title: In vitro maturation of equine oocytes obtained from different age groups of sexually mature mares.
abstract: Oocytes were harvested from mare ovaries obtained at slaughter and were divided into 3 groups based on the age of the donor. The age groups consisted of young (2 to 7 yr), middle-aged (8 to 14 yr) and aged (>or=15 yr) mares. There were no differences between age groups in the proportions of follicles available for examination or the proportions of normal, abnormal or total oocytes collected. After 24 h of culture, the overall maturation rate to the second metaphase (MII) was 52.7%. Maturation rates for oocytes obtained from young and middle-aged mares were similar, but oocytes from aged mares were only approximately 25% as likely to reach MII and they were 3 times more likely to remain at metaphase I. Twelve oocytes had chromosome spreads suitable for counting; 6 were haploid, 2 were hyperhaploid and 4 were hypohaploid. Insufficient numbers of readable spreads precluded comparisons of chromosome complements between age groups.
authors.affiliation: Department of Clinical Sciences, Cornell University, Ithaca, NY 14853, USA.
authors.forename: S P
authors.initials: SP
authors.lastname: Brinsko
authors.forename: B A
authors.initials: BA
authors.lastname: Ball
authors.forename: J E
authors.initials: JE
authors.lastname: Ellington