Relationships between follicle and corpus luteum size and vascularization with ovulation, progesterone production, and pregnancy in Nellore beef cattle

ABSTRACT The objective of this study was to evaluate the relationships between preovulatory follicle (POF) and corpus luteum (CL) diameters, and POF and CL vascular perfusion with progesterone production, ovulation, and pregnancy in Nellore cows subjected to timed artificial insemination (TAI). Nellore cows (n = 201) were subjected to ovulation synchronization and later to ultrasound evaluation of POF and CL at the time of insemination (D0) and seven days later (D7), respectively. Females were divided into three categories according to the POF diameter assessed at the time of insemination: small (SF), medium (MF), and large (LF) follicles. The LF group had a greater number and intensity of pixels in the POF ultrasound exam compared with the SF group. The CL flow intensity and progesterone concentration were also higher in the LF group. The SF group showed lower flow intensity and lower ovulation rate compared with the others. When non-pregnant females were compared to pregnant ones, no difference was observed in any of the analyzed variables. The results show for the first time in Nellore cattle the relationship between the size of ovarian structures and blood flow (quantity and intensity) as well as the ability of the CL to produce progesterone. The intensity of the POF pixels proved to be relevant, demonstrating correlations with the size and flow of the CL, which were not found when evaluating only the number of pixels, thus revealing the importance of evaluating complementary characteristics of the flow.

Como melhorar os índices reprodutivos em um programa de transferência de embrião equino / How to improve reproductive indices in an equine embryo transfer program

O Brasil é o país que mais faz uso da biotécnica de transferência de embrião (TE) sendo utilizado por quase todas as raças aqui existentes. A raça Mangalarga Marchador lidera a utilização dessa biotécnica incrementando cada vez mais a indústria do cavalo, havendo atualmente leilões apenas de embrião. A TE possibilitou aumentar o número de descendentes de doadoras zootecnicamente superiores sem ser necessário interromper a carreira esportiva dessas éguas. Apesar dos índices de recuperação embrionária e gestação atualmente serem bastante consistentes, a maior dificuldade em operar um programa TE bem-sucedido é a administração e coordenação das muitas variáveis que pode afetar essas taxas. Essas variáveis incluem a gestão das doadoras e receptoras, a qualidade da receptora, a sincronização da ovulação, a competência técnica do operador e os métodos utilizados para realizar a transferência de embriões. Além, disso, interferem ainda a qualidade do embrião, condições uterinas e nutricionais das doadoras e receptoras. O presente artigo visa demonstrar alguns fatores que podem interferir negativamente na TE, e o que podemos fazer para melhorar os índices reprodutivos nos programas de transferência de embrião.(AU)

Nowadays the Brazil is the country that makes the most use of embryo transfer biotechnology (ET) being used by almost all the breeds. The Mangalarga Marchador breed leads this biotechnology increasing the horse industry more and more, because nowadays, there is only an embryo public sale. ET technology has made it possible to increase the numbers of descendants from genetically superior donors without the need to disrupt the mares' sports careers. Although rates of embryo recovery and gestation are currently quite consistent, the greatest difficulty in operating a successful ET program is the management and coordination of the many variables that may affect these rates. These variables include donor and recipient management, recipient quality, synchronization of ovulation, technical skills of the operator and methods used to perform embryo transfer, embryo quality, uterine and nutritional conditions of donors and recipients. This article aims to demonstrate some factors that may negatively interfere in ET, and what we can do to improve reproductive indices in embryo transfer programs.(AU)

Como melhorar os índices reprodutivos em um programa de transferência de embrião equino / How to improve reproductive indices in an equine embryo transfer program

O Brasil é o país que mais faz uso da biotécnica de transferência de embrião (TE) sendo utilizado por quase todas as raças aqui existentes. A raça Mangalarga Marchador lidera a utilização dessa biotécnica incrementando cada vez mais a indústria do cavalo, havendo atualmente leilões apenas de embrião. A TE possibilitou aumentar o número de descendentes de doadoras zootecnicamente superiores sem ser necessário interromper a carreira esportiva dessas éguas. Apesar dos índices de recuperação embrionária e gestação atualmente serem bastante consistentes, a maior dificuldade em operar um programa TE bem-sucedido é a administração e coordenação das muitas variáveis que pode afetar essas taxas. Essas variáveis incluem a gestão das doadoras e receptoras, a qualidade da receptora, a sincronização da ovulação, a competência técnica do operador e os métodos utilizados para realizar a transferência de embriões. Além, disso, interferem ainda a qualidade do embrião, condições uterinas e nutricionais das doadoras e receptoras. O presente artigo visa demonstrar alguns fatores que podem interferir negativamente na TE, e o que podemos fazer para melhorar os índices reprodutivos nos programas de transferência de embrião.

Nowadays the Brazil is the country that makes the most use of embryo transfer biotechnology (ET) being used by almost all the breeds. The Mangalarga Marchador breed leads this biotechnology increasing the horse industry more and more, because nowadays, there is only an embryo public sale. ET technology has made it possible to increase the numbers of descendants from genetically superior donors without the need to disrupt the mares' sports careers. Although rates of embryo recovery and gestation are currently quite consistent, the greatest difficulty in operating a successful ET program is the management and coordination of the many variables that may affect these rates. These variables include donor and recipient management, recipient quality, synchronization of ovulation, technical skills of the operator and methods used to perform embryo transfer, embryo quality, uterine and nutritional conditions of donors and recipients. This article aims to demonstrate some factors that may negatively interfere in ET, and what we can do to improve reproductive indices in embryo transfer programs.

Estresse térmico na reprodução equina / Thermal stress in equine reproduction

Estudos sobre estresse térmico em equinos, geralmente envolvem condições induzidas pelo exercício físico intenso, assim como as alterações fisiológicas que comtemplam o efeito do ambiente em geral são relacionadas ao fotoperíodo e não ao efeito da temperatura como acontece com maior frequência em outras espécies. Verifica-se uma necessidade de maior compreensão dos efeitos deletérios do estresse térmico no desempenho reprodutivo desta espécie, visto que a produção de potros saudáveis é o objetivo de um programa reprodutivo e em geral a principal fonte de retorno econômico da atividade. Esse fato ganha ainda mais relevância diante das condições climáticas e de criação presentes nos trópicos, além da atividade reprodutiva da espécie equina depender de períodos de alta luminosidade ambiental, que coincidem com as maiores temperaturas. O presente trabalho tem por objetivo demonstrar como o estresse térmico ambiental pode promover a redução da fertilidade em fêmeas equinas e alertar para a necessidade de estudos completos envolvendo o tema.(AU)

Studies on thermal stress in equines usually involve conditions induced by intense physical exercise, as well as the physiological changes that contemplate the effect of the environment in general are related to the photoperiod and not to the effect of temperature as it in other species. We need a better understanding of the deleterious effects of thermal stress on the reproductive performance of this species, since the production of healthy foals is generally the objective of a reproductive program and the main source of economic return of the activity. This fact is even more relevant given the climatic and breeding conditions in the tropics, and the reproductive activity of the equine species take place on periods of high luminosity, which coincide with higher temperatures. The present review aims to demonstrate how the environmental thermal stress can promote the reduction of the fertility in equine females and to alert to the necessity of complete studies involving the theme.(AU)

Estresse térmico na reprodução equina / Thermal stress in equine reproduction

Estudos sobre estresse térmico em equinos, geralmente envolvem condições induzidas pelo exercício físico intenso, assim como as alterações fisiológicas que comtemplam o efeito do ambiente em geral são relacionadas ao fotoperíodo e não ao efeito da temperatura como acontece com maior frequência em outras espécies. Verifica-se uma necessidade de maior compreensão dos efeitos deletérios do estresse térmico no desempenho reprodutivo desta espécie, visto que a produção de potros saudáveis é o objetivo de um programa reprodutivo e em geral a principal fonte de retorno econômico da atividade. Esse fato ganha ainda mais relevância diante das condições climáticas e de criação presentes nos trópicos, além da atividade reprodutiva da espécie equina depender de períodos de alta luminosidade ambiental, que coincidem com as maiores temperaturas. O presente trabalho tem por objetivo demonstrar como o estresse térmico ambiental pode promover a redução da fertilidade em fêmeas equinas e alertar para a necessidade de estudos completos envolvendo o tema.

Studies on thermal stress in equines usually involve conditions induced by intense physical exercise, as well as the physiological changes that contemplate the effect of the environment in general are related to the photoperiod and not to the effect of temperature as it in other species. We need a better understanding of the deleterious effects of thermal stress on the reproductive performance of this species, since the production of healthy foals is generally the objective of a reproductive program and the main source of economic return of the activity. This fact is even more relevant given the climatic and breeding conditions in the tropics, and the reproductive activity of the equine species take place on periods of high luminosity, which coincide with higher temperatures. The present review aims to demonstrate how the environmental thermal stress can promote the reduction of the fertility in equine females and to alert to the necessity of complete studies involving the theme.

Morphological characteristics of mule conceptuses during early developmentîen

Hybrids between species are often infertile and extremely rare among mammals. Mules, i.e. crossing between the horse and the donkey, on the other hand are very common in agricultural and leisure practices due to their enhanced post-natal physical characteristics that is believed to occur for outbreeding or hybrid vigor. Since no reports are availableon the effects of hybrid vigor during early development, this study focused on characterizing the intrauterine development of mule conceptuses during critical embryo-to-fetus transition period. Nine embryos and fetuses of early gestation, obtained after artificial insemination and transcervical flushing, were evaluated by means of gross anatomy and histology and compared to data available for the equine. We found that some events, such as C-shape turning, apearence of branchial archs, limb and tail buds, formation of primary and secondary brain vesicles, heart compartmentalization, and development of somites, occurred slightly earlier in the mule. Nonetheless, no major differences were observed in other developmental features, suggesting similarities between the mule and the horse development. In conclusion, these data suggest that the effect of hybrid vigor is present during intrauterine development in the mule, at least with regard to its maternal parent.(AU)

Morphological characteristics of mule conceptuses during early developmentîen

Hybrids between species are often infertile and extremely rare among mammals. Mules, i.e. crossing between the horse and the donkey, on the other hand are very common in agricultural and leisure practices due to their enhanced post-natal physical characteristics that is believed to occur for outbreeding or hybrid vigor. Since no reports are availableon the effects of hybrid vigor during early development, this study focused on characterizing the intrauterine development of mule conceptuses during critical embryo-to-fetus transition period. Nine embryos and fetuses of early gestation, obtained after artificial insemination and transcervical flushing, were evaluated by means of gross anatomy and histology and compared to data available for the equine. We found that some events, such as C-shape turning, apearence of branchial archs, limb and tail buds, formation of primary and secondary brain vesicles, heart compartmentalization, and development of somites, occurred slightly earlier in the mule. Nonetheless, no major differences were observed in other developmental features, suggesting similarities between the mule and the horse development. In conclusion, these data suggest that the effect of hybrid vigor is present during intrauterine development in the mule, at least with regard to its maternal parent.