Milk and Serum Progesterone Levels in Mares after Ovulation

Twenty-four Finnhorse mares were examined by rectal palpation and ultrasonography every 6 h during late oestrus to determine the time of ovulation. Milk and serum samples were collected every 6 h after the detected ovulation for progesterone analysis. The progesterone rises took place within 0–54 h and 0–60 h after ovulation, in milk and serum, respectively. Statistically significant differences (p < 0.05) in progesterone levels were observed for the first time 12–18 h and 18–24 h after ovulation, in serum and milk, respectively, as compared to progesterone levels 0–6 h after ovulation.