By Gary M. Greene, DVM, DACT
The use of artificial insemination in the dogs has experienced a tremendous increase in popularity over the last several years due to both its increased success rate and the flexibility it allows the dog breeder. A stud dog can be utilized successfully and easily from thousand of miles away, allowing the breeder to choose the best genetics for his or her bitch without the risks, expense, and other difficulties associated with transportation of the bitch. A previous or current champion’s genetics can be preserved indefinitely through the use of frozen semen. There are several factors that determine the success or failure of artificial insemination. The most important of these factors is proper timing of the insemination.
Old rules of thumb such as breeding between days 10 to 14 will not work in every case because of the variable length of standing heat (receptivity) and because the optimum time to breed may occur any time during, before, or after standing heat. Vaginal smears have been used to help diagnose the proper time to breed. They are most helpful as a rough guide to the stage of proestrus or estrus when using natural service. But they are not accurate enough to use alone when utilizing fresh chilled or frozen-thawed semen.
A more exact method to properly time insemination is to measure serum progesterone levels. During estrus, progesterone levels are as low as 0-2 ng/ml early on, rise to levels of 2.0-2.9 ng/ml during the LH surge (Lutenizing Hormone; initiates ovulation), continue to rise to 4-8 ng/ml on the day of ovulation (2 days after the LH surge), and may peak at levels as high as 25 ng/ml post ovulation.
After ovulation has occurred, the oocytes (eggs) must go through a maturation process before they are capable of being fertilized. This process takes approximately 2 days. When fully mature, oocytes can then be fertilized for about 48 hours. Thus, the optimum time to breed when using fresh chilled semen is 2 days after ovulation (4 days after the LH surge); and 3-4 days after ovulation (5-6 days after the LH surge) when using frozen-thawed semen due to its shorter life span.
If previous breeding history is unknown, begin progesterone testing 4-6 days after the onset of proestrus. If the levels of progesterone are baseline, then the dog should be retested every 3-4 days until a level of progesterone is detected that is consistent with the onset of the LH peek. Call the stud owner as soon as the bitch is showing signs of heat. Have your veterinarian contact the stud owner’s veterinarian after the first progesterone test is performed to begin coordination of the semen shipment. Arrangements must be made by 10:00 am CST so that semen can be collected, processed and delivered by 10:30 am the next day.
It has often been said “Timing is everything” and this is certainly true when using artificial insemination in the bitch. By planning ahead and using these guidelines, one can maximize the probability of pregnancy.