Breeding always presents its challenges and we must not restrict our concern only to the genetic history that may give rise to the bad mouth or toyish head. We should also be concerned with the development of the fetuses themselves.
The incidence of abortion and resorption of canine fetuses is extremely difficult to assess because pregnancy cannot often be confirmed until about the 28th day. There are five known causes of both fetal resorption and abortion: fetal defects, resulting in early fetal death and resorption; abnormal maternal environment, usually resulting in the loss of the entire litter; infectious agents, i.e., Brucella; canine herpes virus infection, which may not affect the litter as a whole, but reabsorb or abort one or more fetuses; and trauma, which is extremely unlikely. All of these factors may cause both abortion and resorption, the biochemical dissolution or loss of tissue, in this case the fetus.
Abdominal ultrasonography is a reliable means of not only diagnosing pregnancy, but confirming the viability of the fetuses. In a litter of mine, we ultrasounded at 34 days, recognizing three fetal sacs and presumably three functioning hearts. In fact, a second ultrasonography and radiography at 55 days concurred, showing three spinal columns. Although we saw two heads, the third spine was lower in the abdomen, involving the organs, so my vet and I assumed there was a third head obstructed from view.
Finally, the night of the 65th day had arrived and the dam entered hard labor, whelped two bitches quite easily, and settled down to mother. I, of course, waited for the third pup, which never did arrive. Final radiography indicated what she had been telling me, that she was finished. Examination of the two delivered placenta proved unremarkable, exhibiting no abnormal traits.
Some months later at a canine behavior seminar I attended, Dr. Robert Walker, MRCVS, of the Centre of Applied Pet Ethology in the UK and one of the leading veterinary behaviorists, concurred with my opinion and that of my vet. It would seem that the cause of the "vanished" fetus could be attributed to a fetal defect(s). The fetus had apparently developed long enough to have completely or almost entire calcified before being enzymatically desynthesized. Fetal skeletal development cannot be seen until the 42nd to 52nd days after mating. Therefore, since we had viewed three spinal columns, my vet and I speculated that there may have been a problem in organ development or in the further calcification of the fetus, particularly the skull. Thus, whatever the case, the completion of the fetus's resorption, the skeletal elements, occurred between the 55th and 65th day of pregnancy. Thus, resorption had been occurring for some time.
Since whelping this interesting litter, the same dam has produced a healthy litter of four beautiful Norfolk pups and is the consummate mother.
ANTIC, December 1997
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