| Abstract: | 183 Holstein cows were studied during and after administration of ch lormadinone acetate (CAP) postpartum. CAP was either fed orally (10mg/d ay for 15 or 20 days) or applied parenterally twice (50 mg) or once (100 mg). By oral administration, estrus was completely (=100%) and ovulation mostly (greater than 95%) suppressed, but follicle growth and estrogen production in growing follicles was not inhibited. Out of 39 closely observed animals, 89.7% ovulated after CAP withdrawal, 79.5% of them within 96 hours. With all animals inseminated, 37.5% conceived at this 1st ovulation. In 144 cows, of which 101 were orally treated with CAP and 39 by injection, shortening of the calving interval and a reduction in fertility problems was achieved. A partly significant improvement of the overall conception rate, the curtailing of the interval between parturition and conception as well as a marked reduction of the standard deviations from the mean values of those intervals were observed. Parenterally treated cows responded in a similar way. But since their 1st ovulations were spread over several weeks and since at these 1st ovulations silent heat was a considerable problem, no prediction of the timing of the 1st ovulation could be made. On the basis of the data presented on uterine contractility, ovarian functions, vestibular hyperaemia, and mucus secretion during and after CAP administration are discussed. |
