The effect of oocyte size and bitch age upon oocyte nuclear maturation in vitro.

In vitro maturation in the bitch has yet to be fully investigated, and perfection of the technique is essential for future gamete salvage programs in endangered canine species. For optimal success with these techniques, knowledge of the individual animal and of oocyte effects upon maturational competence would be useful. Two factors were therefore studied using an aceto-orcein staining technique, which has been shown to be effective for monitoring nuclear maturation of canine oocytes following oocyte culture in medium supplemented with bovine serum albumin (BSA). Oocytes of different sizes were cultured in vitro and their nuclear maturation monitored. It was shown that the selection of oocytes which had acquired meiotic competence through adequate intrafollicular growth was important for in vitro maturation. In vitro maturation of oocytes from bitches aged 1 to 6 yr, and from those 7 yr and older was then compared, and it was found that oocytes from young bitches had a greater potential to mature than those collected from the older animals.