Timing Is Everything: Breeding Strategies and the Estrous Cycle
Part Two: Tests, Tips, and Breeding Options
By Arliss Paddock
Part one of this article took an overview of the bitch’s estrous or heat cycle, with a look at the physical and behavioral characteristics of its four stages: proestrus, estrus, diestrus, and anestrus. With the wide variation among “normal” bitches in both the outward signs and timing of cycling, dog breeders can be left guessing when trying to determine the best time to breed their bitch. Poor timing is the major cause of missed breedings.
Field Spaniels. Photo by Mary Bloom.
But thanks to scientific advances of the last two decades, breeders now have easy access to a number of new methods to help ensure breeding success. These include veterinary tests and procedures that can pinpoint ovulation and the optimal breeding day.
It’s important for the serious breeder to keep current with the range of breeding aids and options. Breeders can apply understanding of what happens during the bitch’s estrous cycle in considering both new and established tests and procedures.
When Help May Be Needed
Countless breedings have succeeded using the covering-all-bases approach: Once the bitch begins to stand for the male (begins “standing heat,” or estrus), breed the pair every other day until she’ll no longer allow it. This strategy has a good rate of success because spermatozoa survive in the bitch’s reproductive tract for up to seven days, so whenever the eggs are ready for fertilization it’s likely that live sperm will be there and waiting. This approach, if feasible, works with many bitches.
Other factors can come into play, however. The stud dog may not be available for an extended time, for example, or the bitch may be uncooperative. A variety of situations may call for reproductive veterinary assistance.
“If you own the male or can get an unlimited number of breedings, there’s nothing wrong with breeding the female every other day while she will stand for it,” says Dr. Margaret Root Kustritz, associate professor of small-animal reproduction at the University of Minnesota College of Veterinary Medicine. “I don’t advocate extensive workups on every breeding bitch. But for those with a history of missed breedings or reproductive-tract disease, and who are to be bred by artificial insemination, I strongly encourage veterinary intervention with techniques to assess the bitch’s most fertile period.”
Dr. Katherine Settle, a reproductive veterinarian practicing in Sanford, North Carolina, echoes that view. “There are cases where the behavior doesn’t match the timing,” she says. “Some bitches will never allow a male to breed; others will allow it at almost anytime during the cycle. The bitches that ‘don’t read the book’ are the ones that we need more help deciding when to breed.”
When Timing Especially Matters
Accurate timing is especially crucial for breedings that are to be done by artificial insemination (AI). Settle, who also breeds and exhibits Greyhounds and Black and Tan Coonhounds, provides canine reproductive services such as semen collection and AI. “Timing is more or less critical depending on whether the planned breeding is natural or using chilled or frozen semen,” she says. “Breedings using frozen or chilled semen will require different times of insemination, because of the reduced time of sperm survival.”
A guideline is that more manipulation of sperm equals shorter sperm-survival time, which equals more critical timing of insemination.
“Understanding of the cycle and the use of veterinary tests to determine the optimal breeding day are increasingly important as the spermatozoa are manipulated to a greater extent,” explains Root Kustritz. “When you breed by natural service or with fresh semen, the spermatozoa will live for up to a week, so if your timing is a bit off, you’ll still probably be okay. When you chill semen, you damage it a bit more; when you freeze and thaw it, you damage it quite a lot. That means your timing must be more precise.”
Some Key Tests and Procedures
Several types of tests and procedures can be performed before and during the heat cycle to assess reproductive health and pinpoint the ideal time for breeding.
• Brucellosis Testing
Whatever the planned breeding method, both the dog and bitch must first be tested for canine brucellosis, which causes pregnancy loss and infertility. Many breeders erroneously believe that brucellosis is mainly transmitted through breeding. In fact, the most common route is ingestion or inhalation of bacteria from the urine, vulvar discharge, or aborted materials of infected animals. “Any intact dog exposed to other dogs’ urine should be tested,” says Root Kustritz.
“Many breeders think that if the bitch or dog hasn’t been bred before, this test isn’t needed,” says Settle. “Think about it: Where do the largest numbers of non-neutered dogs congregate? At dog shows! Bitches should be tested before each breeding, and a stud dog at least every six months, or before each breeding if he is used less than every six months.”
She cautions: “False positives can occur with the type of brucellosis test done in your veterinarian’s office, called a RCAT or rapid card agglutination test. If this test result is positive, more tests need to be done. Do not euthanize a dog based on the result of your vet’s in-house brucellosis test!”
The hormones that are responsible for the outward signs of heat also cause dramatic physical changes in the vaginal walls. Your veterinarian can assess these changes by inspecting the vaginal tissues via a lighted scope, and this can aid determination of where the bitch is in her cycle.
• Vaginal cytology
Microscopic examination of cells sampled from the vaginal lining (epithelial cells) can help identify when a bitch in proestrus is nearing estrus. This test alone cannot be used to determine the ideal day for breeding, but it can help to indicate when it’s time to begin testing the blood for the levels of hormones that will signal ovulation.
• Progesterone and LH testing
During estrus, a sudden release of luteinizing hormone (LH) into the bloodstream stimulates ovulation to occur about two days later. Serum progesterone levels (that is, levels in the blood) begin to rise in a predictable way during and following this LH surge.
Testing the blood levels of both of these hormones together can serve to pinpoint the exact date of ovulation. The LH peak may be so transitory that it can go undetected, however, even with daily testing. Testing of serum progesterone levels is currently the most accurate and reliable method of identifying the time of ovulation. The progesterone level will be at about 2 ng/ml on the day of the LH surge and 4 to 10 ng/ml on the day of ovulation, and continues to rise after ovulation, remaining elevated for two months.
Because the newly released eggs must mature for 48 hours to be ready for fertilization, the optimal breeding day is two days after ovulation. “For fresh-semen breedings, whether natural or AI, I like to start breeding when the bitch’s progesterone reaches approximately 5 ng/ml,” says breeder-vet Dr. Phyllis Giroux.
“That level is consistent with ovulation. I will then have her bred every day or every other day until her vaginal smear [indicates] diestrus.”
Preparation Is Everything
Plan ahead, whether you will consult with your regular veterinarian regarding any reproductive tests or procedures, or seek the help of a reproductive specialist.
“Don’t wait until day 8 of the cycle to talk to your reproductive veterinarian,” advises Settle. “Call before or at the first signs of heat. Schedule an office visit to discuss the plan for the type of breeding you will be doing. When should you start any possible testing? Talk about potential problems, and plan what to do if they occur. For instance, if the bitch is ready to be bred on a Sunday, can the clinic do the breeding at that time?”
With knowledge, preparation, and a little bit of luck, the timing of your breeding—and everything else about it—will be perfect.
References and Further Reading
The Dog Breeder’s Guide to Successful Breeding and Health Management, by Margaret V. Root Kustritz, DVM, Ph.D. (Saunders, 2005): a very thorough, authoritative, and well-organized reference, extremely reader-friendly and easy to understand. Highly recommended for the serious dog breeder.—A.P.
Arliss Paddock breeds and shows English Cocker Spaniels and is former managing editor of the AKC Gazette.