Yeah, my oldest son is about the same age and hates everything about animals, tractors, and being outside. Says he wishes he lived in town instead of on a farm.
I've done all I can think of to try to get him interested, but people like what they like, I guess. Maybe he'll come around, maybe he won't, but there's no sense in trying to force what I like on my kids I figure.
Luckily, I've got two younger ones coming up who seem to love the farm (for now!). His baby sister in particular loves tractors and cattle. I don't remember that attitude from either of her brothers at any age. Maybe loving tractors is just something you're born with (or without) :)