I agree, even if you had the dog castrated, he may well still be interested in the *** when she is in season, as will all the dogs in the neighbourhood. Apart from pyometra, there is also the risk of mammary tumours in unspayed ***. There is a slight risk to uncastrated males from prostate cancer, but it is very slight and unless he is a 'wanderer' I would not bother to have him done.