The inability of a female dog to become pregnant or to carry a pregnancy to term is a top concern of breeders. A plethora of causes could contribute to a female’s failure to produce a litter of puppies.
“Ninety-five percent of the consultations I do relate to poor breeding management. It is the number one reason for infertility,” says Andrea Hesser, DVM, DACT, a board-certified veterinary reproduction specialist, who practices at the Animal Medical Center of Richardson (Texas).
Miscalculated heat cycles, infertile stud dogs, breeding too soon between pregnancies and lack of genetic testing are examples of breeding management errors that can sidetrack canine pregnancy. Reproductive health issues involving uterine infection, inflammation and cysts can also shortchange a female’s pregnancy success.
“For a lot of dogs, we don’t know or can’t document exactly why they didn’t get pregnant,” Dr. Hesser says. “Failed fertility sometimes is simply due to breeding timing.”
Problems Conceiving
“Breeding timing is closely tied to the luteinizing hormone (LH) surge and the rise in progesterone, which trigger ovulation and pinpoint the fertile window in which to breed. Most females ovulate around 2 days after the LH surge,” Dr. Hesser says.
“We want to see a 3 ng/mL (nanograms per milliliter) rise in progesterone over 24 hours to confirm ovulation,” she says. “You may not realize a female has ovulated if you are not taking blood samples to test progesterone. The peak fertile period is from 2 to 4 days following ovulation.
“Other factors, or combination of factors, could affect conception. The breeding technique used [see “Breeding Technique Considerations,” at bottom left], oocyte (egg) viability, semen quality and incompatibility between the breeding partners are examples,” Dr. Hesser says.
“Although a female will cycle her whole life unless there is an underlying health condition like an ovarian tumor, they sometimes don’t make healthy oocytes when they are older,” she says. “Age can be a reason for a lack of conception.”
Likewise, “once an immature oocyte is fertilized, the ability of an oviductal embryo to navigate and attach within the uterus from day 6 to day 12 of gestation is very important,” she says. “Sometimes the embryo cannot grow. It may be next to a cyst in the uterus blocking access to the blood supply that provides nutrition from the mom.”
A stud dog’s potency as a producer is essential for successful pregnancy.
“The only way to truly verify his fertility is if that dog has recently had litters,”
–Dr. Andrea Hesser
“A semen evaluation assesses a stud dog’s reproductive health by measuring sperm motility, morphology and concentration,” she advises. “Heat stress, obesity, aging and some medical conditions can cause oxidative stress and affect all three measures.”
Partner incompatibility occurs when “some stud dogs and some females just don’t get pregnant,” Dr. Hesser says. “In contrast, some stud dogs are natural breeders with innately high fertility that would be very good at improving your outcomes.”
Inflammation & Infection Issues
“The most common causes of uterine health problems involve inflammation, cystic changes, fibrosis, or scar tissue in the uterine cells that inhibits nutrition, and a lack of uterine rest by breeding before 6 months between cycles,” Dr. Hesser says. “Some females are affected by more than one disorder.
“Low-level inflammation in the uterine tissues is common during pregnancy, making it the No. 1 suspect when there is a problem,” she says.
An example is lymphocytic plasmocytic endometritis, a chronic inflammation of the uterine lining linked to hormonal fluctuations during the heat cycle. The condition is attributed to difficulty getting pregnant and having singleton puppies or small litters.
“Inflammatory endometritis can be treated with a low-dose steroid protocol 6 to 9 weeks before the heat cycle,” Dr. Hesser says. “It is especially effective in females with regular heat cycles where you can estimate when to begin the treatment to get the best effect.”
Endometritis can be a precursor to pyometra, an infection of the uterus often caused by E. coli bacteria. Pyometra is one of the most common reproductive emergencies and is especially dangerous when it leads to sepsis, endotoxemia or uterine rupture.
“The immune system is naturally suppressed during pregnancy because the body is trying not to reject its own offspring and other uterine inhabitants,” Dr. Hesser explains. “Thus, a female is more susceptible to infection during pregnancy. If she is immune challenged during pregnancy, something she can typically handle can become a recipe for loss.”
Resorption of fetuses and fetal loss during pregnancy relate to uterine irritability, which may occur secondary to another cause. Infection from pyometra, exposure to pathogenic bacteria from a raw meat diet or poor dental health can play a role.
“If you have fertility issues, you should avoid feeding a raw meat diet during pregnancy,” Dr. Hesser says. “Bacteria likes to go to the uterus, thus a dog is more susceptible during pregnancy just like a person who may avoid certain foods during pregnancy specifically.
“The same is true for dogs with unhealthy dental care in which bacteria becomes systemic in the body. Breeders should manage a dog’s oral care before breeding and stay on top of it.”
Premature low-level uterine contractions also can flare uterine irritability.
“This can be a genetic condition,” she says. “If contractions are not monitored, such as by using a WhelpWiseTM system and drugs to calm the uterine contractions that are occurring, it can cause progesterone to decline to the point progesterone supplementation is needed to carry the pregnancy.
“Low progesterone also can occur by trauma from illnesses such as heat sickness, tick disease or general infection. Almost all things that result in fetal stress will cause progesterone to drop.”
Dr. Hesser says, “The dog is remarkable at hanging onto litters once she’s pregnant. By addressing red flags of concern along the way, you can potentially circumvent a problem from becoming a roadblock to a healthy pregnancy.”
Breeding Technique Considerations
“The technique used in breeding impacts the placement of semen in the female’s reproductive tract and ultimately pregnancy. Transcervical insemination (TCI) and surgical artificial insemination (AI) deposit semen directly into a female’s uterus; vaginal AI places semen in the vagina requiring sperm to navigate the cervix and uterus to reach the oviducts for fertilization.
The breeding protocol and semen type also influence fertility. One method is to breed a female starting 1 to 2 days after ovulation and breeding every 24 to 48 hours using a combination of TCI and natural breeding or TCI and vaginal AI with fresh or chilled semen during her fertile window. Fresh semen typically lives 5 days or longer in the uterus and oviducts, and fresh chilled semen lives up to a week or more. Frozen semen survives 12 to 24 hours after thawing and requires either TCI or surgical approaches for success.
