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Ovarian follicular dynamics, follicle deviation, and oocyte yield in Gyr breed (Bos indicus) cows undergoing repeated ovum pick-up
- Viana, J.H.M., Palhao, M.P., Siqueira, L.G.B., Fonseca, J.F., Camargo, L.S.A.
- Theriogenology 2010 v.73 no.7 pp. 966-972
- cows, Gir (cattle breed), zebu breeds, assisted reproductive technologies, oocytes, cumulus oophorus, extraction, frequency, ultrasonography, animal performance, female fertility, ovarian follicles, follicular development, oogenesis, embryo (animal), viability, yields, zebu
- The objective of this study was to evaluate ovarian follicular dynamics during intervals between successive ovum pick-up (OPU) and determine its effects on the number and quality of recovered cumulus-oocyte complexes (COCs) in Zebu cows (Bos indicus). Pluriparous nonlactating Gyr cows (Bos indicus; n =10) underwent four consecutive OPU sessions at 96-h intervals. The dynamics of ovarian follicular growth between OPU sessions was monitored by twice-daily ultrasonographic examinations. A single dominant follicle (DF) or two codominant (CDF) follicles (>9mm) were present in 63.3% (19 of 30) of intervals studied, with follicle deviation beginning when the future dominant follicle (F1) achieved a diameter of 6.2±0.3mm. The phenomenon of codominance was observed in four (13.3%) of the inter-OPU intervals. The remaining intervals (36.6%, 11 of 30) were characterized by a greater follicular population, lower rate of follicular growth, and a smaller diameter F1 (P <0.0001). There was a tendency (P =0.08) toward an increase in the number of recovered COCs when dominant follicles were not present (NDF). The quality of COCs was not affected by the presence of a single dominant follicle, but codominant follicles resulted in recovery of a lower proportion of viable embryos (40.0%, 62.1%, and 63.6%; P <0.05) and higher proportions of degenerate COCs (56.0%, 30.3%, and 28.6%; P <0.05) for CDF, NDF, and DF respectively. We concluded that, in Zebu cows, (a) repeated follicle aspirations altered ovarian follicular dynamics, perhaps by increasing follicular growth rate; (b) follicular dominance could be established in cows undergoing twice-a-week OPU; and (c) the presence of a dominant follicle during short inter-OPU intervals may not affect COC quality, except when a codominant follicle was present.