Robust Luteolysis of Corpus Luteum in Cyclic Ewes with Castor Beans

Objective: To study a probable luteolytic effect of castor beans in ewes and find which part of the bean is effective.

Methods: in experiment I the estrous cycle of 30 desert ewes was synchronized with 2 im injections of 125 μg PGF2 α, 9 days apart. Then the ewes were grouped into 3 groups: A, B and C (10 ewes each). Each ewe in group A was fed 2-4 gm of whole castor beans on day 9 of the estrous cycle (T1) and each ewe in group B was fed 6-8 gm (T2). Group C was left to cycle naturally to serve as a control. Experiment II investigated the effective portion of castor beans. The testae (outer shells) of 8 gm castor beans were removed and separated from the decorticated part. Then 10 cyclic ewes were divided into 2 groups. Group I (n=5) were fed the decorticated castor beans and group II (n=5) were fed the castor beans’ testae.

Results: A significant (p<0.001) number of the treated ewes in experiment I expressed estrus 3 days after the treatment and their serum progesterone levels dropped down significantly (p<0.001) on day 12 (0.63 ± 0.07 ng/ml) compared to that of the control (2.63 ± 0.04 ng/ml). In experiment II 72 hr after treatment 3 out of the 5 ewes treated with castor beans’ testae expressed estrus and their mean serum progesterone level was 0.06 ± 0.01ng/ml; while the ewes treated with the decorticated beans did not show any signs of estrus.

Conclusion: Castor beans are luteolytic in ewes and the probable luteolytic substance is present in the testae. Thus castor beans and/or their testae can be used as contraceptives, abortifacients or as estrus synchronizing agents.