please could you advise, i have a 11 month old border collie who we were not going to castrate however since this and his last visit to the vets around 7 months we have noticed that he has a retained testicle, should we get this removed asap as ihave read it can cause cancer. Also he is becomming aggresive with other male dogs to whom he normally plays with.
DEE Swindon.

The retained one will need to be removed but there is no hurry, it can wait for another 6 to 9 months, and the other can be left where it is if you wish. As to him being aggressive with other dogs it may or may not respond to his being castrated, you should try to deal with it by training. Not all dog want to play with others when they grow up but they need to learn how to leave them alone and walk on or if called return to you.