Correlation of periovulatory serum and fecal progestins in the domestic dog.

This study was initiated to determine the relationship between canine ovarian steroids detected in serum and feces during the periovulatory interval in domestic dogs, and to examine the feasibility of a non-invasive method to estimate the time of ovulation in canid species. When bitches (n = 14) were observed to enter proestrus (based on vulvar enlargement or serosanguineous vaginal discharge), paired daily serum and fecal samples were collected for a 15- to 20-day period and stored at -20 degrees C. After extraction, progestin concentrations in both substrates were measured using an established enzyme immunoassay procedure. All samples were aligned to Day 0, the first day in which fecal progestins reached a sustained rise above 100 ng/g feces. Mean fecal progestin concentrations increased in parallel with mean serum progesterone values (r = 0.78), rising from 44.6+/-2.6 ng/g feces to 409.6+/-90.9 ng/g feces, and 5.4+/-0.9 nmol/L to 81.2+/-18.5 nmol/L, on Day -5 and Day 5, respectively. Individual fecal progestin concentrations varied markedly, but plotted against serum progesterone concentrations demonstrated correlation coefficients ranging from 0.41 to 0.97 (P<0.05). These results demonstrate that sequential changes in domestic dog serum ovarian steroid concentrations are paralleled in the feces, and that it is feasible to non-invasively monitor individual progestin changes in the periovulatory interval using fecal hormone analysis.