Aggressive dog problem and bitch in season

[FruitAndFivers]

Our normally docile collie has turned quite aggressive (he bit me and went for a visitor) and I am not sure how to reassure him and get his trust.

Our other collie, a 10 month female has just come into season and I wonder if he is being very protective with her.I was bitten when I was fussing over my girl, same as the visitor.

He has recently been castrated (two months ago) and we had hoped to get our girl dressed but the castration cost £200 and we could not afford both operations at once.

Will the vet neuter a bitch in season or is there something they can do/give her to stop being in season?
Is this what is upsetting our boy?

I'm quite wary of him now and he knows it. How can I overcome this and trust him again? He is a working dog and we used to have a brilliant working relationship, great trust best friend.
He seems to now favour my partner.

Will he become less aggressive when our girl is not in heat?

The vet won't spay a bitch in season. It would have been better to have the female neutered if you could only afford to have one dog done. Your boy dog will be attracted to the bitch. He can and will mate fully with her and might still be capable of getting her pregnant. You need to totally separate them for the whole of her season, after which he will probably return to normality.

Thanks outmonday.

I spoke to the vet today and bitch is pencilled in to be spayed in a few weeks time.
Dogs have been separated, male is now with my family until things return to normality. Bitch is coming to the end of heat in a few days if it lasts for 3 weeks or so.