title: Developmental competence of oocytes from prepubertal Bos indicus crossbred cattle.
abstract: The aim of the present study was to evaluate the effect of age on embryogenic competence of oocytes recovered from Bos indicus crossbred calves and heifers. Cumulus-oocyte complexes (COCs) were collected from 4- to 7-month-old calves (experiment 1) and from 9- to 14-month-old heifers (experiment 2) during processing at an abattoir. In both experiments cow COCs were used as control. COCs were in vitro matured and fertilized, and the presumptive zygotes co-cultured with cumulus cells until 224 h post insemination (hpi). In experiment 1, the development rate during the first 68-72 hpi was similar (P > 0.05) between embryos derived from calves and cows. Fewer embryos from calves developed to the blastocyst stage, resulting in a lesser blastocyst production as well as lesser hatching rate (P < 0.05). The embryo development after blastocyst stage was, nevertheless, similar (P > 0.05) between blastocysts derived from calves and cows, suggesting that the development after blastocoele formation is not compromised in embryos derived from calves. In experiment 2, there were no differences (P > 0.05) on cleavage, blastocyst and hatching rates between embryos derived from prepubertal heifers and cows. The rate of blastocyst development until hatching was also similar (P > 0.05). These results indicate that oocytes from 9- to 14-month-old B. indicus crossbred heifers have the same developmental competence as oocytes derived from cows, while ocytes derived from 4- to 7-month-old B. indicus crossbred calves are less competent in developing to the blastocyst stage in vitro. It suggests that oocyte competence in B. indicus crossbred cattle is achieved around 9-14 months of age.
authors.affiliation: Embrapa Dairy Cattle Research Center, Rua Eugênio do Nascimento, 610, Juiz de Fora, MG 36038-330, Brazil. camargo3112@hotmail.com
authors.forename: L S A
authors.initials: LS
authors.lastname: Camargo
authors.forename: J H M
authors.initials: JH
authors.lastname: Viana
authors.forename: W F
authors.initials: WF
authors.lastname: Sá
authors.forename: A M
authors.initials: AM
authors.lastname: Ferreira
authors.forename: V R
authors.initials: VR
authors.lastname: Vale Filho
mesh_terms: D000375:Aging; D000818:Animals; D001755:Blastocyst / Q000502:physiology; D002417:Cattle / Q000235:genetics*; D003433:Crosses, Genetic; D005260:Female; D005307:Fertilization in Vitro / Q000662:veterinary; D009865:Oocytes / Q000254:growth & development*; D012741:Sexual Maturation; D046509:Tissue Culture Techniques