RESUMO
Over the past two decades, research efforts have resulted in superstimulation protocols that are user-friendly, but embryo production has increased only marginally. Studies to-date have not adequately answered the question of whether superstimulatory protocols can be used to overcome the follicle wave pattern, increase the number of follicles that enter the wave, or rescue a greater number of small follicles within the wave. Studies which appear to facilitate greater utilization of follicles within the wave are described in this review. The number of large follicles at the time of first AI tended to be greater, and more ovulations and CL occurred with lengthened protocol (7-day) than with the convention 4-day FSH treatment. In addition, there was greater synchrony of ovulations and the mean numbers of total ova/embryos, fertilized ova, transferable or freezable embryos were numerically higher in the 7-day group. When used in an in vitro fertilization model, FSH treatment for 7 days resulted in a greater number of follicles for aspiration, a greater proportion of expanded cumulus-oocyte-complexes, and more transferable embryos after in vitro culture. Daily ultrasonography revealed a reduction in the number of small (1-2 mm) antral follicles from the beginning to the end of the superstimulatory treatment that was associated with a progressive shift of follicles to the next size category in both 4-day and 7-day groups. The number of follicles1 mm at the end of superstimulation did not differ from the number of follicles >1 mm at the beginning of Super stimulation. However, the total number of follicles >3 mm at the end of superstimulation, was greater than the number of follicles >3 mm at the beginning of superstimulation due to growth of the 1-2 mm population into larger size categories during treatment.
Assuntos
Feminino , Animais , Bovinos , Bovinos/embriologia , Bovinos/fisiologia , Hormônio Foliculoestimulante/análise , Hormônio Foliculoestimulante/síntese químicaRESUMO
Over the past two decades, research efforts have resulted in superstimulation protocols that are user-friendly, but embryo production has increased only marginally. Studies to-date have not adequately answered the question of whether superstimulatory protocols can be used to overcome the follicle wave pattern, increase the number of follicles that enter the wave, or rescue a greater number of small follicles within the wave. Studies which appear to facilitate greater utilization of follicles within the wave are described in this review. The number of large follicles at the time of first AI tended to be greater, and more ovulations and CL occurred with lengthened protocol (7-day) than with the convention 4-day FSH treatment. In addition, there was greater synchrony of ovulations and the mean numbers of total ova/embryos, fertilized ova, transferable or freezable embryos were numerically higher in the 7-day group. When used in an in vitro fertilization model, FSH treatment for 7 days resulted in a greater number of follicles for aspiration, a greater proportion of expanded cumulus-oocyte-complexes, and more transferable embryos after in vitro culture. Daily ultrasonography revealed a reduction in the number of small (1-2 mm) antral follicles from the beginning to the end of the superstimulatory treatment that was associated with a progressive shift of follicles to the next size category in both 4-day and 7-day groups. The number of follicles<5 mm decreased during superstimulation suggesting that there was no continuous recruitment of small follicles, and the number of follicles>1 mm at the end of superstimulation did not differ from the number of follicles >1 mm at the beginning of Super stimulation. However, the total number of follicles >3 mm at the end of superstimulation, was greater than the number of follicles >3 mm at the beginning of superstimulation due to growth of the 1-2 mm population into larger size categories during treatment. (AU)
Assuntos
Animais , Feminino , Bovinos , Bovinos/embriologia , Bovinos/fisiologia , Hormônio Foliculoestimulante/análise , Hormônio Foliculoestimulante/síntese químicaRESUMO
On a worldwide basis, more than 750,000 embryos are produced annually from superovulated donors and more than 450,000 embryos are produced using in vitro techniques. Superovulation and embryo collection are done as frequentlu as every 30 days. Cryopreservation and direct transfer of frozen-thawed embryos results in pregnancy rates near that of fresh embryos. Since the zona pellucida-infact in vivo produced bovine embryo can be made specified pathogen-free by washing procedures, thousands of frozen embryos are marketed internationally on an annual basis. In vitro embryo production is used widely in countries like Brazil and Japan. Polymerase chain reaction (PCR) technology is currentlu being used for sexing embryos and this technology is beginning to be used for "embryo diagnostics" and "embryoi genomics". Sex-sorted bovine semen is also readily available and is being used increasingly, especially for in vitro embryo production.
Assuntos
Animais , Criopreservação , Embrião de Mamíferos/citologia , Sexo , Bovinos/classificaçãoRESUMO
Although superstimulatory protocols in cattle are usually initiated during mid-cycle, the elective control follicular wave emergence and ovulation have had a great impact on the application of on-farm embryo transfer. However, the most commonly used approach for the sinchronization of follicular wave emergence invoolves the use of estradiol which cannot be used in many parts of the world. Therefore, the need for alternative treatments has driven recent research. An approach that has shown promise is to initiate FSH treatments at the time of the emergence of the first follicular wave folliwing GnRH-induced ovulation. Alternatively, it has been shown that that it may be possible to ignore follicular wave status, and by extending the treatment protocol induce smaller follicles to grow and reach maturity and superovulate. Finally , the short half-life of pintuitary FSH necessitates twice daily treatments which are times consuming, stressful and subject to error. Recent treatment protocols have permitted supertimulation with a single or alternatively two-FSH treatments, reducing the need for animal handling during FSH treatments.
Assuntos
Animais , Embrião de Mamíferos/embriologia , Estradiol/farmacologia , Ovulação/metabolismo , Bovinos/classificação , Fase Folicular/metabolismoRESUMO
Bovine Embryo transfer has been used widely to reproduce the most valuable females in the herd with about 750,000 embryos produced annually from superovulated donors and more than 450,000 embryos produced are the safest and most cost affective alternatives to move genetics internationally because og their low risk of transmitting diseases. One of most important factors associated with the success and widepread application of this technologie is evaluation of the embryos before freezing and/or transfer to a recipient. Embryos are usually classified based on a number code system for their stage of development (1 to 9) and for their quality (1 to 4). The basic principles of embryo evaluation are briefly described.
Assuntos
Superovulação , Bovinos/classificação , Ovulação/fisiologiaRESUMO
Bovine Embryo transfer has been used widely to reproduce the most valuable females in the herd with about 750,000 embryos produced annually from superovulated donors and more than 450,000 embryos produced are the safest and most cost affective alternatives to move genetics internationally because og their low risk of transmitting diseases. One of most important factors associated with the success and widepread application of this technologie is evaluation of the embryos before freezing and/or transfer to a recipient. Embryos are usually classified based on a number code system for their stage of development (1 to 9) and for their quality (1 to 4). The basic principles of embryo evaluation are briefly described.(AU)
Assuntos
Superovulação , Bovinos/classificação , Ovulação/fisiologiaRESUMO
Although superstimulatory protocols in cattle are usually initiated during mid-cycle, the elective control follicular wave emergence and ovulation have had a great impact on the application of on-farm embryo transfer. However, the most commonly used approach for the sinchronization of follicular wave emergence invoolves the use of estradiol which cannot be used in many parts of the world. Therefore, the need for alternative treatments has driven recent research. An approach that has shown promise is to initiate FSH treatments at the time of the emergence of the first follicular wave folliwing GnRH-induced ovulation. Alternatively, it has been shown that that it may be possible to ignore follicular wave status, and by extending the treatment protocol induce smaller follicles to grow and reach maturity and superovulate. Finally , the short half-life of pintuitary FSH necessitates twice daily treatments which are times consuming, stressful and subject to error. Recent treatment protocols have permitted supertimulation with a single or alternatively two-FSH treatments, reducing the need for animal handling during FSH treatments.(AU)
Assuntos
Animais , Embrião de Mamíferos/embriologia , Estradiol/farmacologia , Ovulação/metabolismo , Bovinos/classificação , Fase Folicular/metabolismoRESUMO
On a worldwide basis, more than 750,000 embryos are produced annually from superovulated donors and more than 450,000 embryos are produced using in vitro techniques. Superovulation and embryo collection are done as frequentlu as every 30 days. Cryopreservation and direct transfer of frozen-thawed embryos results in pregnancy rates near that of fresh embryos. Since the zona pellucida-infact in vivo produced bovine embryo can be made specified pathogen-free by washing procedures, thousands of frozen embryos are marketed internationally on an annual basis. In vitro embryo production is used widely in countries like Brazil and Japan. Polymerase chain reaction (PCR) technology is currentlu being used for sexing embryos and this technology is beginning to be used for "embryo diagnostics" and "embryoi genomics". Sex-sorted bovine semen is also readily available and is being used increasingly, especially for in vitro embryo production.(AU)
Assuntos
Animais , Embrião de Mamíferos/citologia , Criopreservação , Sexo , Bovinos/classificaçãoRESUMO
The objective was to determine the effects of exogenous prostaglandin F(2α) (PGF), with or without progesterone treatment, on first ovulation in prepubertal heifers. We tested the hypothesis that PGF has a luteolysis-independent ovulatory effect in cattle. Crossbred Angus heifers (12 to 14 mo old, 250 kg body weight, and an average body condition score of 3 out of 5) were examined by transrectal ultrasonography on two occasions, 11 days apart. Heifers in which a CL was not detected at either examination were considered prepubertal. Heifers were assigned randomly to three experimental groups: (1) PG group (N = 14); heifers were treated with a PGF analog (500 µg cloprostenol im) 5 days after the emergence of a spontaneous (i.e., naturally occurring, noninduced) follicular wave; (2) PPG group (N = 12); heifers were given an intravaginal progesterone-releasing insert (CIDR; Pfizer Animal Health, Montreal, QC, Canada), and a follicular wave was induced with 50 mg of progesterone + 2 mg of estradiol benzoate im, and a PGF analog was given at the time of CIDR removal, on day 5 of the follicular wave (on average, 8.6 ± 0.5 days after CIDR insertion); and (3) control group heifers were given no treatment (N = 14). Heifers were examined daily by transrectal ultrasonography from the start of the experiment to confirmation that ovulation had occurred, or to 5 days after PGF injection (PG and PPG groups) or until dominant follicles of the next follicular wave reached 8 mm (control group). The percentage of heifers that ovulated within 10 days after wave emergence was higher in PPG (10/12; 83.3%) and PG (11/14; 78.5%) groups than in control (1/14; 7.1%; P < 0.0001). Ovulations occurred 69.6 ± 6 h and 93.8 ± 5 h after PGF treatment in PPG and in PG groups, respectively, whereas only one heifer in the control group ovulated 96 h after day 5 of follicular wave (P = 0.13). In summary, PGF treatment was associated with ovulation in prepubertal heifers whether or not exogenous progesterone was used as a pretreatment. The hypothesis that PGF will induce ovulation by a luteolysis-independent mechanism was supported.
Assuntos
Bovinos , Dinoprosta/administração & dosagem , Indução da Ovulação/veterinária , Maturidade Sexual , Administração Intravaginal , Animais , Cloprostenol/administração & dosagem , Corpo Lúteo/diagnóstico por imagem , Feminino , Folículo Ovariano/diagnóstico por imagem , Folículo Ovariano/efeitos dos fármacos , Folículo Ovariano/fisiologia , Indução da Ovulação/métodos , Progesterona/administração & dosagem , UltrassonografiaRESUMO
Two experiments evaluated the effects of timing of the induction of ovulation in superstimulated lactating Holstein donor cows that were fixed-time artificially inseminated. Secondary objectives were to evaluate the effects of the timing of progesterone (P4) device removal (Experiment 1) or the addition of a second norgestomet implant (Experiment 2) during superstimulation. In Experiment 1, 12 cows were allocated to one of four treatment groups with the timing of P4 device removal (24 or 36 h) and pLH treatment (48 or 60 h), after the first PGF as main factors, in a Latin Square (cross-over) design. There was an interaction (P = 0.03) between time of P4 device removal and time of pLH treatment. Mean (± SEM) numbers of transferable embryos were higher when the P4 device was removed at 36 h and pLH was administered at 60 h after the first PGF (P36LH60 =6.3 ± 1.4) compared to other treatments (P24LH60 =3.7 ± 1.1; P24LH48 =2.4 ± 0.8; or P36LH48 =2.2 ± 0.7). In Experiment 2, 40 cows were randomly allocated into one of four treatments with the number of norgestomet implants (one or two) and the time of induction of ovulation with GnRH relative to the first PGF (48 vs. 60 h) as main effects. The mean number of transferable embryos was higher (P = 0.02) when GnRH was administered at 60 h (4.2 ± 1.3) compared to at 48 h (2.7 ± 0.8), and the number of freezable embryos was increased (P = 0.01) in cows receiving two (3.0 ± 1.0) rather than one norgestomet implant (1.5 ± 0.5). In summary, embryo production in lactating Holstein cows was increased when the ovulatory stimulus (pLH or GnRH) was given 60 h after the first PGF, particularly when the P4 device was removed 36 h after the first PGF and when two norgestomet ear implants were used during the superstimulation protocol.