Mustard & Pepper Summer 2024

Taking The Guesswork Out of Dog Breeding with Progesterone Testing AKC Breeder Symposium, Columbus, Ohio Gail McRae, DVM

A ccuracy in timing a dog breeding using progesterone testing can help achieve efficiencies in litter production. In other words, knowing the right time to breed a female in estrus, or in heat, is a cornerstone of good breeding management. “Progesterone increases in a predictive manner, so we can use it to determine the important landmarks for breeding, such as the LH surge, ovulation and the fertile window,” says Gail McRae, DVM, who is completing a theriogenology residency at The Ohio State University College of Veterinary Medicine. She presented on progesterone testing at the AKC Breeder Symposium last fall in Columbus, Ohio. A reproductive hormone, progesterone, increases in the female’s blood prior to ovulation. As the progesterone level increases, another hormone, luteinizing hormone (LH), is released from the pituitary gland, stimulating the release of eggs from the follicles and triggering ovulation and the further rise in progesterone. The eggs mature in around 48 to 72 hours and thus become ready to be fertilized by sperm. “Progesterone is the only way we truly know when a female is ready to be bred. It also helps narrow down the whelping date to 63 days plus or minus one day from ovulation or 65 days plus or minus one day from the LH surge,” explains Dr. McRae who is also completing a master’s degree in which she is studying infertility in females. Breeders may opt to work with reproduction specialists who are boarded in theriogenology or veterinarians with a special interest in reproduction for best practices in dog breeding. Particularly when using frozen semen veterinary reproduction specialists can help determine the ideal time to breed for best outcomes. “The semen type dictates the right time to breed. Fresh semen on average lasts over 48 hours, chilled semen lasts about 48 hours, and frozen semen lasts 12 to 24 hours. If we are doing a frozen semen breeding, we usually wait until day three or four

post-ovulation to breed a female to ensure the eggs are mature. We want the progesterone level to be around 15 nanograms per milliliter in the blood,” Dr. McRae says. “If we are using fresh or chilled semen, then we breed during post-ovulation on days one and three or on days two and four. We also can breed one time on days two to three post ovulation for best results. This is because the sperm is viable for five to seven days and because it takes the eggs around two days to mature prior to fertilization. The rate of maturation of the eggs differs based on the amount of progesterone present.” At Ohio State, the theriogenology team uses an Immulite machine to determine the progesterone level in females. The two-hour Immulite progesterone test relies on a method called chemilumenescence to pick up the presence of certain enzymes and provide a quantitative level of progesterone. “We recommend that breeders work with their veterinarian and have their blood samples sent out to a diagnostic testing laboratory to be tested on an Immulite machine to ensure accurate, comparable results,” Dr. McRae says. “Although there are many different progesterone-testing machines, some

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Summer 2024