When you say 'seasoning' I assume you mean winking and squirting at strange horses, particularly geldings. Yep - lots of in-foal mares do it! My first year breeding I put 3 in-foal mares in the field behind the stallion paddock. Turned him out and within 2 minutes, all 3 were lined up along the fence winking and squirting furiously. He said: "Hi Ladies, see you next year" and returned to grazing! I breathed a sigh of relief!