I have a 3 year old female Yellow Lab and a 6month old male. Recently he has been mounting her and trying to breed, but she is not in heat. Can she still become pregnant if he does succeed?!?

Yes of course she has to be in heat, the purpose of estrus is for her to be fertile. Are you sure she isn't having a silent heat? When is she due in heat? Is it close to her normal time? If she isn't in heat then she can't get pregnant. Teach him that mounting/humping is inappropriate play, that should help.

Thanks for the info! She shouldn't come into heat for about another month at least. Those few days (when I posted this question) were the only time he's done this, that I know of. So maybe it was just him, figuring out his male 'hood! I don't know! Thanks for the info anyway!

[reeskujo]

Can I ask why you haven't had her spayed yet?