La producción de embriones in vitro es una de las biotecnologías de la reproducción animal que ha presentado mayor desarrollo en las últimas dos décadas; sin embargo, los resultados exitosos en estos procedimientos dependen de múltiples factores, entre ellos la presencia de especies reactivas de oxígeno, debido a que el proceso de fertilización in vitro y la manipulación de los gametos y embriones expone a las células a factores endógenos y exógenos que pueden afectar los mecanismos de defensa antioxidante y por consiguiente la calidad de los gametos y embriones. En esta revisión se discutirán algunas fuentes de especies reactivas de oxígeno, el uso de antioxidantes enzimáticos, no enzimáticos y polifenólicos para disminuir el estrés oxidativo en los procesos de producción in vitro de embriones, y su efecto sobre la calidad de los oocitos y embriones, la expresión génica y su competencia para el desarrollo embrionario.

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A microbiological analysis was performed to determine the frequency of isolation of microorganisms of infectious and environmental type in milk from a group of clinically healthy cows in two different types of milking (manual and mechanical). To each sample of milk was made bacteriological culture to determine the presence of microorganisms. Of 289 milk samples evaluated, 193 (66.78%) were positive for isolation of any type of pathogen, of which 81 (28.02%) samples came from manual milking and 112 (38.75%) belonged to mechanical milking, finding a higher percentage of isolation of bacterial pathogens in milks coming from mechanical milking system (p = 0.0236). The most isolated pathogen was the Arcanobacterium haemolyticum, A microorganism that forms part of the saprophytic flora of the animal, with an individual presence in 20.14% and in coinfection with other pathogens in 0.7% of the samples. The most common microorganism of subclinical mastitis in cattle is Streptococcus agalactiae, which in the present study was isolated from 12.50% of milk samples. The odds ratio (OR) between the isolation of Streptococcus agalactiae and the Somatic Cell Score (SCS) was determined, which was statistically significant, indicating that when this pathogen is present the SCS increases and the animals are more susceptible to mastitis.

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