Article by Olin Stephens Canine Ovulation and Progesterone Testing With most female dogs they enter their cycle every 6 months but may vary as much as 4 to 12 months between cycles. Variation can exists between the length of the "heat cycle", with the range being as short as 3 days all the way up to 3 weeks in length. The average time from the onset of heat to the actual mating period is 9 to 11 days. Making matters more confusing, some dogs have "silent heats" meaning little or no obvious signs of heat such as swelling or bleeding. Some females have whats called "split heats" where they go into a heat cycle but stop short without ovulating then go into a fertile heat period weeks later. Heat cycles can vary meaning that just because she was ready to be bred on the 11th day the last heat doesn't necessarily mean she will be ready on the 11th day of the next heat. These variations present challenges in finding the correct breeding days. The type of breeding to be performed must be considered when choosing the best days to breed. Performing natural breeding's or AI with fresh semen allow more room for error because the semen typically lives for 5 to 7 days. Fresh chilled and frozen semen the timing of the breeding is extremely important because the sperm has a much shorter life span.
The goal is to find the maximum overlap between the female's eggs which live 2 to 3 days and the male's sperm which lives less than 24 hours with frozen semen to 7 days with fresh semen. This is where progesterone testing can determine the exact day of ovulation. You can find in-house progesterone tests online but only give a range based on interpreting the fading of dots in a test kit. While in-house ovulation test kits are helpful for maximum accuracy we must use a quantitative test that measures the exact progesterone level.
Progesterone is a hormone produced by the ovaries that rises as the heat cycle progresses. Early in the heat cycle the progesterone values will usually read less than 1.0 ng/ml. The first significant rise in progesterone usually coincides with the "LH Surge". The LH stands for luteinizing hormone and is released by the pituitary gland in the brain. Ovulation occurs about 48 hours after the LH surge. The progesterone level at the time of LH surge is usually about 2-3 ng/ml. The progesterone will rise to about 5-8 ng/ml at the time of ovulation. Canine eggs are not ready to be fertilized at the time of ovulation and take about 2 days to mature. Once mature the eggs remain fertile for 2 to 3 days and then begin to deteriorate.
Progesterone stays elevated for about 2 months whether the bitch is pregnant or not. Some females will hover in the 2 to 3 range for longer the two days because of stress or just their own ovulatory pattern. It's also common for progesterone levels to vary between tests meaning today she might be at 1.5ng and the next .9ng before ovulation occurs. LH tests are helpful, but need to be run daily and can get very expensive. The "old way" of doing vaginal cytology is based on rises in estrogen not progesterone. The vaginal cytology is still helpful but not accurate enough for frozen or fresh chilled semen. Fresh chilled breeding's are usually performed 48 hours after ovulation and frozen breedings about 72 hours after ovulation. Due dates can be determined by counting forward 65 days from the LH surge (LH surge is day 0) or 63 days from ovulation. This is accurate +/- one day. Canine Ovulation and Progesterone Testing
Progesterone levels should be maintained above 2 ng/ml to support pregnancy. If a bitch is confirmed pregnant by ultrasound but cannot maintain a pregnancy, a progesterone test should be performed. Literature states that progesterone should be supplemented if it falls below 5 ng/ml. Supplementation can be performed either by a progesterone in oil injection at 2mg/kg every 72 hours, or an oral supplement (Regumate) at 0.088mg/kg (0.2cc/10 pounds daily). The oil can be measured in blood tests but the oral form cannot. Stop all supplementation 3 days prior to due date. Note that progesterone levels can drop as the result of other problems (fetal death etc) and it is often difficult to realize if the progesterone drop was the primary problem or secondary to something else. Any supplementation of progesterone should be discussed with your veterinarian and monitored closely. Hopefully this helps responsible breeders begin the process of producing healthy pups.