Effects of
PGF2(alpha) analog (ONO-1052) on cows with luteinized
cysts following treatment with
GnRH analog (
fertirelin) in inducing estrus and shortening an interval from treatment to conception were investigated in a field trial. Seventy-five cows with
follicular cysts diagnosed by rectal palpation were treated intramuscularly (i.m.) with 400 mug
fertirelin (an analog of
GnRH). Luteinization of
follicular cysts were tentatively judged by rectal palpation. Forty-one cows were considered to have luteinized
cysts and were either treated i.m. with
ONO-1052 (28 cows) or left untreated as controls (13 cows). Thirty-four other cows were considered to have not responded to
fertirelin and retreated with 10,000 MU hCG (19 cows) or
fertirelin (five cows). This tentative judgment of luteinization of the
cysts by rectal palpation
after treatment was later confirmed by determining serum
progesterone concentration before and 10 to 14 days
after treatment. Only in the cows with luteinized
cysts which were confirmed by serum
progesterone analysis; increased from a pretreatment level below 1.0 ng/ml to a value of 1.0 ng/ml or higher 10 to 14 days
after treatment, effects of
ONO-1052 combined with
fertirelin were investigated. Of the 18 cows with luteinized
cysts thus confirmed following
fertirelin injection and treated with
ONO-1052, 15 (83.3 %) cows came into estrus within 26 +/- 14 (mean +/- SD) days after the first treatment; eight cows within three to five days and four cows within 22 to 28 days, and 14 cows (77.8 %) conceived within 100 days (42 +/- 26 days). On the other hand, the five control cows with luteinized
cysts that were not treated with
ONO-1052 required significantly longer to exhibit normal estrus (54 +/- 13 days; P<0.05) and to conceive (54 +/- 13 days). These results indicate that
ONO-1052 combined with
fertirelin may be useful to shorten the interval from treatment to normal estrus and to conception in cows with
follicular cysts.