RESUMO
The pregnancy rates obtained after the transfer of cryopreserved in vitro-produced (IVP) embryos are usually low and/or inconsistent. The objective of this study was to evaluate the pregnancy rates of Holstein, Gyr and Holstein × Gyr cattle after the transfer of vitrified IVP embryos produced with X-sorted sperm. Seventy-two Gyr and 703 Holstein females were subjected to ovum pickup (OPU) sessions, followed by in vitro embryo production using semen from sires of the same breeds. Embryos (1636 Holstein, 241 Gyr and 1515 Holstein × Gyr) were exposed to forskolin for 48 h prior to vitrification. The pregnancy rate achieved with Gyr dam and sire was 46.1%, which was similar (p = 0.11) to that of Holstein dam and Gyr sire (40.3%). Crossing Gyr dams with Holstein sires resulted in a pregnancy rate of 38.9% and did not differ (p = 0.58) from the pregnancy rate obtained with the cross between Holstein dams and Gyr sires. The rate obtained with Holstein dam and sire was 32.5%. The average pregnancy rate was 36.6%, and no difference was found in the proportion of female foetuses (88.8%, in average) among breeds (p > 0.05). In conclusion, transfer of cryopreserved X-sorted embryos represents an interesting choice for dairy cattle. Despite the small differences between pregnancy rates, we highlight the efficiency of this strategy for all of the racial groups studied.
Assuntos
Bovinos/embriologia , Criopreservação/veterinária , Transferência Embrionária/veterinária , Fertilização in vitro/veterinária , Taxa de Gravidez , Animais , Cruzamento , Bovinos/genética , Bovinos/fisiologia , Transferência Embrionária/métodos , Feminino , Temperatura Alta , Masculino , Gravidez , Pré-Seleção do Sexo/veterinária , Especificidade da Espécie , EspermatozoidesRESUMO
In vitro embryo production (IVEP) has become an accessible option for meat and milk producers, and Brazil is now the leader of IVEP worldwide. Recipient females represent one of the most significant costs in embryo transfer (ET) programs. Thus, hormonal protocols may increase the proportion of suitable recipients to receive embryos and improve the efficiency of IVEP program s. Besides improving the amount of available recipients, it is important to select high quality animals. Due to the great demand, the type of females that were considered ideal for ET has become scarce, especially for large-scale programs. Therefore, new approaches have successfully emerged, as the use of Nelore cows recently calved as embryo recipients. For being the most numerous category in Brazil, these animals can be acquired for fair prices. Embryo production from slaughterhouse ovaries also represents an innovative strategy for large-scale IVEP. With the use of sorted sperm and large amount of pregnancies, is has become an interesting alternative compared to AI. In this article, recent advances in embryo IVP are discussed, as well as some of the most used hormonal protocols for estrus synchronization of recipients in large-scale IVEP programs.
Assuntos
Animais , Bovinos , Embrião de Mamíferos/embriologia , Fertilização in vitro/métodos , Análise do Sêmen/métodos , Bovinos/classificaçãoRESUMO
In vitro embryo production (IVEP) has become an accessible option for meat and milk producers, and Brazil is now the leader of IVEP worldwide. Recipient females represent one of the most significant costs in embryo transfer (ET) programs. Thus, hormonal protocols may increase the proportion of suitable recipients to receive embryos and improve the efficiency of IVEP program s. Besides improving the amount of available recipients, it is important to select high quality animals. Due to the great demand, the type of females that were considered ideal for ET has become scarce, especially for large-scale programs. Therefore, new approaches have successfully emerged, as the use of Nelore cows recently calved as embryo recipients. For being the most numerous category in Brazil, these animals can be acquired for fair prices. Embryo production from slaughterhouse ovaries also represents an innovative strategy for large-scale IVEP. With the use of sorted sperm and large amount of pregnancies, is has become an interesting alternative compared to AI. In this article, recent advances in embryo IVP are discussed, as well as some of the most used hormonal protocols for estrus synchronization of recipients in large-scale IVEP programs.(AU)