Progesterone concentration in milk and blood serum and reproductive efficiency of cows after Ovsynch treatment

An experiment was conducted to investigate the effects of hormonal synchronization of ovulation on progesterone concentrations in milk and blood serum and on reproductive performance. Sixty Holstein-Friesian cows averaging 8000 L over 305 days of lactation were divided into 2 groups of 30 animals. One-factor ANOVA and a t-test of progesterone concentrations in venous serum and milk revealed that the lowest concentrations of progesterone in milk (Ovsynch 5.8 + 1.0 ng/mL; control 4.5 + 0.6 ng/mL) and blood serum (Ovsynch 1.3 +/- 0.9 ng/mL; control 1.4 +/- 0.5 ng/mL) in both groups were found on the day of estrus or artificial insemination (AI) (both P < 0.05). Increases in the concentrations of progesterone in milk (Ovsynch 17.6 +/- 4.3 ng/mL; control 10.5 +/- 1.9 ng/mL) and blood serum (Ovsynch 3.6 +/- 1.1 ng/mL; control 4.0 +/- 1.0 ng/mL) were observed on day 7 after AI (both P < 0.05). Concentrations of progesterone in milk and blood serum in nonpregnant cows were reduced on day 21 after AI. Assessment of reproductive performance revealed that the application of treatment shortened the duration of the service period (Ovsynch 76 days; control 83 days) and the calving interval (Ovsynch 376 days; control 382 days)