Two experiments were carried out to examine
therapeutic effect of a
gonadotropin-releasing hormone analog,
buserelin, on ovarian
follicular cysts in dairy cows.
Follicular cysts were diagnosed by palpation per rectum as well as by milk
progesterone assay. Luteinization of the
follicular cysts following treatment was judged by an increase in milk
progesterone. In Experiment 1, 35 cows were diagnosed to have
follicular cysts on the basis of palpations and low milk
progesterone concentrations 1 week before treatment. Another 19 cows which were clinically diagnosed with
follicular cysts but showed high milk
progesterone levels before treatment were excluded. Sixty-two percent (11/18) of cows with
follicular cysts treated with 20 microg of
buserelin and 82% (14/17) of cows treated with 10,000 IU of
human chorionic gonadotropin (hCG) showed luteinization of
follicular cysts within 4 to 5 days after the treatments. The percentage of cows conceiving within 100 days
after treatment and the average interval in days between treatment and conception were 44% and 42+/-18 (SD) days for the
buserelin-treated cows and 47% and 42+/-18 days for the hCG-treated cows. In Experiment 2, the effects of treatment doses (6, 10, 20 and 30 microg of
buserelin and 10,000 IU of hCG) on
follicular cysts were compared using 103 cows. An additional 23 cows which were clinically diagnosed as having
follicular cysts and which were given treatment showed a high milk
progesterone concentration on the day of treatment and were therefore excluded. Fifty to 64% of the cows responded with luteinization of
follicular cysts after treatment. There was no significant difference in response among cows given either the different dosages of
buserelin or the hCG. However, the percentage of the total number of cows that conceived after a single or a repeated treatment with 6 microg
buserelin was lower than that of cows after a single or a repeated treatment with 10 microg
buserelin (P<0.05). An increase in the dose of
buserelin from 10 to 30 microg did not improve the
therapeutic effect of the
drug. Thus, it is concluded that a single
intramuscular injection of
buserelin at a dose of 10 microg or higher is as effective as 10,000 IU hCG, and is, therefore, recommended for the treatment of ovarian
follicular cysts in cows.