Can male cows be entered into contest?

[faarmer]

My male cow is an adult but I can't enter it in the contest. It keeps saying it's not matured.

It doesn't have full hearts yet- can you only enter cows with full hearts?

[Cherubae]

You can enter a cow with less than 10 hearts and still earn a little bit of farm popularity. I don't see anything in my resources that indicates only female cows can be entered into the farm union contest, so it may truly not be an adult yet. Try a different cow or try one of your female cows and see if that works.