Ask the Doctor.. Reabsorption of Puppies
From Eva Gomez of His Majesty's Mastiffs
Maybe you can touch on reabsorption in Mastiff bitches and why do they get pregnant the first time, but after that it's downhill?
Eva, your question was about reabsorption. The first thing I am going to comment on is pregnancy diagnosis, because very often breeders, and in some cases veterinarians, diagnose pregnancy based on very rudimentary estimations, including changes in behavior, color consistency of the nipples, the dietary preferences of the bitch, all subjective changes that both "feel" are related to pregnancy.
The bitch should be checked for pregnancy signs by abdominal palpation of the uterus at 28 days, or even better, an ultrasound performed using either a linear array or sector scan. The advantages of ultrasound are more than just accurately diagnosing pregnancy, but also identifying fetal status. The fetal heartbeats are detectable as early as 24-28 days after breeding and it is easy to determine by size, shape and the presence of the heartbeat the age of the fetuses. Radiography is also an important pregnancy monitor performed at approximately 50-55 days.
If, Eva, you have been performing ultrasound or abdominal palpation at 28 days and/or real time ultrasonography any time during the pregnancy and performing an x-ray at 50-55 days you will, indeed, be able to determine if your bitch is truly reabsorbing some or all of the puppies.
The most common time for this reabsorption to occur is between the 32nd and 44th day. In human beings it is normal for women to expel damaged fetuses, those that are -- from a chromosome standpoint -- abnormal or those that develop micro-abnormalities that are incompatible with continued development. Uterine disease is the second most common cause of reabsorption. There may be areas of the uterus that have begun to undergo a hormonally driven hyperplastic condition that is aggravated by the presence of low numbers of bacteria in the uterine tissue. E. coli is the most common bacterial contaminate of the uterine wall that is responsible for reabsorption. The herpes virus, mycoplasma species, b. hemolytic streptococcus species, are also agents which have been documented to cause reabsorption Another important part of maintaining good embryo health are the thyroid hormones. For bitches that you are going to put in your breeding program, Eva, it is important that you know the thyroid status as well.
One more category of agents that might produce an early embryonic death or a reabsorption are agents called teratogens. Teratogen is an agent that can induce a congenital defect when administered to a pregnant animal. There are three critical periods of development between conception and whelping. The pre- implantation stage which is from breeding until about the 19th day, the embryonic stage which the 19th to 35th day and fetal stage which is from the 35th day on to whelp. An embryo matures into a fetus and gross structural defects seldom occur except in structures undergoing rapid growth and maturation, such as the palate or the brain and parts of the heart and urogenital system. Agents that are used in veterinary medicine that have known teratogen capacities include carboyl (yes, that's the flea treat- ment); diazinon and dichlorvos (these are insecticides); fungicides such as mercuric chloride and griseofulvin; hormones such as progesterone; androgens which can cause masculinization of fetuses; corticosteriods even in small doses can cause cleft palate and late term abortions; phenobarbital or primidone which would be two drugs which individuals suspected of having a convulsive disorder might be taking on a routine basis. All will cause severe congenital abnormalities. In general, all drugs should be avoided for pregnant bitches, including vaccines unless they are absolutely necessary for the maintenance of the bitch's well-being. And, in my estimation, there are very, very few circumstances in which they would be even considered. The last category we should talk about if we are going to talk about a healthy pregnancy, is diet. For the pregnant bitch the maintenance of proper body conditioning and muscle tone is important for the six to nine months before the anticipated pregnancy. Overweight bitches have lower conception rates and have higher incidence of whelping difficulties. Supplementation with vitamins and minerals is important for the bitch, particularly in the last half of pregnancy. The composition of diet is very important. Protein levels 25% greater than the normal protein requirement for ordinary activity are necessary during pregnancy. Probably liver and/or raw meat, including chicken and turkey, make the best ways to increase the protein level. The carbohydrate needs, of course, increase too but only in a small way compared to the protein needs. Fatty acids are important in the latter half of pregnancy and a fatty acid supplement such a primrose oil has been very helpful. Raspberry tea leaves that contain large doses of trace minerals have been very helpful in maintaining uterine muscle contractility control during whelping.
Let's turn the question around and I am going to guess that your next question to me might be -- "well, how can I identify those bitches which are good candidates for breeding?" A guarded swab sterile culture should be done on the bitch between 7-10 months of age prior to her first estrus so that you can identify what her normal microflora is. Bitches that harbor (as a part of their microflora) e. coli or beta hemolytic streptococcus organisms (Type G & D), are subject to reabsorption; early embryonic death and stillbirths and neonatal deaths.