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The following article is reprinted from the website of The Canine Semen Bank of Columbus with the permission of Dr. Mark McCloskey and Dr. Erik Weisgerber.
Most female dogs cycle twice a year with lives for 5 to 7 days. However, with fresh an average interval being 5 to 11 months chilled and frozen semen the timing of the between cycles. Breed variations do exist, breeding is much more critical- because dog breeds such as the Basenji, that only cycle once a year. Variation also exists between the length of the “heat cycle”, 2 to 3 days) and the male’s sperm (lives all the way up to 3 weeks in length! The heat (proestrus) to the actual mating period determining an exact ovulation date (estrus) is 9 to 11 days. To make matters more confusing, some dogs have “silent heats” meaning little or no obvious signs of range based on interpreting the fading heat such as swelling or bleeding are ever of dots in a test kit. While these are heats” exists where dogs go into a heat quantitative test- meaning it measures the cycle but stop short without ovulating then exact progesterone level and gives us a go into a fertile heat period weeks later. A number. female’s fertile period can be different from heat cycle to heat cycle. Meaning that just Basically, progesterone is a hormone 11th day the last heat doesn’t necessarily mean she will be “ready” on the 11th day usually read less than 1.0 ng/ml. The first significant, sustained rise in progesterone usually coincides with the “LH Surge”. The is released by the pituitary gland in the breeding (type of semen) to be performed brain. This is important because ovulation occurs about 48 hours after the LH surge. The progesterone value at the time of the LH surge is usually about 2-3 ng/ml. The progesterone will rise to about 5-8 ng/ml PAGE 46 * THE WEIMARANER MAGAZINE * SEPTEMBER 2008 at the time of ovulation. Canine eggs are Progesterone levels should be maintained not ready to be fertilized at the time of above 2 ng/ml to support pregnancy. If a ovulation and take about 2 days to mature. bitch is confirmed pregnant by ultrasound Once mature, the eggs remain fertile for 2 but cannot maintain a pregnancy, a to 3 days and then begin to deteriorate. At progesterone test should be performed. the time of insemination, the progesterone Literature states that progesterone should can be in the teens and into the 20’s (ng/ be supplemented if it falls below 5 ng/ml. ml). Progesterone stays elevated for about Supplementation can be performed either by a progesterone in oil injection at 2mg/kg progesterone is helpful between day 3 and (Regumate) at 0.088mg/kg (0.2cc/10 pounds daily). The oil can be measured in cytology shows about 50% cornified cells. blood tests but the oral form cannot. Stop After interpreting the baseline number, we all supplementation 3 days prior to due then test every 48 hours to best pinpoint drop as the result of other problems (fetal ovulation. Some females will “hover” death etc) and it is often difficult to realize if the progesterone drop was the primary days because of stress or just their own ovulatory pattern. It is important to see the Any supplementation of progesterone progesterone level peak “5” ng/ml to feel should be discussed with your veterinarian luteal insufficiency in a bitch. J Am Vet Med LH tests are helpful, but need to be run daily and can get very expensive. The “old way” of doing vaginal cytology is based LH surge- usually around “5-8” ng/ml The vaginal cytology is still helpful but not • accurate enough for frozen or fresh chilled • surge is day 0) or 63 days from ovulation. performed if the progesterone is less than SEPTEMBER 2008 * THE WEIMARANER MAGAZINE * PAGE 47

Source: http://weims.ca/downloads/Breeders%20Briefcase/BECColumn-Progesterone.pdf