Using Progesterone Testing to Determine the Right Time to Breed

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Ovulation timing, the telltale indicator that a brood bitch is ovulating and thus ready to breed, is the most common thing to go wrong in dog breeding. Poor timing during a bitch’s three-week heat cycle, also known as estrus, can cause a missed breeding and result in a normal female being labeled infertile.  

“Knowing when to breed is perhaps the most important aspect of breeding. The prime time to breed is 48 to 72 hours post-ovulation,” says Fran Smith, DVM, PhD, DACT, a board-certified repro-duction specialist, of Smith Veterinary Clinic in Burnsville, Minnesota. “This is because after ovulation, the released eggs continue to mature, reaching maturation two to three days later. Once the maturation process is completed, the eggs are ready for fertilization.” 

Progesterone testing is used to determine when a bitch ovulates and thus when to breed. A reproductive hormone, progesterone increases in the bloodstream just before ovulation. As the progesterone level increases, lutenizing hormone (LH) is released from the pituitary gland, triggering the release of eggs from the follicles. 

“When progesterone reaches 5.0 to 10.0 nanograms (a measure of one billionth of a gram) per milliliter of blood, a bitch is ovulating,” Dr. Smith says. “The sooner the progesterone results are known, the better, since timeliness is so important in breeding.” 

In her veterinary clinic, Dr. Smith uses a progesterone test that produces results in one hour based on chemilumenescence, or a process in which light is emitted from chemical reactions. The gold standard is radioimmunoassay (RIA) testing, which detects the quantitative progesterone level, though RIA testing is typically only available in veterinary teaching hospitals or large reference laboratories. At-home progesterone kits are available that estimate progesterone levels through color changes, though these are not as accurate as chemilumenescence or RIA progesterone testing. 

Breeders can combine progesterone testing and behavior monitoring to help pinpoint the best time to breed a bitch. Knowing when a bitch ovulates as detected by progesterone testing significantly increases the chance of a successful breeding. 

“Once you have confirmed ovulation with progesterone testing and know when to breed, you are more likely to get a larger litter size,” says Dr. Smith. “You also will know that a bitch’s due date is 62 to 64 days later.” 

Signs a Bitch is Ready To Breed

  • A pinkish, reddish discharge appears during the first week of the heat cycle that gradually turns a tan color during fertility, though some bitches have reddish discharge throughout estrus 
  • The vulva, or two thick folds of tissue at the outer portion of the female reproductive tract, will be swollen and soft at the peak of the heat cycle 
  • Tail flagging, a behavior in which a female stands still while a male investigates her vulva, even wagging her tail from side to side to help a male pick up on her scent, is common 
  • Moody, sensitive behavior, including whining, is common before estrus 
  • Males become keenly interested when they smell the change in a female’s hormones, an indicator she is in her optimal fertile period and ready to breed 

Feeding During Pregnancy

During pregnancy a bitch must not only meet her own maintenance energy requirements but also those of the growing fetuses. The amount of food she is provided should be gradually increased during the nine weeks of pregnancy. 

The increased energy demand is minimal during the first five weeks of pregnancy due to the small mass of fetal tissues. Feeding her typical caloric intake of a dog food formulated for growth or all life stages is best during this time.   

As the pregnancy progresses beyond the fifth or sixth week, the rapid rate of fetal tissue growth leads to a significant increase in a bitch’s energy requirement. It is estimated that her energy requirement will increase approximately 10 percent per week from week six to week nine. Thus, at whelping a bitch’s energy requirement may be nearly one and a half times greater than her typical maintenance requirement.  

During the last three weeks of pregnancy, a brood bitch should be fed two to three times more than before pregnancy. Small feedings throughout the day of a caloric-dense diet, such as one of the Purina Pro Plan puppy foods or an all life stages food, is recommended. A puppy food also is recommended for the first part of lactation. Regardless of the phase of pregnancy, diets should be adjusted based on maintaining an ideal body condition for the pregnant bitch. 

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