What can i do to stop my jealous dog attacking other dogs?

My dog has recently starting growling and baring his teeth to some dogs, and only thing i have noticed is when i pay clap an talk to the other dog, so he must be jealous then?!?! also when i clap the local horses near my house and feed them he tries to attack them as welll, i really want to stop this before he takes it to far. any help?sorry didnt explain very well. he is 3yr old and ive had him since 9weeks old. he has just recently started to do this about 1month.i smack his bum and shout NO! he is walked in local park 3times a day so meets dogs and people every day so he is socialized, he plays with dogs and gets on great wtih them, until i pay attention to them hence i thought jealousy as he dont like me paying attention to anything apart from him.I have recently enrolled in training classes it starts on tuesday so i am doing things to solve it.

Your dog's not jealous, he's ill-behaved, not socialized, and not trained. What are you doing to correct this unacceptable behaviour? He needs to know without any doubt that it isn't going to be tolerated by you.Can't tell from your vague question whether your dog's truly aggressive or if he's an unsocialized and fearful dog. The best thing you could do for him is to get him evaluated by a qualified behaviourist and do what they tell you to correct him.

Keep him busy and do not respond to his aggression except to turn and go the other way. Next immediately enroll him in an obedience class and have him neutered right away or you will end up with a horrendously aggressive dog which you may not be able to handle.

It seems like you dont train your dog or give it enough socialization . What are you doing to correct this unacceptable behaviour? He needs to know that it isn't going to be tolerated by you.

This will help you stop the problem;http://www.dog-obedience-training-review.com/dog-to-dog-aggression.html

Cesar Millan has a website and books. He's got lots of great information. You may want to look to see if he addresses this. http://www.cesarsway.com/Calling a dog behaviorist may be a good idea. Yes, you are right, you want to stop this before it gets worse.Good luck.