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1.
Induction of ovulation for timed artificial insemination (TAI) with the Ovsynch protocol was evaluated in 49 anoestrous and lactating Bos taurus x Bos indicus cows. Palpation per rectum and transrectal ultrasonography were used on Days -30, -20, -10 and 0 (start of treatment) to confirm anoestrus but with the presence of follicles > or = 10 mm, and every other day during treatment to determine ovarian activity. Cows were randomly assigned to: (1) Ovsynch (n = 24; Day 0, 200 microg GnRH; Day 7, 150 microg PGF2alpha; Day 9, 200 microg GnRH + TAI 16 to 20 h later) and (2) control (n = 25; no treatment). Rates of ovulation for the first GnRH injection, detection of a corpus luteum (CL) at PGF2alpha injection, pregnancy and induction of cyclicity were greater (P < 0.05) with Ovsynch. There was no effect of body condition score (P > 0.05). In conclusion, the Ovsynch protocol was not effective in obtaining acceptable pregnancy rate for TAI, but it was effective for induction of cyclicity in anoestrous and lactating Bos taurus x Bos indicus cows under tropical conditions.  相似文献   

2.
Reproductive performance of two types of timed artificial insemination (TAI) protocols with or without intravaginal progesterone insert (CIDR) was investigated in a commercial herd of Holstein heifers. A total of seventy-four heifers with 14.4 months of age were allocated to two groups; Ovsynch (n=44) and estradiol benzoate (EB) used Heatsynch (EB-Heatsynch, n=30), and each group was additionally divided into two subgroups with CIDR insertion from day 0 to 7 (n=36) and without CIDR group (n=38). Blood was collected for progesterone (P4) analysis and ovarian finding was monitored with ultrasonography. Heifers in CIDR-treated group resulted in higher pregnancy rate as compared to No-CIDR-treated group (63.9% vs 21.1%, P<0.01). Heifers with functional corpus luteum (CL) on day 0 resulted in significantly higher pregnancy rate in CIDR-treated group than No-CIDR-treated group (day 0: 67.9% vs 13.0%, P<0.01). CIDR insertion suppressed the intermediate ovulation during the first 7 days and the period from the second GnRH or EB administration to TAI as compared to No-CIDR-treated group (first 7 days: 33.3% vs. 52.6%; P<0.05, before TAI: 11.1% vs. 37.0%; P<0.05). In conclusion, the selected TAI protocols with CIDR provided acceptable pregnancy rate and contributed to the economical improvement by shortening the average age of first calving approximately for 2.5 months as compared to the previous management without TAI protocols.  相似文献   

3.
Recently, reproductive management has become more difficult as a result of increased herd size. Problems with missing estrous signs and decrease in conception rate by artificial insemination (AI) performed at wrong timing have caused low AI conception rates. In 1995, ovulation synchronization and fixed-time AI (Ovsynch/TAI) was developed in the USA as a new reproductive technology, which was accepted as an useful reproductive management tool in many countries. However, no information on the use of Ovsynch/TAI was available in Japan. It was, therefore, warranted to show the ovulation rate and conception rate after Ovsynch/TAI using gonadotropin releasing hormone analogue (GnRH-A, fertirelin acetate) and prostaglandin F2alpha (PGF2alpha)-THAM, both were commercially available in this country. The conception rate after Ovsynch/TAI has been known to vary among different herds and individuals. Investigation and analysis of factors affecting the conception rate was also warranted to improve the conception rate. A series of experiments were carried out to establish Ovsynch/TAI using domestically produced GnRH-A and PGF2alpha and to study factors affecting conception rate after Ovsynch protocol. Ovsynch using 100 microg GnRH-A and 25 mg PGF2alpha were observed using ultrasonography. As a result, a high synchronization rate of ovulation at 16 to 20 h after the second GnRH injection was confirmed. The conception rate after Ovsynch/TAI was compared in 87 cows with the conception rate after AI at estrus induced by PGF2alpha (139 cows). Conception rate after Ovsynch/TAI was higher than the figure after AI at induced estrus (59.1% vs 20.9%, P<0.05). The dose of GnRH-A was also studied and a practical dose of GnRH-A was found to be 50 microg per cow. To clarify some factors affecting the conception rate after Ovsynch/TAI, 1,558 cows were investigated for the state of their ovaries, days after calving, parity, season, ovarian cyclicity postpartum and nutritional state at the day of Ovsynch. The overall conception rate after Ovsynch/TAI was 51.5%. Fifty-six cows (3.6%) showed estrus at 6 to 7 d after the first injection of GnRH-A. The conception rate after Ovsynch/TAI was low in cows that were 40 to 60 d postpartum, those in their 5th lactation or more, those bred in July to August, and those recovering ovarian cyclicity later than 56 d postpartum. The conception rate after Ovsynch/TAI was high in cows in which body condition score (BCS) was 3.75 at dry period and 3.0 at the day of Ovsynch. In conclusion, Ovsynch/TAI is an effective tool for the reproductive management of dairy cows. A steady and sufficient conception rate after Ovsynch/TAI could be expected by taking the factors affecting the conception rate into the consideration.  相似文献   

4.
The effect of gonadotropin-releasing hormone analogue (GnRH-A) or follicular aspiration at the onset of progesterone-based timed artificial insemination (TAI) on subsequent follicular growth and synchronization of ovulation was examined in early postpartum Japanese Black cows. A total of 40 (22 in Exp. 1 and 18 in Exp. 2) Japanese Black cows at 20-30 days postpartum were fitted with a progesterone releasing internal device (PRID) for 7 days, injected with a prostaglandin F2α analogue upon removal of the PRID and GnRH-A 48 h later, and inseminated 18 h after GnRH-A injection. In Exp. 1, the animals were divided into three groups (untreated control, GnRH-A injection or follicular aspiration) of different treatments on the first day of PRID insertion (day 0), and the synchronized ovulation rate in the follicular aspiration group (100%; 8/8) tended to be higher (P = 0.077) than that in the control group (42.9%; 3/7). In Exp. 2, follicular growth in the GnRH (n = 9) and follicular aspiration (n = 9) groups was monitored by ultrasonography. Four out of the nine animals in the GnRH group had a corpus luteum on either day 4 or day 7 (OV group), and the other five animals had no induced ovulation (NOV group). The diameter of the ovulatory follicle on day 9 in the OV group (1.44 ± 0.11 cm) tended to be greater (P = 0.078) than that in the NOV group (1.13 ± 0.07 cm). Follicular aspiration at the onset of PRID-based TAI of early postpartum Japanese Black cows, regardless of the resumption of ovarian cyclicity, tended to result in a higher rate of synchronization of ovulation than that of the untreated controls.  相似文献   

5.
This report reviews the most recent developments in prostaglandin‐based oestrous synchronization programmes for postpartum dairy cows and addresses the efficiency of controlled breeding protocols based on such developments for cows with abnormal ovarian conditions. A double prostaglandin protocol applied 11–14 days apart seems to be capable of bringing most cows to oestrus. Because of varying oestrus onset times, improved conception rates are obtained following artificial insemination (AI) at detected oestrus rather than fixed‐time AI in prostaglandin‐treated cows. The administration of oestradiol or human chorionic gonadotrophin, or both these hormones, after prostaglandin treatment, improves the synchrony of oestrus yet does not enhance the conception rate. Progesterone‐based treatments for oestrous synchronization are considered the most appropriate for non‐cyclic or anoestrous postpartum dairy cows; prostaglandin alone being ineffective because of the absence of a mature corpus luteum in these cows. Improved oestrus synchrony and fertility rate have been reported using short‐term progesterone treatment regimes (7–9 days) with or without oestradiol benzoate combined with the use of a luteolytic agent given 1 day before, or at the time of, progesterone withdrawal. The ovulation synchronization (Ovsynch) protocol, based on the use of gonadotrophin releasing hormone and prostaglandin, was developed to coordinate follicular recruitment, CL regression and the time of ovulation. This protocol allows fixed time insemination and has proved effective in improving reproductive management in postpartum dairy cows. However, timed AI following Ovsynch seems to have no beneficial effects in heifers, because of an inconsistent follicle wave pattern, and in anoestrous cows, given their lack of prostaglandin responsive CL. To date, there are several prostaglandin based, fixed‐time insemination oestrous synchronization protocols for use in early postpartum dairy cows with ovarian disorders such as ovarian cysts and acyclicity.  相似文献   

6.
Synchronization of oestrus and/or ovulation can reduce workload in heifer reproductive management. The objective of this study was to compare two protocols to synchronize oestrus and/or ovulation using GnRH and prostaglandin F2α (PGF2α) in dairy heifers concerning their effect on follicular dynamics and reproductive performance. Four trials were carried out. In trial 1, 282 heifers were treated with GnRH and PGF2α 7 days apart (GP protocol). One group was inseminated on detection of oestrus (IDO 1), and the other group received two timed artificial inseminations (AI) 48 and 72 h after PGF2α administration (TAI 1). In trial 2, 98 heifers were synchronized with the same GP protocol. Heifers in IDO 2 were treated as in IDO 1, heifers in TAI 2 received two TAI 48 and 78 h after PGF2α administration. In trial 3, heifers in IDO 3 (n = 71) were again treated as in IDO 1. Heifers in TAI 3 (n = 166) received a second dose of GnRH 48 h after PGF2α (GPG protocol) and TAI together with this treatment and 24 h later. Trial 4 compared the timing of ovulation after the GP and the GPG protocol, using a subgroup of the heifers from trials 1 to 3. The ovaries of the heifers were scanned via ultrasound at 48, 56, 72, 80, 96 and 104 h after PGF2α administration. Timing of ovulation and size of the ovulatory follicles were compared between the two groups. In trials 1 to 3, conception rates to first service were between 49 and 66%. They did not differ significantly between IDO and TAI groups within or between trials. Pregnancy rates per synchronization were numerically higher in the TAI groups, but the difference was not significant. Conception rates to breeding on spontaneous oestrus in heifers returning to oestrus were higher than that after synchronized oestrus. In trial 4, more heifers ovulated before the end of the observation period in GPG than in GP (96.5% vs 74.7%; p < 0.001). Overall, ovulatory follicles were smaller in GPG (13.1 ± 1.9 mm vs 14.3 ± 1.9 mm; p < 0.001).  相似文献   

7.
Our objectives were to compare the relative efficacies of three protocols designed to synchronize ovulation for timed artificial insemination (AI) of predominantly Brahman-influenced cows and heifers. In Exp. 1, 273 Brahman x Hereford (F1) cows at three locations were stratified by BW, body condition score (BCS), age, and days postpartum and assigned randomly to three treatments: 1) Syncro-Mate-B (SMB), 2) norgestomet-prostaglandin (NP), and 3) Ovsynch. The management goal required that cows have a minimum BCS of 5 and be at least 36 d postpartum (PP) at treatment onset. However, final results included 23 cows (8.4%) whose BCS fell below 5. In Exp. 2, 286 pubertal beef heifers were stratified by BW and BCS and allocated randomly to the three treatments. Heifers were predominantly Brahman crossbred (n = 265; Brahman x Hereford, F1; Santa Cruz) or purebred Brahman-influenced (Santa Gertrudis) with a smaller number (n = 21) of Hereford heifers also included. For both experiments, SMB treatment consisted of a 9-d norgestomet ear implant plus an estradiol valerate/norgestomet injection on d 0. Norgestomet-prostaglandin-treated females were implanted with a SMB implant without the estradiol valerate/norgestomet injection at the time of implant insertion and received 25 mg prostaglandin F2alpha (PGF) i.m. 2 d before implant removal. Ovsynch consisted of 100 microg GnRH i.m. on d 1, 25 mg PGF i.m. on d 8, and a second GnRH injection on d 10. Beginning on d 9, calves were removed for 48 h in Exp. 1. Cattle in SMB and NP groups in both experiments were timed-inseminated 48 to 54 h after implant removal and at 12 to 24 h after the second GnRH injection (Ovsynch). Timed AI conception rates did not differ between the SMB (45.1%) and Ovsynch (42.4%) groups; however, conception rate in the NP group tended (P < 0.12) to be lower overall than in the other groups due to a reduced (P < 0.05) conception rate in cows that were < 60 d PP at treatment onset. Conversely, timed-AI conception was greatest (P < 0.056) in NP (54.7%) compared with SMB (40.4%) and Ovsynch (39.1%) for heifers in Exp. 2. We conclude that in mature, suckled beef cows with Brahman genetic influence, SMB and Ovsynch perform similarly when cow eligibility relies primarily on BCS and minimum days PP. The NP treatment results in lower conception in cows < 60 d PP compared with SMB and Ovsynch. However, in nulliparous Brahman-influenced heifers that are confirmed to be pubertal, NP may be superior to the other two treatments for timed AI.  相似文献   

8.
Ovsynch is a program developed to synchronize ovulation for timed breeding. In this paper, the authors investigate whether controlled internal drug release (CIDR)-based protocols prevent premature ovulation before timed-artificial insemination (AI) when Ovsynch is started a few days before luteolysis in cycling beef cows. Nine beef cows at 16 days after oestrus were treated with (1) Ovsynch, i.e. gonadotropin releasing hormone (GnRH) analogue on day 0, prostaglandin (PG) F(2alpha) analogue on day 7 and GnRH analogue on day 9 with timed-AI on day 10, (n=3); (2) Ovsynch+CIDR (Ovsynch protocol plus a CIDR for 7 days from day 0, n=3), or (3) oestradiol benzoate (OB)+CIDR+GnRH (OB on day 0 in lieu of the first GnRH treatment, followed by the Ovsynch+CIDR protocol, n=3). In the Ovsynch group (1) plasma progesterone concentrations fell below 0.5 ng/mL earlier (day 5) than in both CIDR-treated groups (2) and (3), where this occurred on day 8. Plasma oestradiol-17beta concentrations peaked on day 8 in the Ovsynch group and on day 9 in both CIDR-treated groups. The dominant follicle ovulated on day 10 in the Ovsynch group and on day 11 in both CIDR-treated groups. Thus, both CIDR-based protocols prevented premature ovulation before timed-AI in Ovsynch when the protocol was started a few days before luteolysis. This reflects the fact that progesterone levels remained high until the beef cattle were treated with PGF(2alpha).  相似文献   

9.
This study evaluated the association between plasma anti-Mullerian hormone (AMH) concentration and fertility in Nelore (Bos indicus) heifers submitted to timed artificial insemination (TAI). At the onset of the synchronization protocol, heifers (n = 289) received a subcutaneous P4 ear implant (3 mg) and 2 mg of oestradiol benzoate. Eight days later, the P4 implant was removed and 0.5 mg of oestradiol cypionate, prostaglandin (0.265 mg, i.m.) and equine chorionic gonadotropin (300 UI, i.m.) was administered, and TAI was performed 48 hr after ear implant removal. Ovarian ultrasound evaluations were performed to measure number of ovarian follicles, dominant follicle size and ovulation response. Pregnancy diagnosis was performed by ultrasound 30 days after AI. Heifers with greater circulating AMH had more antral follicles, a smaller dominant follicle near timed ovulation and lower ovulation response to the timed AI protocol compared to heifers with lower circulating AMH. Although AMH and pregnancy outcome had a quadratic-shaped pattern, AMH was not significantly associated with fertility. In conclusion, heifers with lower AMH had larger follicles towards the end of the synchronization protocol and greater ovulation responses, whereas greater circulating AMH was unrelated to conception success.  相似文献   

10.
Three experiments were conducted to evaluate methods to decrease or eliminate the detection of estrus inherent to a melengestrol acetate (MGA)-PGF2alpha (PGF) protocol for synchronization of estrus in heifers. In each experiment, all heifers received 0.5 mg of MGA x animal(-1) x d(-1) for 14 d (d -32 to -19) and PGF (25 mg, i.m.; d 0, 0 h) 19 d after the last feeding of MGA (MGA-PGF protocol). In Exp. 1, heifers (n = 709) were assigned to each of the following protocols: 1) the MGA-PGF protocol with AI 6 to 12 h after detection of estrus (estrus AI; MGA-PGF); 2) MGA-PGF plus 100 microg, i.m. of GnRH on d -7 (1x GnRH) and estrus AI; or 3) MGA-PGF, GnRH on d -7, and GnRH (100 microg, i.m.) at 48 h after PGF, coincident with insemination (2x GnRH-TB48). In Exp. 2, heifers (n = 559) received the MGA-PGF protocol and were inseminated by either estrus AI or fixed-time AI (TAI) at 60 h, coincident with an injection of GnRH (GnRH-TB60). In Exp. 3, all heifers (n = 460) received the MGA-PGF protocol and were inseminated by estrus AI when detected up to 73 h. Heifers not observed in estrus by 73 h received TAI between 76 and 80 h. Half the heifers inseminated by TAI received no further treatment (TB80), and the remaining half was injected with GnRH at insemination (GnRH-TB80). Variance associated with the interval to estrus and the proportion in estrus from d 0 to 5 was similar for 1x GnRH and MGA-PGF treatments in Exp. 1. Pregnancy rate (d 0 to 5) did not differ for the MGA-PGF and 1x GnRH treatments (62.5 and 60.4%, respectively), and both were greater (P < 0.05) than TAI pregnancy rate in the 2x GnRH-TB48 treatment (42.3%). In Exp. 2, the peak estrous response occurred 60 h after PGF. Pregnancy rate during the synchrony period was greater (P < 0.05) for the MGA-PGF (255/401; 63.6%) than the GnRH-TB60 (74/158; 46.6%) treatment. In Exp. 3, 75.7% of heifers (348/460) were detected in estrus by 73 h and were inseminated, with a conception rate of 74.4%. Pregnancy rates after TAI did not differ between TB80 and GnRH-TB80 (14/56 = 25% and 19/ 56 = 33.9%, respectively). Total pregnancy rate was 63.5% for heifers inseminated after detected estrus and by TAI. Collectively, these data indicate that the exclusive use of TAI for heifers treated with the MGA-PGF protocol resulted in lower pregnancy rates than when AI was performed after detection of estrus. However, estrus AI for 3 d and TAI at the end of d 3 could result in pregnancy rates similar to those achieved after a 5-d period of detecting estrus.  相似文献   

11.
Three experiments were conducted to investigate the ischiorectal fossa (IRF) as a route for the administration of prostaglandin F2 alpha (dinoprost) in cattle. In Experiment 1, 21 nonlactating Holstein cows were given 100 micrograms of gonadotropin releasing hormone (GnRH), intramuscularly (i.m.), and, 7 d later, 25 mg of dinoprost into the IRF. Sixteen cows had serum progesterone concentrations > or = 1.0 ng/mL at the time of dinoprost treatment, and all of these had rapid and complete luteolysis; the other 5 cows were not considered to have a functional corpus luteum (CL) at the time of treatment. There were minimal adverse behavioral reactions to the IRF injections and no visible or palpable tissue reactions at the injection site. In Experiment 2, 74 Holstein heifers were given 25 mg of dinoprost by IRF injection. Luteolysis occurred in 84.3% of the heifers with a functional CL (as determined by the serum progesterone concentration at the time of treatment). Of the heifers bred by either natural service or artificial insemination, 61.8% became pregnant. In Experiment 3, 48 beef heifers received dinoprost 7 d after ovulation, as follows: 25 mg, i.m. (n = 9); 25 mg, IRF (n = 10); 10 mg, IRF (n = 10); 10 mg, subcutaneously (s.c.) (n = 10); or 10 mg, intravulvosubmucosally (IVSM) (n = 9). Fewer heifers (P < 0.05) were found to be in estrus or ovulating in the 10 mg IVSM group (0% and 11%, respectively) than in the 25 mg i.m. group (100% and 100%), the 25 mg IRF group (90% and 100%, respectively), or the 10 mg IRF group (80% and 80%). The rates of estrus (50%) and ovulation (50%) were intermediate in the 10 mg s.c. group. In summary, 25 mg of dinoprost injected into the IRF caused minimal behavioral or tissue response and induced luteolysis and fertile estrus. In addition, 10 mg of dinoprost injected into the IRF was as efficacious as 25 mg given either i.m. or into the IRF in inducing estrus and ovulation.  相似文献   

12.
The working hypotheses in this experiment were: that ovarian estradiol would inhibit luteinizing hormone (LH) secretion in heifers that were anestrus as a result of restricted dietary energy intake and the responsiveness of LH secretion to estradiol negative feedback would decrease during the period when restoration of estrous cycles occurred following feeding of diets adequate in energy. Fifteen heifers weighing 341 +/- 12 (mean +/- SE) kg were fed a diet containing 50% of the energy required for maintenance until 40 to 50 d following cessation of estrous cycles. Heifers were assigned to intact control (C, n = 5), ovariectomized (OVX, n = 5) or ovariectomized-estradiol-17 beta-implanted (OVX + E2, n = 5) treatments. Heifers were subsequently provided a high-energy (HE) diet until termination of the study. Progesterone concentrations indicating cessation of corpus luteum function were detected after heifers had lost 71 +/- 8 kg body weight over 186 +/- 28 d. Control heifers re-initiated estrous cycles as indicated by increased progesterone concentrations in serum at 49 +/- 9 d after initiation of feeding the HE diet (360 +/- 18 kg body weight). Initiation of pulsatile LH secretion was observed in heifers by d 12 following OVX. Estradiol suppressed LH secretion in OVX + E2 heifers during the period of nutritional anestrus in C heifers. Suppressive effects of E2 on LH secretion continued in OVX heifers after C heifers had initiated corpus luteum function. Therefore, the working hypothesis that LH secretion is inhibited by E2 in the nutritionally anestrous heifer is accepted but responsiveness to estradiol does not subside with re-initiation of estrous cycles, thus this working hypothesis is rejected.  相似文献   

13.
This is a review of the physiology and endocrinology of the estrous cycle and how ovarian physiology can be manipulated and controlled for timed artificial insemination (TAI) in beef and dairy cattle. Estrus detection is required for artificial insemination (AI), but it is done poorly in dairy cattle and it is difficult in beef cattle. Protocols that synchronize follicle growth, corpus luteum regression and ovulation, allowing for TAI, result in improved reproductive performance, because all animals are inseminated whether they show estrus or not. As result, TAI programs have become an integral part of reproductive management in many dairy herds and offer beef producers the opportunity to incorporate AI into their herds. Gonadotropin-releasing hormone-based protocols are commonly used in North America for estrus synchronization as part of a TAI program. Protocols that increase pregnancy rates in lactating dairy cows and suckling beef cows have been developed. Protocols that improve pregnancy rates in heifers, acyclic beef cows, and resynchronized lactating dairy cows are also discussed.  相似文献   

14.
Beef cows (n = 473) from two locations were stratified by breed, postpartum interval, age, and AI sire and were randomly allotted to one of four treatments for synchronization of ovulation. Ovulation synchronization protocols included the Ovsynch protocol with (n = 114) or without (n = 123) 48-h calf removal from d 7 to 9 (d 0 = 1st GnRH injection) or the CO-Synch protocol with (n = 119) or without (n = 117) 48-h calf removal from d 7 to 9. The Ovsynch protocol included administration of GnRH (100 microg; i.m.) on d 0, PGF2alpha (25 mg; i.m.) on d 7, GnRH (100 microg; i.m.) on d 9, and timed insemination on d 10. The CO-Synch protocol included administration of GnRH (100 microg; i.m.) on d 0, PGF2alpha (25 mg; i.m.) on d 7, and GnRH (100 microg; i.m.) with timed insemination on d 9. Blood samples were collected from all cows on d -10 and d 0 for analysis of serum progesterone. Cows with at least one serum progesterone concentration greater than 1 ng/mL were considered to be cyclic at the time of treatment. Conception rates of cows that received the CO-Synch + calf removal, Ovsynch + calf removal, CO-Synch, or Ovsynch protocol (63, 61, 54, and 52%, respectively) were not different (P = 0.50). Conception rates were not different (P = 0.80) among CO-Synch- and Ovsynch-treated cows; however, both estrual status and 48-h calf removal affected conception rates. Conception rates of cyclic cows (66%) were greater (P = 0.01) than those of anestrous cows (53%), regardless of which synchronization protocol was used. When data were pooled across synchronization protocol, conception rates of cows with 48-h calf removal (62%) were greater (P = 0.09) than conception rates of cows without calf removal (53%). The CO-Synch + calf removal protocol induces a fertile ovulation in cyclic and anestrous cows, requires handling cattle just three times, results in high conception rates from timed insemination, and should be a useful program for synchronization of ovulation in beef cows.  相似文献   

15.
试验旨在研究同期发情和同期排卵－定时输精技术在青年奶牛中的应用。选择1046头澳大利亚进口荷斯坦青年奶牛,随机分为两组:一组自然发情人工授精配种(对照组);另一组采用前列腺素F2α(PGF2α)诱导母牛发情或按照同期排卵－定时输精程序(Ovsynch或Ovsynch+CIDR法)处理母牛后人工授精配种(试验组),统计同期发情率、不返情率、第一次人工授精妊娠率和21d妊娠率等繁殖指标。结果表明,试验组青年奶牛人工授精后不返情率和第一次人工授精妊娠率与对照组间无显著差异(P>0.05),但21d妊娠率显著高于对照组(53.1%和35.3%,P<0.05)。试验组中,1次PG法、间隔7d2次PG法和间隔11d2次PG法的同期发情率分别为76.1%、81.7%和84.6%,差异均不显著(P>0.05);同期排卵－定时输精组中,Ovsynch法(GPG)和Ovsynch+CIDR法(GPG+CIDR)的不返情率、第一次人工授精妊娠率和21d妊娠率间无显著差异(P>0.05)。不同输精人员可显著影响青年奶牛的第一次人工授精妊娠率(P<0.05),而不同公牛常规冷冻精液对青年奶牛第一次人工授精妊娠率无显著影响(P>0.05)。同期发情及同期排卵－定时输精技术可使青年奶牛集中发情,提高参配率,从而提高21d妊娠率,有效加快青年奶牛人工授精效率,降低饲养成本。  相似文献   

16.
The objective of the experiment was to study follicular dynamics and characteristics of ovulations in dairy heifers after application of the Ovsynch protocol in the last third of estrous cycle. Therefore, altogether 27 regular cycling Holstein heifers were given an injection of GnRH on day 14, 16 or 18 (9 heifers each in group 1 to 3) of the estrous cycle. All heifers were administered PGF2alpha seven days later. Blood was collected for progesterone determination, just before, 24 hours and 48 hours after the PGF2alpha injection. A second injection of GnRH was administered 48 hours after the PGF2alpha injection. Ovarian follicular dynamics were monitored by frequent ultrasound scanning of the ovaries after first and second GnRH injection. Altogether 22 of 27 heifers (81.5%) ovulated 27 to 33 h after first GnRH injection. In 4 heifers ovulations were recorded 45 to 51 h after first GnRH application. Mean intervals between GnRH application and ovulation were 33.0, 33.6 and 28.3 h, respectively. At the time of PGF2alpha injection mean progesterone concentrations were similar in groups 1 and 2, but significantly lower than in group 3. After the second GnRH treatment 5,6 and 8 heifers had ovulations.The average intervals from the second GnRH treatment to ovulation were 24.8, 24.0 and 24.4 h respectively.The results show that Ovsynch is not sufficient to ensure synchronisation of oestrous and ovulation in each animal treated.  相似文献   

17.
Two experiments were conducted to investigate the response of the bovine corpus luteum to surges of luteinizing hormone (LH) induced by natural gonadotropin-releasing hormone (GnRH) administered twice during the same estrous cycle. In experiment 1, eight mature beef cows, each cow serving as her own control, were injected intravenously (iv) with saline on days 2 and 8 of the cycle (day of estrus = day 0 of the cycle), then with 100 micrograms GnRH on days 2 and 8 of the subsequent cycle. Jugular blood samples were taken immediately prior to an injection and at 15, 30, 45, 60, 120 and 240 min postinjection, to quantitate changes in serum luteinizing hormone. Blood was also collected on alternate days after an injection until day 16 of the cycle, to characterize changes in serum progesterone concentrations. Although exogenous GnRH caused release of LH on days 2 and 8 of the cycle, the quantity of LH released was greater on day 8 (P less than .025). Serum levels of progesterone after treatment with GnRH on day 8 of the cycle did not differ significantly from those observed during the control cycles of the heifers. Because exposure of the bovine corpus luteum to excess LH, induced by GnRH early during the estrous cycle, causes attenuated progesterone secretion during the same cycle, these data suggest that a second surge of endogenous LH may ameliorate the suppressive effect of the initial release of LH on luteal function. Duration of the estrous cycle was not altered by treatment (control, 20.4 +/- .5 vs. treated, 20.4 +/- .4 days).(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

18.

Background

The study was designed to test the effect of fixed-time artificial insemination (fixed-AI) after the slightly modified Ovsynch protocol on the pregnancy rate in beef cattle in Finnish field conditions. The modification was aimed to optimize the number of offsprings per AI dose.

Methods

Ninety Charolais cows and heifers were entered into the program an average of 1.8 times. Thus, 164 animal cases were included. Animals were administered 10-12 μg of buserelin. Seven days later animals without a corpus luteum (CL) were rejected (20.7%) while the remaining 130 cases with a CL were administered prostaglandin F2α, followed 48 h later with a second injection of buserelin (8-10 μg). Fixed-AI was performed 16-20 hours after the last injection.

Results

The pregnancy rate was 51.5% (67/130). The pregnancy rate after a short interval (50-70 d) from calving to entering the program was significantly higher than that after a long interval (>70 d).

Conclusion

This protocol seems to give acceptable pregnancy results in beef herds and its effect on saving labour is notable.  相似文献   

19.

The objective of this study was to evaluate the fertility of sexed semen compared with conventional semen with regard to the puberty and breeding ages of Holstein dairy heifers subjected to double Ovsynch protocol with fixed time of artificial insemination. A total of 468 Holstein heifers were divided into two groups. The first group was 122 dairy heifers inseminated via conventional semen, while the second group was 346 heifers inseminated with sexed semen. The puberty and breeding ages of heifers were determined from the farm records. Estrus was synchronized using the double Ovsynch protocol. Numbers were estimated for pregnancy at 40 and 60 days post insemination, embryonic loss, and abortion. The results revealed that the heifers inseminated with sexed semen had a significantly lower first-service pregnancy rate (51.45%) than those inseminated with conventional semen (61.47%). Heifers achieving puberty before 350 days old had a higher pregnancy rate. Embryonic losses and abortion rates did not differ between the two types of semen. Holstein heifers subjected to Ovsynch protocol with sexed semen had an acceptable first-insemination pregnancy rate. Even the applications of sexed semen reduce the reproductive fertility and pregnancy rate in Holstein heifers.

  相似文献   

20.
Two experiments were designed to investigate the administration of intravaginal progesterone in protocols for oestrus and ovulation synchronization in beef heifers. In Experiment 1, cyclic Black Angus heifers (n = 20) received an Ovsynch protocol and were randomly assigned to receive (CIDR‐Ovsynch) or not (Ovsynch) a progesterone device between Days 0 and 7. Treatment with a controlled internal drug release (CIDR) device significantly increased the size of the dominant follicle prior to ovulation (12.8 ± 0.4 CIDR‐Ovsynch vs 11.4 ± 0.4 Ovsynch) (p < 0.02). Plasma progesterone concentrations throughout the experiment were affected by the interaction between group and day effects (p < 0.004). In Experiment 2, cyclic Polled Hereford heifers (n = 382) were randomly assigned to one of the six treatment groups (3 × 2 factorial design) to receive a CIDR, a used bovine intravaginal device (DIB), or a medroxiprogesterone acetate (MAP) sponge and GnRH analogues (lecirelin or buserelin). All heifers received oestradiol benzoate plus one of the devices on Day 0 and PGF on Day 7 pm (device withdrawal). Heifers were detected in oestrus 36 h after PGF and inseminated 8–12 h later, while the remainder received GnRH 48 h after PGF and were inseminated on Day 10 (60 h). The number of heifers detected in oestrus on Day 8 and conception rate to AI on Day 9 were higher (p < 0.01) in the used‐DIB than in the CIDR or MAP groups, while the opposite occurred with the pregnancy rate to FTAI on Day 10 (p < 0.01). There was no effect of progesterone source, GnRH analogue or their interaction on overall pregnancy rates (64.9%). Progesterone treatment of heifers during an Ovsynch protocol resulted in a larger pre‐ovulatory follicle in beef heifers. Progesterone content of intravaginal devices in synchronization protocols is important for the timing of AI, as the use of low‐progesterone devices can shorten the interval to oestrus.  相似文献   

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