Sp. Brinsko et al., IN-VITRO MATURATION OF EQUINE OOCYTES OBTAINED FROM DIFFERENT AGE-GROUPS OF SEXUALLY MATURE MARES, Theriogenology, 44(4), 1995, pp. 461-469
Oocytes were harvested from mare ovaries obtained at slaughter and wer
e 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 (gre
ater than or equal to 15 yr) mares. There were no differences between
age groups in the proportions of follicles available for examination o
r the proportions of normal, abnormal or total oocytes collected. Afte
r 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
similar to 25% as likely to reach MII and they were 3 times more like
ly to remain at metaphase I. Twelve oocytes had chromosome spreads sui
table for counting; 6 were haploid, 2 were hyperhaploid and 4 were hyp
ohaploid. Insufficient numbers of readable spreads precluded compariso
ns of chromosome complements between age groups.