Suggestion: A simple, yet noticeable (red?), banner at the top of the Stud Request Viewing page that warns you if you have any male breeding items active before studding any outside lionesses. (Any item that is given to the male which is consumed upon successful breeding- to one of your own, or to someone else's)

Even if it's just- "Male breeding items active and will be used upon next successful breeding."
A simple reminder would be VERY useful.
Here's a little mock-up example:


And if you wanted to be really fancy, the specific items could be listed below it, like-
-Buffalo Scrotum
-Great Tit
-Roasted Vulture
-Ochre Gnawrock (Male) Slot 8: Purple Polka Dots
etc, so you know exactly what's active and about to be used.
[Edit: Seeing as this also applies to people currently (May)- This should also apply to special event boosts (Tigon boost, Dorsal Fur breeding reward, etc.) I'd hate to think of people accidentally losing their special chance (and expensive items/rewards) to an accidental breeding to someone else!

I'll reiterate why this is all is an issue- other people can see when you have items/boosts active when they view your king's page for studding! While I don't necessarily think this should change, as people do sell their boosts to others- I'd like to see an extra notice on the Stud Request page for the owner of stud. I don't know about anyone else, but I generally go straight from the message link in my inbox to the Stud Requests, entirely skipping my king's page altogether! So I don't see that banner (and reminder) before breeding their lioness unless I ignore the link in the message and go to my king's page myself. /Edit]

Accidentally using an expensive breeding item on someone else's lioness without meaning to, hurts. I should have turned studding off until I had successfully used my item on my intended girl, but unfortunately I didn't think of that soon enough. I had completely forgotten I even had an item active, and focused my energy on their lioness instead. Hindsight's 20-20 and all that, but hopefully this could help prevent others from going through this in the future.

Kinda wish that it wasn't even allowed for someone to potentially (intentionally attempting or otherwise) steal your item's use that way, but I also realize it has its uses... even with its unintended side-effects.