Evaluation of canine and ovine oviducts for maturation of canine oocytes from antral follicles

Abstract

The goal of this study was to determine whether canine or ovine oviducts improve the maturation of canine oocytes obtained from antral follicles over an in vitro system. The objective of the first experiment was to evaluate the canine oviduct for its ability to promote maturation of canine oocytes obtained from the ovaries following spay surgery of the donor bitches. The objective of the second experiment was to evaluate ovine oviducts for their ability to mature similarly obtained canine oocytes. All oocytes utilized in both the first and second experiment were obtained from bitches in proestrus or early estrus. Immediately after the ovaries were collected from the spayed bitches they were placed in warm physiological saline solution and transported (3h) to the laboratory for retrieval of the oocytes. After retrieval, the oocytes were maintained in a warm Hepes buffered medium until being surgically transferred into oviducts or placed into the in vitro control culture medium. Of the 156 oocytes recovered from canine oviducts and adjusted for the number of ovulated oocytes, one matured to metaphase II (MII), seven matured to metaphase I (MI), and two had undergone only germinal vessicle breakdown (GVBD). The 198 in vitro control oocytes for canine replicates contained six that matured to MII, 11 that matured to MI, and six that underwent only GVBD. Transfer of canine oocytes into the sheep oviduct yielded three metaphase II oocytes, two MI, and three that underwent only GVBD out of 138 recovered. The 181 in vitro control oocytes for the sheep replicates contained 14 that matured to metaphase II, nine to MI, and six that underwent only GVBD. In conclusion, both the canine and ovine oviducts support the maturation of canine oocytes, but the level of maturation was not an improvement over the in vitro control. The maturation rate of canine oocytes in ovine oviducts was lower (p<.05) than the maturation rate of in vitro control oocytes. Incubating the extirpated oocytes in the dog oviduct provided no significant difference (p<.05) in numbers of oocytes matured to MII compared to in vitro controls.