Effect of the presence and location of corpus luteum on competence of bovine cumulus-oocyte complexes

This study aimed to determine the effect of presence of the corpus luteum (CL) and its influence on cumulus­oocyte complexes (COCs) obtained from the ipsilateral or contralateral ovary in bovine on the recovery and capacity of the oocytes to sustain mono-spermic fertilization, undergo preimplantation development, and develop to the blastocyst stage. Ovaries were collected at a local slaughterhouse and kept in pairs corresponding to the same animal. In the first experiment the variables evaluated were compared between cows with (CCL+) and without (CCL- ) CL, and for the second experiment, comparisons were made between ovaries with an ipsilateral (CL+), contralateral (CL−), and no (NCL). The recovery rate of COCs was higher in ovaries from CCL− cows, and a higher proportion of grade 1 COCs were recovered from this group. A higher proportion of metaphase I oocytes at 7 h of maturation, and a higher rate of cleavage were observed in the CCL+ group; however, a higher proportion of embryos were obtained from the CCL− group. Besides, COCs from the CL+ group had a lower proportion of grades 1 and 2 morphological qualities, lower rate of metaphase II oocytes at 22 h of maturation, and lower rate of formation of two pronuclei, whereas a higher proportion of unfertilized oocytes after in vitro fertilization. On the other hand, the COCs from the CL− group displayed a lower proportion of oocytes with more than two pronuclei, higher cleavage rate, and higher final blastocyst production were obtained when compared to CL+. Thus, the effects of CL on the competence of bovine COCs are different depending on the anatomical proximity of their location in the animal, negatively affecting the quality of COCs located in the same ovary, but not having negative effects on the competence of COCs in the ovaries contralateral to their location.(AU)

Desafios técnicos e biológicos na produção in vitro de embriões de búfalo / Desafíos técnicos y biológicos en la producción in vitro de embriones de búfalo

O elevado número de búfalos, junto com seus atributos produtivos, tem convertido a Amazônia brasileira em uma das regiões mais importantes na produção de animais desta espécie fora da Ásia. O uso de biotecnologias reprodutivas tem permitido importantes avanços no melhoramento genético, no entanto, a resposta dos búfalos às diferentes técnicas de reprodução assistida é variável. Atualmente, a produção in vitro de embriões nesta espécie, embora represente uma técnica com resultados promissores, ainda se depara com desafios relacionados com as particularidades estruturais e metabólicas dos gametas e embriões, assim como com as características morfofisiológicas próprias da reprodução dos búfalos. Conjuntamente, essas características compõem os fatores biológicos e técnicos que majoritariamente reduzem a eficiência dos resultados e que obrigam a adaptação dos sistemas e das metodologias utilizadas ao longo do processo de produção de embriões no laboratório. Nesse sentido, representam os pontos chaves que merecem ser analisados em profundidade na procura de melhorar os resultados e alcançar a maior eficiência da técnica quando aplicada à espécie bubalina.

El elevado número de búfalos, junto con sus atributos productivos, han convertido a la Amazonia brasilera en una de las regiones más importantes para la producción de animales de esta especie fuera del continente asiático. La implementación de biotecnologías reproductivas ha permitido importantes avances en el mejoramiento genético, sin embargo, la respuesta de los búfalos a las diferentes técnicas de reproducción asistida es variable. En la actualidad, la producción in vitro de embriones en esta especie, aun cuando representa una técnica con resultados promisorios, enfrenta desafíos relacionados con las particularidades estructurales y metabólicas de los gametos y embriones, así como, con las características morfofisiológicas propias de la reproducción de los búfalos. Conjuntamente, esas características componen los factores de orden técnico y biológico que en mayor medida reducen la eficiencia de los resultados, y que obligan a la adaptación de los sistemas y las metodologías utilizadas a lo largo de la producción de embriones en el laboratorio, por lo tanto, representan los puntos clave que merecen ser analizados a profundidad, en la búsqueda de mejorar los resultados, y de alcanzar la plena eficiencia de la técnica, cuando se implementa en la especie bufalina.

In vitro embryo production in buffaloes: from the laboratory to the farm

Transvaginal follicular aspiration technique together with in vitro embryo production are the biotechnological alternatives currently available to support genetic improvement breeding programs in buffalo species. However, aspects related to animal management, lack of knowledge of the metabolic needs and biochemical peculiarities of gametes and embryos, as well as the reproductive physiology characteristics have hampered progress in the results. Despite the low availability of good quality oocytes collected after OPU in donors as a physiological characteristic of buffalo species, high rates of oocyte maturation, modest embryo cleavage, blastocyst production and pregnancy rates after transvaginal embryo transfer in recipients could be obtained in buffalo in vitro embryo production programs. The results of implementing an in vitro embryo production program in buffaloes in the northern region of Pará state, Brazil, and results published by other groups demonstrate the feasibility of implementing this biotechnology in the routine of breeding programs. Nevertheless, in order to achieve better and consistent results, it is necessary to deepen the knowledge on the peculiarities of reproductive biology in this specie. Selection of donor animals based on ovarian size and ovarian follicular reserve and on the rate of blastocyst production is presented as an effective alternative to increase the efficiency of the in vitro embryo production technique applied to the buffalo species.

In vitro embryo production in buffaloes: from the laboratory to the farm

Transvaginal follicular aspiration technique together with in vitro embryo production are the biotechnological alternatives currently available to support genetic improvement breeding programs in buffalo species. However, aspects related to animal management, lack of knowledge of the metabolic needs and biochemical peculiarities of gametes and embryos, as well as the reproductive physiology characteristics have hampered progress in the results. Despite the low availability of good quality oocytes collected after OPU in donors as a physiological characteristic of buffalo species, high rates of oocyte maturation, modest embryo cleavage, blastocyst production and pregnancy rates after transvaginal embryo transfer in recipients could be obtained in buffalo in vitro embryo production programs. The results of implementing an in vitro embryo production program in buffaloes in the northern region of Pará state, Brazil, and results published by other groups demonstrate the feasibility of implementing this biotechnology in the routine of breeding programs. Nevertheless, in order to achieve better and consistent results, it is necessary to deepen the knowledge on the peculiarities of reproductive biology in this specie. Selection of donor animals based on ovarian size and ovarian follicular reserve and on the rate of blastocyst production is presented as an effective alternative to increase the efficiency of the in vitro embryo production technique applied to the buffalo species.(AU)