Produção in vitro de embriões em vacas das raças Nelore e Greyman: expansão das células do cúmulus de oócitos oriundos de folículos ovarianos, em diferentes dimensões, acompanhados ou não da presença de corpo lúteo (CL)

Abstract

The understanding of follicle growth and ovulation associated to physiological phenomenon is fundamental to optimize reproductive efficiency in the herd. Reproductive particularities between Bos indicus and Bos taurus must be taken into account when using ultrasound guided follicle trans-vaginal aspiration/ ovum pick up (OPU) in conjunction with produced in vitro embryo (PIVE). Successful OPU/PIVE depends on a variety of factors, as oocyte numbers per aspiration section; which influences the technique efficiency and characterizes the oocyte recovery rate per aspirated follicle. Thus, searching for physiological responses from cumulus oocyte complex (COCs) submitted to in vitro maturation; two experiments were performed: the first experiment evaluated the oocyte cumulus cells expansion from oocytes submitted to in vitro maturation after been obtained by OPU from ovarian follicles with different dimensions, in the presence or absence of corpus luteum (CL). Slaughter house ovaries were obtained and submitted to aspiration, classification, selection and oocyte maturation. Expansion images from cumulus cells were taken, and measured after 24 hours from start of maturation. The measures results, reflecting maturation, indicated the potential in aspirating follicles < 3mm, with better results when in absence of CL. These finding requires an exploration from OPU and its capability in terms of small follicles visualization, aspiration and oocyte recovery from sub utilized small follicles in the field. These follicles could add in OPU oocyte recovery, and possibly results in better PIVE index. In the second experiment, PIVE in Nelore (n=5) and Greyman (n=5) cattle breeds were compared. The cows were submitted to OPU every 30 days, with a total of three (n=3) OPU sections. Greyman cattle were recently introduced and adapted to North region of Brazil and the donor cattle from this breed presented a reasonable potential for PIVE. Despite of the fact that oocytes recovery rates in Greyman cows were not efficient as they were in Nelore cows, the in vitro fertilized (IVF) embryos indexes from Greyman were compatible with Nelore cow.