I don't know at all if the mare's attitude is what shows it but we're almost always right on having colts or fillies, when we breed them. I knew I was having 2 colts last round, had the names Baryshnikov and Nureyev picked out without backups because they'd be stunning colts, and they were. But I don't think it's the mare's behavior that tells me. I cannot even guess what it is.
Now... here's something to check back on. We're planning to breed our 2 warmblood mares in 2025. The big mare we're breeding to an Arab stud, same combination we'd done for Nureyev. The smaller one is standing to our own stallion. We have not bred her before. We're expecting 2 fillies out of them. Let's see if we're right!