Change of dog behavior

Question
Hi, I have a Bull Mastiff who is just over 2 years old.  He is quiet, well behaved, obedient and never aggressive.  We bought a kitten 10 days ago and after a jumpy first couple of days the two of them seem to be getting on really well - they leave each other alone and sleep in the same room together with no trouble at all.  There has been a couple of changes in the Mastiff's behavior since though, he has become very whiny - I don't know if we have been spoiling him or not.  He whimpers to go out for a walk even though he's just back from an hour long walk in the woods, and won't eat his food until he's starving because he thinks he'll get some of ours - he sits begging whenever we are eating.  Tonight was the final straw though, I was out walking him up the woods and we came across another dog, just a small old dog, but Tyson, my dog, attacked her.  I had him on his leash and had to pull him off.  The other dog was hurt, but not badly.  Why do you think he's behaving like this?

Answer
Hard to say exactly what happened on the walk. He's getting close to social maturity now, and dog aggression isn't unheard of in mastiffs. Or if it was a very small dog, he may have seen her as prey. Or she may have gotten in his face and he found that rude. Or he didn't want the dog close to you. Many reasons why that may have happened, and on the information given, I can't pick out one as THE reason.
The other stuff really does sound like he is spoiled though. If he gets whiny, give him something else to do. Maybe some puppy push-ups (sit/down/sit/down) and do NOT reward him for whining by giving him what he wants. That only reinforces the whining.
As to food, why would he want kibble if he can have pot roast instead? Unless there is a physical issue, picky eaters are generally created by owners trying too hard to please their dogs. A healthy dog won't starve himself, and this is the best article I've seen on getting your dog over being picky about food.
http://dragonflyllama.com/%20DOGS/Writing/TeachEat.html
Print it out and put it on your refrigerator. Of course, this is NOT something I would do with a dog who resource guards food or objects from humans. If that is the case, or if he starts getting grumpy about you taking his food, I would hand-feed, placing two or three kibbles in his dish, ask for a sit, and place a few more kibbles. I would also use his food for training.
My guess is this dog pretty much gets to do what he wants, and the people in the house let him, or help him. That's not good with any dog, certainly not with a dog the size of this guy. I would be getting some obedience training on him, and asking him to do something for me for everything he wants in life. Want your dinner? Wait at the kitchen door while I fix it. Don't want to wait? Fine, the dish goes up and I leave the room. Come back in about 30 seconds and we start over. Want to go for a walk? You have to sit and be quiet while we get the leash. Can't do that? Fine, I'll sit down and read for a bit. In this way, you are teaching the dog that you are the leader and the maker of rules. He needs clear-cut guidelines and consistency. Dogs who don't have that tend to try to make the decisions about what happens, and dogs just aren't very good at doing that in a human-run world. And they are much happier in the long run if they know they don't have to. Sandy Case MEd CPDT www.positivelycanine.com