Fertilization rate and early embryonal development in female dogs (Canis familiaris – Linnaeus, 1758)

The objective of this work was to determine fertilization rates and embryonal recovery and to evaluate aspects of the early embryonal development. Eleven adult female dogs were used, with no defined breed. After the beginning of the natural estrus, these were mated and subjected to ovariohisterectomy on the 5th, 7th or 9th day postcoitus. Ovaries, tubes and uterine horns were separated. From the ovaries, the number of corpora lutea was determined. Tubes and uterine horns were washed separately in order to collect ovules and embryos, which were identified through the use of a stereomicroscope at 15x magnification. The fertilization rate was 94% and embryonal recovery 68.5%. On the fifth day, postcoitus embryos of up to eight cells were found in uterine tubes. Morulae or blastocysts were observed in uterine horns from the 9th day after recovery. On the basis of these results, it was concluded that the loss of structures can be due to the failure of their uptake by uterine tubes or during the execution of the technique. A high fertilization rate can be achieved even with the use of a single covering. It was also concluded that the embryonal development in uterine tubes had a duration of up to five days postcoitus with a stage of up to eight cells, embryos being found in stages of morulae in uterine horns nine days postcoitus.