Maybe there is, and maybe there isn't. Did your boy get to your bitch?
Some boys have no change and are just as goofy and loving and sweet after they have achieved the wind and rain, and others note a change in the dog after having bred a bitch.
The act of breeding is not like lady and the tramp, when the bitch is ready, she is usually, but not always willing to stand for the male. When she is not ready, she will not stand. But a dog that has to chase a bitch down to complete the process, may have to be a little aggressive himself. I don't mean biting or hurting her. But she might be aggressive to him, and he will have to be able to take her crap, and still chase her down and dominate her.
If the breeding was orgestrated -- the bitch is muzzled and/or held in place while the dog does what he needs to do, until a tie happens. Then usually the muzzle can be removed and everyone waits for the tie to release, without the bitch becoming hysterical and dragging him around, etc. Well in this case the dog does not need to exhert a more aggressive nature. And I haven't seen a dog change for the worst after this type of breeding.
I have heard of a young male attacking a small girl who had been playing with a female who was in heat earlier in the day. This was years ago and a king shepherd, but it is hormones. Sometimes a dog will become full of himself after breeding a female, and he needs to be brought back to reality and quickly.
Jenna, RN CGC & Babs, CD RA CGC HIC
Heidi, RA CGC
SG3 Odessa, SchH1, Kkl1, AD
Ninja, RN CGC & Milla, RN CGC
Joy, Star Puppy, RN CGC
Dolly CGC & Bear CGC