Animal Industry Report

Extension Number

ASL R2535



Summary and Implications

The objective of this study was to test the effectiveness of Cystorelin™ (gonadorelin diacetate tetrahydrate) in inducing ovulation in cyclic mares. Mares were treated with either three 75 μg (1.5 mL) i.m. injections of Cystorelin™ or three 1.5 mL i.m. injections of sterile saline (control) given two hours apart. Blood samples were collected every 30 minutes to monitor LH concentrations. No difference was observed in LH secretion patterns of control and treated mares. Mares treated with Cystorelin™ ovulated 2.25 ± .25 days after treatment which was one day earlier (P<.05) than control mares (3.25 ± .41 days). Of the treatment mares, 71% (12/17) ovulated within 48 hours after treatment compared with 14% (1/7) of control mares. Treatment and control mares were not different (P>.81), however, for variability in days to ovulation. Treatment with Cystorelin™ effectively hastened ovulation in mares, which could prove useful for timed artificial insemination. Further research is necessary, however, to develop a protocol that can also reduce variability in the time of ovulation.

Copyright Holder

Iowa State University