The effects of potassium nitrate were investigated on ovarian activity, especially on ovarian activity, especially on follicle ripening and ovulation, conception rate and progesterone levels in the milk of cows with cloprostenol-induced oestrus (Oestrophan Spofa) at a rate of 500 micrograms i.m. Potassium nitrate was administered at an amount of 150 g per head/day, and this amount increased by 50 g every other fortnight to the total rate of 300 g per head/day. In a group of 11 cows exposed to potassium nitrate load, clinical examination of ovaries on day 8 after oestrus revealed the presence of CL in seven cows (63.6%), persisting follicles in two cows, and two cows did not have any CL or follicles (Tab. I). After the first insemination three cows got in calf (27.3%), and after all inseminations it was 10 cows in total (90.9%) on average in 24.4 days after cloprostenol administration, with SP 96.7 days and insemination index 1.7. No ovulation disorders were found in the control group. All five cows got in calf after the first insemination in three days after cloprostenol administration with SP 61.5 days and insemination index 1.0 (Tab. II). The progesterone levels in milk were 22.3 and 21.1 ng/ml before the second administration of cloprostenol, 2.7 and 2.1 ng/ml in oestrus and at the time of A.I., and 16.6 in eight days after insemination in cows exposed to nitrate load, and finally 21.7 ng/ml in the control group (Tab. III). Ovulation disorders were easily detectable by a clinical check of ovaries on day 8 after oestrus.(ABSTRACT TRUNCATED AT 250 WORDS)

Vysoká skola veterinární a farmaceutická Brno