Planning Your Next Litter?
How do you insure that your bitch is bred at the right time to produce a litter? The old time method was to breed somewhere between the tenth and thirteenth day of her heat cycle. Or, when the vaginal discharge changes from red to amber, wait four days and breed her. This works for some, but is not by any means a sure bet for getting your bitch in whelp. Some simply breed the bitch on first acceptance and repeat, preferably four days later.
Determining the best time to breed
Hormone assays (progesterone tests) can be used when it is important to pinpoint the exact time of ovulation, such as when breeding with cooled or frozen semen, or when only one mating is possible. Progesterone testing is done by commercial laboratories, and any veterinarian can order the test and have results back the next morning. A series of daily tests may be required in some situations. However, these tests are expensive and not necessary in most situations.
A less expensive and highly accurate method used by many breeders is vaginal cytology. Smears taken from the lining of the vagina indicate the rise and fall of estrogen levels. The cells exfoliated from the surface of the vagina, when examined under a microscope, can be used to determine whether the heat cycle is normal, diagnose infection, prove or disprove a misalliance, or help determine the proper breeding time. Breeders can learn to do this at home (with the help of a book like Phyllis A. Holst, DVM’s “Canine Reproduction”) or it can be done by a veterinarian who specializes in reproduction. The smears cannot pinpoint the actual time of ovulation, but the bitch must be bred during the interval when the cells on the smear are completely cornified. If the stud is not in heavy demand, three breedings two or three days apart during this period should be nearly fool-proof.
Do not worry that the bitch will conceive puppies of different ages if breedings are spaced several days apart. The time of ovulation, with fertilization occurring three days later, determines the exact time of conception. Sperm deposited before the time of conception will survive in the vagina and be available when the ova mature and are ready to be fertilized.
Mating With More Than One Male
What if a bitch is accidentally mated to more than one male any time before the time of conception (maturing of the ova)? Just because a bitch was bred to the desired stud dog does not mean she is no longer in jeopardy of becoming pregnant by another unwanted dog. The sperm from both (or all) matings will live in the vagina for a number of days until conception occurs. Random chance determines which sperm fertilizes each ovum. Thus, the resulting litter could be sired by more than one male. However, it is not possible for an individual puppy to have more than one sire. Once a sperm penetrates an egg, a reaction of the egg’s outer shell blocks the entrance of any additional sperm after the first. If there is a question as to the parentage of the puppies, a DNA test performed after they are born should solve the problem.
Mismating or Mating with the Wrong Dog
Misalliances or mismatings contribute to the oversupply of unwanted puppies and can adversely affect the health and development of a young bitch. The first thing to do if you suspect a mismating is to determine if the bitch is in estrus and whether her vaginal smear is cornified. This should be done the same day, or within 24 hours at most. If the smear is not cornified, there is no need to worry that a fertile mating took place. If it is cornified, the second thing is to check for the presence of sperm. They can be seen on a wet smear for several hours after a mating.
The best solution to a misalliance of a pet bitch is to have her spayed. Ovariohysterectomy during pregnancy does not pose a significant risk to the bitch unless it is done very close to term and will prevent not only the unwanted litter but any chance of it happening again in the future.
If a purebred breeding animal is accidentally mated with a neighborhood dog or an undesirable male, a variety of hormones can be used to terminate the pregnancy. Prostaglandin F2alpha (PGF, Lutalyse(R), dinoprost tromethamine) is an effective treatment for termination of pregnancy in bitches. Properly administered, it is also safe and does not appear to have adverse effects on future reproductive performance of the bitch. According to Colorado State University, two other new drugs have shown promise as safe methods of terminating an unwanted pregnancy in dogs. Epostane inhibits steroid hormone synthesis by inhibiting the enzyme that converts pregnenolone to progesterone. It has been shown to terminate pregnancy in dogs after a 7-day treatment, and it appears to have this effect throughout gestation. Adverse side effects in dogs have not been been reported. Mifepristone (RU486) acts as a progesterone antagonist. Small clinical trials have demonstrated that this drug is very effective in terminating canine pregnancy after 25-30 days of gestation without apparent adverse effects.
Estrogens, however, are not recommended for use in terminating pregnancy in a bitch that you later want to use for breeding. Studies indicate there is a high risk of inducing uterine disease such as pyometra and some risk of causing a lethal aplastic anemia with these drugs.
There’s a lot more information on timing matings and other reproductive issues with dogs in Dr. Phyllis A. Holst’s book Canine Reproduction: The Breeder’s Guide. Holst is a veterinarian, researcher, and breeder and this is one of the most thorough and accurate books available for dog breeders.