear during early G(1), increasing in the cytoplasm during late G(1), S and G(2). The expression and half-life of mRNAs encoding cyclins A and B1 similarly increased during S and G(2), then declined, indicating that mRNA stabilization contributed to their cell cycle-regulated expression. In gel-shift assays using radiolabeled cyclin RNA transcripts and RKO protein extracts, only those transcripts corresponding to the 3'-untranslated regions of cyclins A and B1 formed RNA-protein complexes in a cell cycle-dependent fashion. HuR directly bound mRNAs encoding cyclins A and B1, as anti-HuR antibodies supershifted such RNA-protein complexes. Importantly, the expression and half-life of mRNAs encoding cyclins A and B1 were reduced in ASHuR RKO cells. Our results indicate that HuR may play a critical role in cell proliferation, at least in part by mediating cell cycle-dependent stabilization of mRNAs encoding cyclins A and B1.

Effect of concomitant injection of prostaglandin and PMSG on pregnancy rate and prolificacy of artificially inseminated Spanish goats synchronized with controlled internal drug release devices

Controlled internal drug release (CIDR) devices containing progesterone were used for 16 days to synchronize estrus in 108 mature Spanish does in the natural breeding season. Pregnant mare serum gonadotrophin (PMSG, 250 IU) was given to all does 48 h prior to CIDR removal. At the time of treatment with PMSG, a random half of the does received prostaglandin (PGF, 5 mg dinoprost tromethamine, Lutalyse) to determine the effect of its addition on pregnancy rates and prolificacy in artificially inseminated does. Mean pregnancy rates, 64.5% and 59.5%, and prolificacy, 170% and 166%, were not significantly different ( P>0.05) for does treated with PMSG or PMSG/PGF, respectively. Administering PGF to does on this synchronization regimen in the natural breeding season is unwarranted.

Synchronization of estrus with PGF 2α administered 18 days after a progesterone treatment in lactating dairy cows

In a previous study we showed that estrus synchronization with 2 treatments of PGF 2α 13 d apart reduced conception rate at the synchronized estrus and that this reduction occurred mainly in cows in the early luteal phase at the second PGF 2α treatment. The objective of the present study was to determine the efficacy of a synchronization regimen in which PGF 2α was administered during the mid- to late-luteal phase to cows that had previously been synchronized with progesterone. Spring-calving cows from 6 dairy herds were used in this study. On Day −32 (Day 1 = the start of the breeding season), cows that had calved 2 or more weeks ago were randomly assigned to a synchronization (S, n = 732) or control (C, n = 731) group. Cows in Group S were treated with an intravaginal progesterone device (CIDR) for 12 d from Day −32 to Day −20, while those in Group C were left untreated. Similar percentages of cows in Group S (80.6%) and C (82.9%) had cycled by Day −7. The CIDR treatment synchronized the onset of estrus, resulting in 92.9% of cows in estrus being detected within 7 d after CIDR removal. Cows in Group S that had cycled by Day −7 were treated with PGF 2α (25 mg, im, Lutalyse) on Day −2. Cows in both groups that were anestrous on Day −7 were treated with a combination of progesterone and estradiol benzoate (EB) to induce estrus and ovulation (CIDR and a 10 mg EB capsule on Day −7, CIDR removal on Day −2, and injection of 1 mg EB 48 h after CIDR removal). The PGF 2α treatment synchronized the onset of estrus in 87.5% of the cows. Group S and C cows had similar conception rates to first (61.0 vs 58.3%) and second (58.4 vs 60.9%) AI; similar pregnancy rates over the AI period (82.8 vs 79.2%) and over the whole breeding season (91.9 vs 90.6%); and required a similar number of services per pregnancy to AI (1.7 vs 1.8). The interval from the start of the breeding season to conception for cows conceiving to AI or to combined AI and natural mating was shorter (P < 0.001) by 5.7 and 6.2 d, respectively, for the Group S cows. It is concluded that the treatment regimen tested in the present study achieved satisfactory estrus synchronization, had no detrimental effect on fertility at the synchronized estrus, and shortened the interval from start of the breeding season to conception.

Reproductive performance of lactating dairy cows following estrus synchronization regimens with PGF2α and progesterone

The objective of this study was to evaluate the reproductive performance of lactating cows in seasonal dairy herds after estrus synchronization with PGF2α (PG) with or without supplementation with progesterone (P4). In Trial 1, synchronized cows (S1; n = 521) were compared with untreated control cows (C; n = 518) in 5 herds. Estrus of cows in the S1 group was synchronized with 2 treatments of PG (Lutalyse) 13 d apart. The breeding season started 2 d after the second PG. Cows were first bred by AI for 7 wk and then herd sires were used. Compared with C cows, estrus synchronization in the treated cows reduced the conception rate to first AI (61.1 vs 70.5%; P < 0.01) and the intervals from start of the breeding season to conception for cows conceiving to AI (11.0 vs 14.6 d; P < 0.05) or to both AI and natural mating (16.5 vs 18.4 d; P < 0.05). There was no effect on conception rate to second AI (68.8%), on pregnancy rate by Day 24 (72.3%) or Day 49 (86.3%) of the breeding season, or on the percentage of cows not pregnant at end of the breeding season (5.0%). In Trial 2, effects of P4 supplementation before the second PG on reproductive performance were evaluated in 4 herds. Estrus of each cyclic cow was synchronized with PG as in Trial 1. Half of the cows in each herd were treated with an intravaginal P4 device (CIDR) for 5 d before the second PG (S2+P4, n = 608), whereas the remaining half received no CIDR treatment (S2, n = 593). Compared with S2 cows, P4 treatment increased the estrous response rate to the second PG (89.6 vs 82.9%; P < 0.01), the conception rate to first AI (65.1 vs 59.7%; P = 0.07), the pregnancy rate by Day 6 of the breeding season (59.3 vs 49.0%; P < 0.001), and reduced the intervals from start of the breeding season to conception for cows conceiving to AI (8.6 vs 10.4 d; P < 0.10) or to both AI and natural mating (12.7 vs 16.4 d; P < 0.01). Treatment with a used CIDR from Days 16 to 21 after start of breeding to resynchronize returns to service had no effect on conception rate to first or second AI but may decrease the conception rate to second AI in cows previously treated with CIDR. In conclusion, estrus synchronization with the double PG system can reduce fertility, while P4 supplementation for 5 d before the second PG can improve estrous response and overall reproductive performance. Stage of the estrous cycle at the time of the second PG can affect fertility following synchronization.

Induction Chemotherapy with Versus Without Hormonal Synchronisation in Locally Advanced Breast Cancer

Sixty-nine patients with locally advanced breast cancer were given induction chemotherapy with doxorubicin and cyclophosphamide (day 1) followed by methotrexate and 5-Fu (day 8). Thirty-two of these patients were also given tamoxifen (days 2-6) in an attempt to induce a Gl arrest in cancer cells, and oestrogen (days 7-8) to stimulate proliferation and thus induce a synchronized wave of proliferating cells. The induction therapy response rate was 61% in the series as a whole (n = 69), but was found to be significantly better in the group on the tamoxifen/oestrogen synchronization regimen than in the remainder on chemotherapy alone (82% vs. 43%). This difference was particularly marked in the respective receptor-positive subgroups [90% (9/10) vs. 30% (3/10); p< 0.001]. The findings suggest that, in combination with chemotherapy, tamoxifen/oestrogen therapy, given in the sequence outlined here, constitutes a promising regimen for the treatment of locally advanced receptor-positive breast cancer patients.

Influence of the synchronization treatment on the superovulatory response of Murciana goats

This study was undertaken to determine if the synchronization treatment that accompanies superovulation in goats affected the ovulatory response and the incidence of premature regressive corpora lutea. Twenty eight Murciana goats were submitted, once in autumn and once in spring, to one of three different synchronization regimens based on fluorogestone acetate (FGA) sponges: treatment A, the standard short synchronization system; treatment B, the standard long synchronization system and treatment C, similar to treatment B, but with prostaglandin F 2α injected two days before pessary removal. All animals were superovulated with 16 mg of follicle stimulating hormone (FSH). No difference in the percentage of animals with regressed corpora lutea was found due to season (27% in fall vs. 44% in spring, P = 0.196), due to the length of FGA treatment (41% with treatment A vs. 31% in treatment C, P = 0.55), or due to the effect of prostaglandin F 2α administration (33% in treatment B vs. 31% in treatment C, P = 0.89). The number of corpora lutea present at the time of embryo recovery did not differ among treatments ( P > 0.05) or seasons ( P > 0.05), but embryo recovery was lower ( P < 0.001) in animals with regressed corpora lutea (1.2 ± 0.6) than in animals with apparently normal luteal structures (8.9 ± 0.9). These data show that the synchronization regimen does not interfere with the superovulatory response and that high percentages of premature luteal regression can be associated with FSH-based superovulatory regimes. In the same way, it can be concluded that the administration of prostaglandin F 2α does not increase the number of animals showing premature luteal regression.

Endocrine and behavioral events of estrous cyclicity and synchronization in wood bison ( [formula omitted

This study was designed to noninvasively characterize estrous cycles and evaluate the effectiveness of estrous cycle synchronization protocols in wood bison. Daily urine and fecal samples and behavioral observations were collected over 2 breeding seasons from a captive herd of 18 adult, female wood bison. All samples were analyzed by enzymeimmunoassay for pregnanediol-glucuronide (PdG: urine) or progesterone (P 4: feces). In Year 1, animals were divided into 3 treatment groups: 1) natural estrous controls, n = 6; 2) PG, 2 injections of cloprostenol, 11 d apart, n = 6; 3) SMB, Syncro-Mate-B implants left in place for 9 d with an estradiol valerate injection at the time of implantation, n = 6. In Year 2, control animals remained the same and synchronization regimens were repeated, but with each animal receiving alternate treatments. In both years, 11 d after treatment cessation, females were subjected to ultrasound examination to evaluate ovarian activity. Combined endocrine and behavioral data from natural estrous cycles demonstrated seasonal effects, with mean cycle lengths of 20.8 ± 0.3, 21.5 ± 0.5 and 21.1 ± 0.4 d, based on behaviors, PdG and P 4 respectively. Females which demonstrated behavioral estrus did so within 4 (SMB, 11 12 ) or 5 (PG, 10 12 ) days after treatment. The SMB-treated animals exhibited estrous behavior within a 3-d span, with 55% exhibiting estrus 3 d after treatment ended, while the onset of estrus in PG-treated animals occurred over 4 d, with only 40% occurring on a single day. At the second estrus, 77% of SMB-treated animals and 74% of PG-animals demonstrated estrous behavior within 4 d, while at the third estrus, 88 and 90% of treated animals showed estrous behavior within 3 or 4 d, respectively. Ultrasound assessment revealed that only 50% ( 12 24 ) of treated animals possessed corpora lutea (CL), 67% in PG-treated females and 33% in SMB-animals. The total number of CL tended to be greater in PG- (10) than in SMB-(5) treated animals. Females with no CL demonstrated attenuated progestin profiles compared to those with ovulations. Additionally, a total of 28 follicles was detected, with a greater proportion (P < 0.05) from SMB-treated animals (78.5%) than from those receiving PG (25%). These results indicate that wood bison estrous cycles and synchronization can be monitored using either urine or feces. However, ovulation and normal luteal function did not occur at the first estrus after synchronization, perhaps due to stressors associated with capture and restraint.

Synchronization of estrus in yearling beef heifers with the melengestrol acetate/prostaglandin F 2α system: Efficiency of timed insemination 72 hours after prostaglandin treatment

Two experiments were conducted to determine the conception rates of heifers time-inseminated following melengestrol acetate/prostaglandin F 2α (MGA/PG) estrous synchronization treatment. In Experiment 1, timed insemination of heifers at 72 h after the PG injection, without regard for behavioral estrus, tended to improve (P < 0.15) the percentage of heifers pregnant to artificial insemination (AI) compared with that of synchronized heifers bred 12 h after they were first detected in estrus. In the timed-insemination treatment, heifers exhibiting behavioral estrus 48 to 72 h after PG tended to have an increased (P < 0.15) conception rate to AI compared with heifers exhibiting estrus within 48 h of PG administration. In Experiment 2, the number of heifers conceiving to AI following the MGA/PG estrous synchronization regimen was increased by mass insemination of all heifers not exhibiting estrus by 72 h after PG. The pregnancy rate to AI was higher in heifers with serum progesterone (P 4) concentrations higher than 1 ng/ml compared with that of heifers with concentrations lower than 1 ng/ml. Of heifers with serum P 4 greater than 1 ng/ml, the pregnancy rate to AI tended to be higher when concentrations exceeded 2 ng/ml than when concentrations were 1 to 2 ng/ml. In cyclic heifers, timed insemination can increase the percentage of heifers pregnant after being synchronized with MGA/PG.

Endocrine and behavioral events of estrous cyclicity and synchronization in wood bison ( [formula omitted

Abstract This study was designed to noninvasively characterize estrous cycles and evaluate the effectiveness of estrous cycle synchronization protocols in wood bison. Daily urine and fecal samples and behavioral observations were collected over 2 breeding seasons from a captive herd of 18 adult, female wood bison. All samples were analyzed by enzymeimmunoassay for pregnanediol-glucuronide (PdG: urine) or progesterone (P4: feces). In Year 1, animals were divided into 3 treatment groups: 1) natural estrous controls, n = 6; 2) PG, 2 injections of cloprostenol, 11 d apart, n = 6; 3) SMB, Syncro-Mate-B implants left in place for 9 d with an estradiol valerate injection at the time of implantation, n = 6. In Year 2, control animals remained the same and synchronization regimens were repeated, but with each animal receiving alternate treatments. In both years, 11 d after treatment cessation, females were subjected to ultrasound examination to evaluate ovarian activity. Combined endocrine and behavioral data from natural estrous cycles demonstrated seasonal effects, with mean cycle lengths of 20.8 ± 0.3, 21.5 ± 0.5 and 21.1 ± 0.4 d, based on behaviors, PdG and P4 respectively. Females which demonstrated behavioral estrus did so within 4 (SMB, 11 12 ) or 5 (PG, 10 12 ) days after treatment. The SMB-treated animals exhibited estrous behavior within a 3-d span, with 55% exhibiting estrus 3 d after treatment ended, while the onset of estrus in PG-treated animals occurred over 4 d, with only 40% occurring on a single day. At the second estrus, 77% of SMB-treated animals and 74% of PG-animals demonstrated estrous behavior within 4 d, while at the third estrus, 88 and 90% of treated animals showed estrous behavior within 3 or 4 d, respectively. Ultrasound assessment revealed that only 50% ( 12 24 ) of treated animals possessed corpora lutea (CL), 67% in PG-treated females and 33% in SMB-animals. The total number of CL tended to be greater in PG- (10) than in SMB-(5) treated animals. Females with no CL demonstrated attenuated progestin profiles compared to those with ovulations. Additionally, a total of 28 follicles was detected, with a greater proportion (P

Evidence for the action of bovine follicular fluid factor(s) other than inhibin in suppressing follicular development and delaying oestrus in heifers.

The aim of this study was to investigate the importance of inhibin in the delay in return to oestrus in heifers induced by steroid-stripped bovine follicular fluid (bFF). Oestrous activity was synchronized in 18 Hereford x Friesian heifers with two injections of prostaglandin (PG) 12 days apart. At the time of the second PG injection (time 0), the animals were assigned at random to one of three experimental groups and received i.v. injections of 20 ml saline (controls, n = 6), whole bFF (FF group, n = 6) or bFF in which the bioactive inhibin content had been reduced by > 95% by immunoaffinity chromatography (-INH group, n = 6; inhibin content approximately 0.8 ml whole bFF) every 8 h for 2 days. In a dose-response study, 2.5 ml whole bFF was insufficient to delay oestrus consistently following a similar synchronization regimen. Blood samples were taken every 8 h, initially before each injection and then subsequently for a further 9 days for hormone analysis. Animals were observed every 8 h throughout the experiment for signs of behavioural oestrus. The ovaries of all animals were examined using real-time ultrasonography about 30 h after the second PG injection. Treatment failed to suppress peripheral follicle-stimulating hormone (FSH) concentrations, although a significant increase was observed in both treatment groups after cessation of injections. Progesterone concentrations fell immediately after the second PG injection in all animals and remained below minimum detectable concentrations in all treated animals for the remainder of the experiment. In control animals, progesterone rose above minimum detectable concentrations by day 6 and continued to rise until the end of the experiment. Analysis of samples taken from treated animals several days after observed oestrus revealed that all had apparently ovulated. Mean daily luteinizing hormone (LH) concentrations did not differ between treatment groups before ovulation, but after ovulation, mean daily LH was significantly reduced in control animals as progesterone concentrations rose. Follicular development, as assessed by the mean antral diameter of the largest follicle on a pair of ovaries at ultrasound examination, was significantly suppressed in treated animals compared with controls (P < 0.01) and there was no significant difference (P = 0.397) between the two treatment groups. Control animals displayed oestrus 68 h (+/- 8 SEM) after the second PG injection, but oestrus was delayed in treated animals to 186h +/- 5 (FF group) and 191 h +/- 6 (-INH group).

Evaluation of three estrus synchronization regimens for use in extensively managed [formula omitted] and [formula omitted]/ [formula omitted] heifers in Northern Australia

Two herds of extensively managed yearling Bos indicus and Bos indicus × Bos taurus heifers (n = 169) were assigned to one of three estrus synchronization treatment groups. The treatments consisted of 1) two injections of the prostaglandin (F 2α) analogue, luprostiol (7.5 mg), given 12-d apart; 2) insertion of an intravaginal progesterone-releasing device (CIDR-B), followed by 400 IU i.m. pregnant mare serum gonadotrophin (PMSG) and 7.5 mg luprostinol at CIDR-B removal or 3) subcutaneous progestagen implant (SMB) for 10-d, followed by 400 IU i.m. and 7.5 mg i.m. luprostiol at implant removal. A dual tail paint-raddle system was used to evaluate response to treatment. Each treatment group was inseminated according to the manufacturer's recommendations for fixed-time artificial insemination (A.I.; luprostiol, 72h after the second injection, SMB and CIDR-B 48h after implant/device removal). The overall 51-d pregnancy rates for the three treatments were 18.6% (luprostiol), 48.8% (CIDR-B), and 53.3% (SMB). There were significant differences in the pregnancy rate between CIDR-B and luprostiol (P = 0.004) and between SMB and luprostiol (P =< 0.0001), but there was no difference in pregnancy rate between CIDR-B and SMB treatment.

Synchronization of estrus in beef cows and heifers with prostaglandin F 2α and estradiol benzoate

An experiment was conducted to study an estrous synchronization regimen that involved the use of prostaglandin F 2α (PGF 2α) alone or in combination with estradiol benzoate (EB) and appointment breeding. Fifty-three registered Angus yearling heifers and 167 registered Angus cows (3 to 9 yr of age) were given two injections of PGF 2α 11 d apart. Forty-eight hours after the second injection of PGF 2α′ a random sample consisting of 117 cows and heifers was injected with EB in sesame seed oil. All females in the herd were artificially inseminated 80 h after the second injection of PGF 2α. Nearly equal percentages (25.1 vs 25.6%; P = 0.93) of treated (EB) and control (no EB) females conceived at the appointment breeding. Use of EB tended to reduce (P = 0.06) natural service conception rate (83.4 vs 93.1% for EB and control groups, respectively). Estrous synchronization treatment did not affect interval from Day 1 of the breeding season to calving.

Insemination management for a one-injection prostaglandin F 2α synchronization regimen. I. One daily insemination period versus use of the a.m./p.m. rule

Following detection of estrus in a one-injection prostaglandin F 2α (PGF 2α) synchronization regimen, 261 dairy heifers were randomly inseminated (A.I.) either once between 0800 and 0900 h daily (a.m.) or about 12 h after detection of estrus (a.m./p.m.). During the regimen, 31.8 and 33.3% for the a.m./p.m. and a.m. groups, respectively showed estrus and received A.I. during the pre-PGF 2α period. The remaining heifers were injected with PGF 2α with 95.6% from a.m./p.m. and 96.5% from a.m. showing estrus and receiving A.I. within five days after PGF 2α. Pregnancy rates of 62.9% for a.m./p.m. and 62.0% for a.m. did not differ. Progesterone at the time of injection was similar between groups and was not correlated with either response to PGF 2α or fertility. Percentages of heifers in estrus <24, 25–48, 49–72, 73–96 and >96 after PGF 2α were 4.7, 30.2, 45.6, 14.3 and 5.3, respectively, with a mean time of 61.0±1.9 h. Satisfactory conception rate was attained with a.m. insemination.