Effect of repeated horse anterior pituitary extract treatment on ovulatory response in the ewe

Twenty-five oestrus synchronised ewes were subjected to superovulation treatment with horse anterior pituitary extract, and 23 of these were similarly treated between two and six months later. Seven of these 23 ewes were treated a third time, approximately four months after the second treatment. Ovulatory response was low after the second treatment within two months, but it was satisfactory if a longer period of time was allowed to elapse. Recovery rates of eggs decreased with successive treatments, but fertilisation rates were high. Results of the present experiment demonstrate that ewes can be successfully superovulated three times within a six month period; if a period greater than two months is allowed between successive treatments, high ovulatory responses can be obtained.