RESUMO
Knowledge of follicular wave dynamics obtained through the use of real-time ultrasonography and the development of the means by which follicular wave dynamics can be controlled have provided practical approaches for the in vivo and in vitro production and transfer of embryos in cattle. The elective control of follicular wave emergence and ovulation has had a great impact on the application of on-farm embryo transfer, especially when large groups of donors need to be superstimulated at the same time. Although estradiol and progestins have been used for many years, practitioners in countries where estradiol cannot be used have turned to alternative treatments, such as mechanical follicle ablation or the administration of GnRH for the synchronization of follicle wave emergence. In vitro embryo production also benefits from the synchronization of follicle wave emergence prior to Cumulus Oocyte Complexes (COCs) recovery. As Bos indicus cattle have high antral follicle population, large numbers of oocytes can be obtained by ovum pick-up (OPU) without superstimulation. However, synchronization of follicular wave emergence and superstimulation is necessary to obtain high numbers of COCs by OPU and blastocysts following in vitro fertilization in Bos taurus donors. Finally, embryos can now be transferred in commercial beef or dairy herds using efficacious synchronization and re-synchronization protocols that are easily implemented by farm personnel. These technologies can also be used to resolve reproductive problems such as the reduced fertility observed during summer heat stress and/or in repeat-breeder cows in commercial dairy herds.
RESUMO
O objetivo deste trabalho retrospectivo foi analisar o efeito do local de inovulação e do tamanho docorpo lúteo sobre a taxa de prenhez em novilhas receptoras de embriões produzidos in vitro (PIV). Analisaram-se524 transferências de embriões PIV, sendo 371 oriundas de embriões frescos e 153 de embriões vitrificados emum programa de transferência em tempo fixo (TETF). A taxa de prenhez nas transferências em tempo fixo comembriões bovinos frescos foi maior do que com embriões vitrificados (P < 0,05). O local de inovulação no cornouterino e o tamanho do corpo lúteo não tiveram efeito sobre a taxa de prenhez em receptoras novilhas emprograma de TETF (P > 0,05).(AU)
The present study aimed to analyze the spot of inovulation and the size of the corpus lutheum effects inthe pregnancy rate of heifers receiving in vitro produced embryos. The transfers of 524 crossbred heifers wereevaluated in a fixed time transfer embryo program. The transfers 371 derived from fresh embryos and 153 ofvitrified ones. The pregnancy rate were superior for fresh than vitrified embryo group (P <0,05). The size of thecorpus lutheum (CL) and the local of inovulation did not have significant effects on the pregnancy rate (P >0,5)on neither fresh nor vitrified embryos.(AU)
Assuntos
Animais , Feminino , Bovinos , Bovinos/embriologia , Corpo Lúteo/anatomia & histologia , Prenhez , Transferência Embrionária/veterináriaRESUMO
O objetivo deste trabalho retrospectivo foi analisar o efeito do local de inovulação e do tamanho docorpo lúteo sobre a taxa de prenhez em novilhas receptoras de embriões produzidos in vitro (PIV). Analisaram-se524 transferências de embriões PIV, sendo 371 oriundas de embriões frescos e 153 de embriões vitrificados emum programa de transferência em tempo fixo (TETF). A taxa de prenhez nas transferências em tempo fixo comembriões bovinos frescos foi maior do que com embriões vitrificados (P 0,05).
The present study aimed to analyze the spot of inovulation and the size of the corpus lutheum effects inthe pregnancy rate of heifers receiving in vitro produced embryos. The transfers of 524 crossbred heifers wereevaluated in a fixed time transfer embryo program. The transfers 371 derived from fresh embryos and 153 ofvitrified ones. The pregnancy rate were superior for fresh than vitrified embryo group (P 0,5)on neither fresh nor vitrified embryos.
Assuntos
Feminino , Animais , Bovinos , Bovinos/embriologia , Corpo Lúteo/anatomia & histologia , Prenhez , Transferência Embrionária/veterináriaRESUMO
The success of a commercial embryo transfer program depends on the production of high numbers of viable embryos from donor cows that result in high numbers of calves born when the embryos are transferred to suitable recipien ts. In recent years, a great deal of effort has been devoted to the development of treatment protocols that permit the efficient use of recipients and result in high pregnancy per recipient synchronized, especially in recipients managed on pasture. One of the most successful alternatives to increase the number of recipients utilized in embryo transfer programs is the use of protocols that allow for embryo transfer without the need for estrus detection, usually called fixed-time embryo transfer (FTET). Pregnancies to FTET have been reported to be similar to those after detection of estrus, but the overall proportion of recipients pregnant over those synchronized are higher because these treatments have increased the proportion of recipients that receive embryos. Treatments that increase pr ogesterone concentrations and pregnancies per embryo transfer have also been investigated in recent years. Most of these treatments have resulted in increased pregnancy per embryo transfer in recipients with Bos indicus influence, while benefit were not so obvious in Bos taurus recipients managed under more optimal conditions. While factors such as the reproductive histor y of the recipients and the stage and quality of embryos may affect pregnancy per embryo transfer, other factors such as estrus detection and the time interval from thawing to transfer do not seem to affect the proportion of recipients pregnant with embryos frozen in ethylene glycol and transferred at a fixed-time.
Assuntos
Animais , Estro/fisiologia , Progesterona , Bovinos/classificaçãoRESUMO
The success of a commercial embryo transfer program depends on the production of high numbers of viable embryos from donor cows that result in high numbers of calves born when the embryos are transferred to suitable recipien ts. In recent years, a great deal of effort has been devoted to the development of treatment protocols that permit the efficient use of recipients and result in high pregnancy per recipient synchronized, especially in recipients managed on pasture. One of the most successful alternatives to increase the number of recipients utilized in embryo transfer programs is the use of protocols that allow for embryo transfer without the need for estrus detection, usually called fixed-time embryo transfer (FTET). Pregnancies to FTET have been reported to be similar to those after detection of estrus, but the overall proportion of recipients pregnant over those synchronized are higher because these treatments have increased the proportion of recipients that receive embryos. Treatments that increase pr ogesterone concentrations and pregnancies per embryo transfer have also been investigated in recent years. Most of these treatments have resulted in increased pregnancy per embryo transfer in recipients with Bos indicus influence, while benefit were not so obvious in Bos taurus recipients managed under more optimal conditions. While factors such as the reproductive histor y of the recipients and the stage and quality of embryos may affect pregnancy per embryo transfer, other factors such as estrus detection and the time interval from thawing to transfer do not seem to affect the proportion of recipients pregnant with embryos frozen in ethylene glycol and transferred at a fixed-time.(AU)