Do season and previous motherhood affect how many mature eggs can be collected from dogs?

Details

Female dogs’ reproductive physiology, especially their gamete physiology, hinders successful in vitro maturation. Canine assisted reproductive techniques (ART) therefore depend heavily on oocytes matured inside the body. This study evaluated collecting these oocytes by flushing the fallopian tubes during laparotomy, and compared retrieval success by season and donor parity, or previous births.

The study used 124 female dogs: 39 in spring, 44 in summer, 25 in autumn, and 16 in winter. Average temperature and relative humidity were, respectively, 55.29 °F and 57.17% in spring, 75.67 °F and 72.83% in summer, 59.65 °F and 64.67% in autumn, and 33.55 °F and 58.67% in winter. The parity comparison used 18 dogs that had never given birth and 18 that had given birth multiple times.

Vaginal cytology and serum progesterone concentration were checked daily to determine ovulation timing. Laparotomy was performed under general anesthesia 72 hours after progesterone first reached at least 4.0 nm/mL, using the unit as printed in the abstract. Each fallopian tube was flushed with about 7 mL of TCM-199 supplemented with HEPES (Gibco, Grand Island, NY, USA).

After morphological assessment under a stereomicroscope, oocytes were denuded in 0.5% (W/V) hyaluronidase solution (Sigma, St. Louis, MO, USA) and stained with bisbenzimide (Sigma) at the concentration printed as “5 �g/mL” in the supplied abstract; the unit contains a corrupted character. Nuclear status was then examined under ultraviolet light. Based on nuclear stage, cumulus cell layers, and the color and homogeneity of the ooplasm, oocytes were classified as good, fair, poor, immature, or aged. Good and fair oocytes were considered usable for ART; poor, aged, and immature oocytes were considered unusable.

In vivo-matured oocytes could be collected throughout the year by fallopian-tube flushing. The average number collected per dog was significantly higher in spring (11.21 � 0.56) than in other seasons (7.88 � 0.63 to 9.27 � 0.35; P < 0.05). The characters between these numerical estimates and their accompanying values are corrupted in the supplied abstract and are retained here rather than interpreted. Autumn had a comparatively higher percentage of usable oocytes. The reported oocyte-recovery percentages were 74.67% in autumn, 67.51% in spring, 71.57% in summer, and 62.70% in winter; these differences were not statistically significant (P > 0.05).

The abstract reports that both oocyte number and quality varied with donor parity. Significantly more oocytes were collected from dogs with multiple previous births than from dogs that had never given birth: 10.4 � 0.54 versus 7.7 � 0.86, respectively, with the corrupted numerical separators retained as supplied. The usable-oocyte percentage was also higher in dogs with multiple previous births, at 70.75% versus 64.74%, but this difference was not statistically significant (P > 0.05).

The authors conclude that collecting oocytes produced and matured inside the body could provide a potential source of mature oocytes for canine ART.