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Objective: To assess the testicular and semen characteristics of Tropical Milking Criollo (CLT) bulls in the subhumid Mexican tropics. Design/methodology/approach: Eight bulls were evaluated and distributed in two groups: G1 (n5): young bulls and G2 (n3): adult bulls. All bulls were managed under grazing and evaluated throughout a year. From each bull, the following measurements were taken once a month: live weight, body condition score, scrotal circumference, and testicular width, length and volume. Semen was obtained every 3 months via an artificial vagina. The evaluated semen variables were: aspect, volume, mass and individual motility, and sperm concentration and morphology. Results: Live weight and testicular measurements linearly increased during the study in bulls from both groups. All bulls had a scrotal circumference larger than the minimum threshold value for cattle and high-quality semen. Study limitations/implications: The low availability of CLT bulls prevented the inclusion of a larger number of animals in the research. This low animal availability makes it necessary to establish standard values for testicular measurements and semen characteristics in the CLT breed in order to select the best individuals as sires and contribute to its conservation. Findings/conclusions: The CLT bulls had good scrotal circumference and semen quality from a young age and into adulthood. These traits make CLT bulls an important alternative for livestock breeding in the tropics.

Las biotecnologías reproductivas se utilizan para la conservación, expansión y mejora genética de bovinos y facilitan la creación de bancos de germoplasma de animales élite y razas en peligro de extinción. El objetivo del estudio fue comparar el efecto de dos dosis de hormona folículo estimulante en el comportamiento superovulatorio de hembras criollas Lechero Tropical (LT). El estudio se realizó en Veracruz, México, en un clima cálido. Se utilizaron 25 donadoras LT (47 ± 4 meses de edad y 423,9 ± 12 kg de peso vivo). Se utilizaron dos niveles de hormona folículo estimulante (FSH) de 260 (FSH1) y 210 mg (FSH2) por tratamiento. Las variables de respuesta se analizaron con un modelo lineal de efectos fijos. Los datos fueron procesados utilizando modelos generalizados con una distribución de Poisson. El peso y la edad influyeron en el número de cuerpos lúteos. El peso influyó en ovocitos no fertilizados, embriones degenerados y total de estructuras recolectadas. Solamente en ovocitos no fertilizados se encontró diferencia estadística (P = 0,004) entre tratamientos, pero no en cuerpos lúteos, embriones degenerados, blastocisto, embriones calidad uno, embriones transferibles y total de estructuras recolectadas (P > 0,05). Los tratamientos FSH1 y FSH2 indujeron similar número de embriones transferibles (2,7 ± 0,6 y 3,5 ± 0,7) y embriones calidad uno (2,5 ± 0,6 y 3,4 ± 0,7), por lo que la dosis de 210 mg de FSH1 sería la más recomendable para superovular hembras LT. Reproductive biotechnologies are used for the conservation, expansion and genetic improvement of cattle, and to facilitate the creation of germplasm banks of elite animals and endangered breeds. The objective of this study was to compare the effects of two different doses of follicle stimulating hormone (FSH) on the superovulatory behavior of Tropical Milking criollo (LT) females. The study was conducted in Veracruz, Mexico, in a hot climate. Twenty-five LT donors (47 ± 4 months of age and 423.9 ± 12 kg BW) were used. Two levels of follicle stimulating hormone of 260 (FSH1) and 210 mg (FSH2) were used for each treatment. The response variables were analyzed with a linear fixed effects model. The data were processed using generalized models with a Poisson distribution. The weight and age influenced the number of corpora lutea. The weight influenced the number of unfertilized oocytes, degenerate embryos and the total of collected structures. Only in unfertilized oocytes, statistical difference (P = 0.004) was found between treatments, but not so in corpora lutea, degenerate embryos, blastocyst, grade one embryos, transferable embryos and the total of collected structures (P > 0.05). The FSH1 and FSH2 treatments induced the same number of transferable embryos (2.7 ± 0.6 and 3.5 ± 0.7) and grade one embryos (2.5 ± 0.6 and 3.4 ± 0.7); the 210 mg dose of FSH1 would be the most appropriate for superovulating LT females. 146-152

In order to optimize the overall efficiency of pronuclear microinjection, we designed experiments to: 1) test the best developmental stage for transferring injected embryos to obtain pregnancies and transgenic pups; 2) determine the optimum number of injected embryos transferred to obtain pregnancies and transgenic pups; 3) investigate whether addition of non-injected embryos with injected embryos increased pregnancy rate (PR) and transgenic pups; and 4) establish the time during pregnancy of highest embryonic or fetal loss. Mice (CD1; 3 to 4 wk old), were superovulated with 10 iu PMSG and 5 iu hCG 48 h apart. One-cell embryos were collected for microinjection 20 to 24 h after hCG. The gene used was the whey acidic protein promoter linked to a coding sequence of the human protein C gene (WAP-hPC). Embryos were cultured in CZB at 37°C in 5% CO₂ in air. All the live pups born and embryos and fetuses recovered were analyzed by the polymerase chain reaction to detect the presence of the transgene. Experiment one consisted of nine transfer treatments (TRT) which included all the combinations of three developmental stages (1-cell, 2-4 cell and morula/blastocyst) with three quantities of embryos per transfer (15-24, 25-34 and 35-44). Ten transfers were performed for each TRT. The highest PR and total pups born (TOTP) were obtained after transferring 25 to 34 2-4 cell embryos (PR=90% TOTP=3.5/ pregnancy). However, overall analysis indicated that the percentage of transgenic pups born (%TRS) was highest using 1-cell embryos [33.9%, 20.0% and 11.1% for 1-cell, 2-4 cell and morula/blastocyst (mor/bl), respectively]. The second experiment consisted of six transfer TRT: 20-0, 16-4, 12-8,30-0, 26-4, and 22-8 injected - non-injected embryos, respectively (10 transfers/TRT). Data showed that PR and TOTP can be improved by addition of non-injected embryos. However, the percentage of transgenic pups was significantly (p< .05) higher when all the embryos transferred were injected (53.6 % vs 46.4 % for transfers without and with non-manipulated embryos, respectively). Additionally, 30 embryos per transfer yielded a significantly higher percentage (p< .05) of transgenic pups than 20 embryos per transfer (67.9 % vs 32.1 % for 30 and 20 embryos per transfer, respectively). In experiment three 45 transfers of microinjected embryos were performed (30 embryos per transfer). Fifteen recipients were sacrificed on day 4, 12, and 18 of gestation. On each day all embryos and fetuses were counted and analyzed for the presence of the transgene. The percentage of transgenic embryos or fetuses was not statistically different at any recovery day (45.8%, 35.5%, and 34.6% for days 4, 12, and 18, respectively). However, the number of viable embryos at day 4 was significantly greater than the number of viable fetuses on days 12 or 18 (10 ± 1.1,,5.1 ± 1.6, and 2.4 ± 1.3 for days 4,,12 and 18, respectively). Collectively, the results indicate that: 1) transfer of 20 to 30 1-cell embryos was the best method to obtain transgenic mice, 2) addition of non-injected embryos decreased the number of transgenic pups obtained per pregnancy, and 3) although most of the embryonic losses after microinjection happen before day 4 of gestation, additional losses occurred between days 4 and 18 of pregnancy. Ph. D.

El objetivo del presente estudio fue determinar la tasa de gestación en novillas Bos taurus x Bos indicus que reciben embriones producidos in vivo e in vitro, transferidos en fresco y desvitrificados.

El objetivo del trabajo consistió en determinar la asociación de tricomoniasis felina y bovina en UPP de la zona central del Estado de Veracruz.

El objetivo del presente trabajo fue determinar el efecto de dos métodos de criopreservación de tejido testicular bovino sobre la viabilidad espermática. Se obtuvieron testículos de 10 machos bovinos (1 testículo por toro) elegidos por conveniencia.

El objetivo del estudio fue determinar el efecto del temperamento sobre los niveles de cortisol y la tasa de gestación en vacas de doble propósito inseminadas a tiempo fijo (IATF) bajo diferentes índices de temperatura y humedad (ITH) en la zona centro del estado de Veracruz.

El objetivo de este estudio fue determinar y comparar las tasas de eclosión in vitro y de gestación obtenidas después de la transferencia de embriones bovinos vitrificados en pajilla 0.25 cc y en Cryotop®.

El objetivo de este estudio fue comparar la tasa de sobrevivencia y desarrollo in vitro posdescongelación de 60 embriones bovinos criopreservados por curva lenta o vitrificación y en ambos casos con y sin blastocelectomía. A 30 embriones se les realizó la blastocelectomía y a los restantes se les dejó intactos, de los cuales el 50% de cada grupo se criopreservaron por curva lenta y el remanente por vitrificación. Los embriones criopreservados por curva lenta fueron expuestos a 1.5 M de etilenglicol por 20 min y congelados a una velocidad de 0.5 °C/min en una congeladora automática. La vitrificación se realizó introduciendo los embriones en solución de equilibrio durante 10 min, después se pasaron por 4 gotas de solución de vitrificación durante 5, 5, 10 y 10 seg en cada gota, respectivamente, se colocaron en cryotops y se sumergieron en nitrógeno líquido. Posterior a la descongelación, los blastocistos se cultivaron en medio IVC3тм suplementado con 10% SSS durante 72 h a 38.5 ºC, en 5% CO2 y 5% aire...

El objetivo de este estudio fue comparar la curva lenta de congelación contra el métodode vitrificación en su eficiencia para criopreservar ovocitos de bovino. Se obtuvieron ovarios del rastro local y los folículos se aspiraron en TCM 199-HEPESpara la obtención de ovocitos...