I don't send many stud requests out, but I find it's very annoying when I receive a stud request and go to accept it, only to have "This lioness needs to have a mood of 80% or more in order to breed!" come up. The annoying part isn't really getting the error itself, but the fact I have to tell the other person about it myself. So, my suggestion is pretty simple: When the stud tries to accept your request, but can't because of mood/hunger, an automated message is sent to the requester.

Another helpful feature would be if an alert was added to your rollover summary with something along the lines of "[Lioness Name] has an outgoing stud request, but has fallen below the 80% mood threshold. The stud will not be able to accept the request until her mood is raised above 80%!". That way, the requester can be made aware as soon as it becomes an issue, and can deal with it immediately, without the stud needing to attempt to accept the request for the requester to be notified.