My 5 month old rooster keeps attacking my dog

[Aw4842]

What changed is his age, and the hormones that come with it. There's no reasoning with it , there's no changing it and there's no fixing it. It just is what it is. Some cockerels become very protective of "their" females, like your boy keeping that pullet away from you. That's not likely to change except possibly to get worse. If this cockerel is flying at young children or flogging them, he needs to be removed. He can do serious harm to a child, psychologically as well as physically.

I would never let harm come to anyone. If I see he doesn't get thru this phase, I will rehome him. Thanks