Dr. Jenna Dockweiler, MS, DVM, DACT, CCRT, CVAT Veterinary Geneticist at Embark Veterinary, presented her session Responsible Breeding Practices at the second annual 2022 Embark Canine Health Summit.
This informative discussion reviews the breeding candidacy of the dog and responsible breeding as well as Brucella canis, and its management in a breeding setting. You’ll also learn about the estrous cycle, progesterone testing, and breeding management of the bitch. In addition, you’ll receive an overview of eutocia (normal whelping) of the bitch.
What makes dogs ideal breeding candidates? When setting out to breed dogs, the goal is for each generation to improve upon the last. A responsible breeder will ensure there are homes for all the puppies before breeding and will mandate sterilization of pet-quality offspring. Breeders are responsible for the puppies they produce for each offspring’s lifetime. They should also provide adequate socialization and exposure to unique situations for the puppies before they go to their new homes. They will also be partially crate trained, on their way to being potty trained, and will have been introduced to new experiences such as climbing stairs and walking on different surfaces.
A list of phenotypic (hips, eyes, patellas, elbows) and some genetic health tests as recommended by each breed’s parent club are listed by the Orthopedic Foundation for Animals (OFA). This is a public database but is only as good as the results posted by dog owners. Responsible breeders should be transparent with all their test results.
For hips, breeding stock must be 2-years-old to receive a final score. At OFA, hip scores are calculated through a consensus opinion among three radiologists, and each dog gets a qualitative score. To take the x-rays, there is usually no sedation required. However, these tests do not measure laxity, which is the underlying cause of hip dysplasia.
Another hip test is the Pennsylvania Hip Improvement Program (PennHIP), which tests for hip laxity. All dogs are born with normal hips, but some are looser than others, and this test measures how far the ball is able to be pulled from the socket. Three x-rays are taken of the dog’s hips: extended VD (“OFA view”), compression, and distraction. A distraction index is then calculated. Results are a numerical value compared to other individuals of the same breed. There are downsides such as the high cost, heavy sedation needed, and there is no public database. The distraction index doesn’t change during the dog’s life, which means pups as young as 16-weeks-old can be tested.
Genetic Health Testing
Genetic health testing is important for identifying alleles that cause disease. Knowing the at-risk or carrier status of breeding stock helps make informed breeding decisions. For example, a breeder can still be breeding carriers to clear dogs to reduce the incidence of diseases and at the same time not lose genetic diversity.
There are three types of genetic health test results:
- At-risk is two copies of autosomal recessive alleles; 1 copy of a dominant/codominant allele; or 1 or 2 copies of x-linked, depending the mode of inheritance.
- Carrier is one copy of autosomal recessive allele; 1 copy of x-linked recessive in females.
- Clear means no copies of the disease allele
Some genetic testing platforms can determine the genetic coefficient of inbreeding (COI). This COI test is more accurate than a pedigree COI which only goes back 5 to 10 generations and assumes there are no earlier relatives. In reality, you can’t start from zero, as most founders of a breed are related to one another to some degree.
Brucella canis is a bacteria that causes infection in dogs and humans. It’s mandatory to test your bitch and stud dog before breeding. It was first discovered in 1966 with unexplained abortions in a Beagle kennel. Transmission comes from contact with body fluids including saliva, tears, urine, reproduction secretions, and semen.
The bacteria penetrates the mucus membrane and can travel to lymph nodes, the spleen, and the liver. It will show up in about 2-4 weeks in a blood culture post-infection. The bacteremia typically persists for weeks and is intermittent after that. It targets the reproductive tissue.
Signs and symptoms in bitches include later term abortion, early embryonic death, birth of weak/stillborn pups, normal pups that will develop the disease later in life, or they can be asymptomatic. In dogs symptoms can include epididymitis, scrotal edema, scrotal dermatitis, teratospermia infertility, or infected animals can be asymptomatic.
The diagnosis is best made with a culture of either blood, semen, urine, or aborted tissues. It’s fastidious and slow-growing and the culture needs to be sent to a special lab to grow. It’s prevalence is hard to say; sources have found as low as .4% among hobby breeders and as high as 9-83% among commercial breeders. In one study on shelter dogs in Mississippi, 35% of shelters housed positive dogs. In these positive shelters, about 17% of dogs were positive.
Treatment is not recommended. The goal is remission, and relapse is common, All positive animals must be spayed/neutered, and a long course of antibiotics is used to try to eliminate the bacteria. In many cases, the bacteria can “hide” in the lymphoid tissue and be impossible to kill completely despite antibiotic administration.
It’s important to test all new arrivals to a breeding program, and to test breeding dogs every six months. Even with artificial insemination there can be transmission since semen extender may not kill the bacteria, and it can survive freezing. There is no vaccine available. Brucella canis is out there, which is why breeders need to keep testing breeding dogs.
The Estrous Cycle
There are four stages of the canine estrous cycle: proestrus, estrus, diestrus, and anestrus. Hormones involved with determining the optimal timing for breeding involves measuring estrogen, luteinizing hormone (LH), and progesterone. Most bitches cycle twice per year. There are some exceptions including Basenjis and Mastiffs among others, which cycle only once per year, but most bitches will come into season about every 6 to 12 months.
During proestrus there will be a bloody discharge, vulvar swelling, the attraction of a male, and playful behavior from the bitch, but she will not allow any mounting from the male. This stage lasts approximately 9 days, with a published range of 6-11 days. Estrogen is dominant and will peak 1-2 days before estrus.
When in estrus the bitch will stand for breeding, flagging her tail, and be receptive to males. Text books will tell you a straw-colored discharge will appear, but some individuals have bloody discharge throughout their heat cycle. This stage also lasts an average of 9 days, but it could last anywhere from 1-20 days. In this stage, the LH surge occurs. After the surge, ovulation will occur between 24-48 hours later. Progesterone (P4) at ovulation is 4-6 ng/mL (as measured on a reference lab enzyme immunoassay) and continues to rise.
During the dietrus stage progesterone levels increase for 2-3 weeks, then plateau for an additional 1-2 weeks, then wane over the next 10-30 days. The anestrus stage occurs after a pregnancy, a false pregnancy, or a normal estrus cycle. It lasts at least 90 days. If heat cycles occur more frequently than every 4.5 months or so, infertility can result due to lack of sufficient endometrial repair.
Watch Dr. Dockweiler’s full session:
A breeder and their veterinarian will typically start monitoring hormone levels of the bitch 3-5 days after the breeder notices spotting (bleeding) from the vulva. Ideally, bitches should be monitored every 2-3 days via progesterone testing, vaginal cytology (looking at cells under a microscope), and vaginoscopy (using a scope to visualize the vaginal canal).
Serial monitoring is essential since the behavior of a bitch can be unreliable. Bitches can be in estrus for 20 days, and not yet fertile. Male behavior is also often not a great indicator of peak fertility since they get excited if the bitch smells different for any reason (such as due to an ear infection).
- Progesterone timing baseline is <1 ng/mL, LH peak 2-2.5 ng/mL Ovulation 4-6 ng/mL (as measured on a reference lab enzyme immunoassay).
- Ideal time to breed is 4-7 days post-LH peak; ovulation occurs approximately 48 hours after LH peak.
- An oocyte (an egg) takes at least 48 hours to mature after ovulation, so it makes no sense to breed for two days after the LH peak.
- Breeding times can be more flexible with fresh or fresh chilled semen because semen is viable for much longer when compared to frozen.
- With frozen semen you have to wait as long as possible after the LH surge to breed, about 7 days, because frozen semen is only viable for about 12 hours after thawing. This way, there will be more mature eggs waiting to be fertilized.
- The number one reason for missed matings is poor timing of breeding.
Testing progesterone levels is also useful for the estimation of the due date.
- LH peak 65 +/- 1 day.
- Ovulation 63 +/- 1-2 days,
- Cytology (day 1 diestrus) 57 +/- 3 days, a wider window but better than no information at all
- If all you have is the breeding date, 63 +/- 7 days is all you have to guess when she is due to whelp.
- Knowing estimated due dates helps to know if the bitch is overdue and may be in trouble. Semen is hardy in the bitch and can survive for many days with no decrease in concentration or quality.
Artificial Insemination can be done vaginally with a MAVIC catheter which has a balloon on the end to simulate a tie or an AI catheter. Since frozen semen can’t get through the cervical barrier well, it must be inseminated into the uterus directly. This can be accomplished by a transcervical insemination or surgical insemination.
Vaginal cytology (looking at cells under a microscope) is helpful in estimating the due date, 57 +/- 3 days from day 1 diestrus. It helps to determine the time of estrus if no male is present and signs are limited. You can follow changes in bitches with subfertility using this method.
The vaginal epithelium increases in thickness from a few cells in early proestrus to 20 to 30 cells at the end of proestrus due to estrogen. In proestrus there will be increased cornification of cells moving further away from the blood supply. Cells that are round and happy are near their blood supply, the farther they move away they begin to have sharp edges and pyknotic nuclei.
During estrus they will be 90-100% cornified looking at them under the microscope and furthest from the blood supply. During diestrus, there is a sharp decrease in the percentage of cornified cells, by about 20% – 50%. It’s typically not subtle! During anestrus there are no cornified cells.
Vaginoscopy involves using a scope to look at the vaginal canal. Hormonal changes alter the fluid retention properties of the mucosa (moist, inner linings) and can be used to define critical time points in the estrus cycle. During proestrus there are two stages of changes: folds become edematous (swollen with fluid) and later shrink. During estrus shrinkage of vaginal mucosa will intensify. By the end of estrus, folds are maximally shrunken and angulated (crenulated). During diestrus you will see a rounding out and smoothing of the vaginal mucosa. During anestrus the mucosa is thin, flat, and susceptible to trauma.
Ultrasound is the gold standard of diagnosis. You can see embryonic vesicles on day 21-23, heartbeats on day 24-25, placentas on day 28, and fetal movement on day 35. Radiography is used as early as day 45, though fetuses are typically easier to see and count later in gestation (day 60). You can also use the Relaxin test on day 30 or an abdominal palpation on day 25. Caution must be used with abdominal palpation, as pyometra occurs during the same timeframe as pregnancy (in relation to the heat cycle) and can have a “string of pearls” feel.
Approximately 60% of puppies are delivered in a cranial presentation (head first). The remaining 40% are delivered in caudal presentation (feet first with all 4 limbs extended), which is not to be confused with a breech position. In a breech position the hips must also be flexed forward.
- Stage I parturition begins when uterine contractions start. It ends when the cervix is fully dilated. On average this stage takes 6-12 hours, and up to 24-36 hours is possible (especially in maiden bitches).
- Stage II begins with the complete dilation of the cervix and ends with the delivery of a fetus. Each pup should take about 30 minutes to deliver. If a pup takes longer than 30 minutes to deliver, then that is cause for concern.
- Stage III begins after the expulsion of the fetus and ends with the expulsion of the placenta. Stages II and III occur simultaneously. Sometimes puppies and placentas may come out separately. Try to get the placenta away from the bitch after it’s removed from the puppy because there is no known benefit to her eating them and it can give her diarrhea.
Once puppies are born they need to keep warm with a contact temperature that is at least 85 to 95 degrees F. It’s best to use a heating pad versus a heating lamp, because overhead lamps tend to dehydrate puppies. It is vitally important puppies are able to escape this heat source easily if they become too hot. Puppies need to nurse within the first 6 hours of birth because they will exhaust their brown fat reserves in this timeframe, and they need colostrum from the mother for immunity. Newborns need access to milk every two hours. Weigh puppies daily. They should gain 5-10% of their birth weight each day. One common mistake is to use daily weight, not birth weight, when calculating the growth.
Learn more about responsible breeding practices, Canine Reproductive Emergencies, and other topics featured at the Second Annual Embark Canine Health Summit and sign up for 2023.