From the article it looks like they were left in for one season. That would give you a year's freedom though from shots and/or implants. My neighbor could have really used this information a few years ago. He finally sold his riding mare because nothing seemed to work.
Heh... I'm now waiting to see if all heat cycles go like the last one, or if they settle down. It is interesting!
Well I'm glad I didn't have Sarah Lee bred this year. I really thought about it but common sense won out:')