hello everybody,
I am just wondering if someone can help me! I have a 4 year old shihtzu called fudge.
He used to love other dogs even when they barked or growled at him he would still be happily sniffing them and whatsoever.
However all of a sudden he hates other dogs! If one is in sight he will pull like mad on his lead and as we get closer he will bark aggressively and snap (I'm not sure of this is a warning)
He has never had a bad experience to make him turn this way. We have a bitch who is 10 months old and it took him a little while to get used to her as a pup and he was castrated a couple of months ago. I'm so confused, I don't know why he is behaving like this?! Has anyone had similar experiences with there dog? Anyone have any idea how we can resolve/help this? we are going away for 5 nights in september and he will be staying with someone locally who has two dogs himself, however he said he will happily take him on and see how he goes but im just so nervous! but i am scarred from the last kennels they went in so never again are they going in a kennel!
Help would be much appreciated. Thanks. :)

Character never changes suddenly in the adult dog without reason so the first step would be to have a full health checkout. If the vet and blood tests show nothing amiss then you will have to think the change is because of the recent castration and that he is feeling vulnerable and is in fact very insecure, there is not much you can do except perhaps use a form of HRT and give him male hormones. Or it may be simply that the new pup has put his nose out of joint but that would be unusual it would I suppose depend on how much attention and petting he got before.