Lack of LH response to oestradiol treatment in cows with cystic ovarian disease and effect of progesterone treatment or manual rupture.

The luteinising hormone (LH) surge in response to 1 mg oestradiol benzoate intramuscular injection was studied on 67 occasions in 45 cows with cystic ovarian disease 20 to 150 days post partum. Cows diagnosed as having luteal cysts were given 500 micrograms cloprostenol intramuscularly 24 hours before oestradiol, to induce luteolysis. Oestradiol benzoate was also given to eight post partum acyclic and eight cyclic cows and in all these cases a control LH response was characterised for comparison. Eight of 17 cows with luteal cysts (47 per cent), and 10 of 21 cows with follicular cysts (48 per cent), released LH in response to oestradiol. Some cows with cysts were given one of two treatments. Seven cows with follicular cysts were treated with a progesterone-releasing device (PRID) for seven days: all responded to a second oestradiol treatment given 24 hours after removal of the PRID. Luteal cysts in three cows and follicular cysts in nine cows were ruptured manually: only one cow (a luteal case) responded to the second oestradiol treatment given 24 hours after manual rupture. In eight cows initially diagnosed with luteal cysts, cloprostenol was not given and plasma progesterone concentration at the time of oestradiol treatment was high (over 0.9 ng ml-1): none released LH in response to oestradiol. As manual rupture did not improve the LH response to oestradiol, it is concluded that the defective LH response to oestradiol in cows with cystic ovarian disease was not influenced in the short-term by cyst fluid contents.(ABSTRACT TRUNCATED AT 250 WORDS)