My boyfriend is often disappointed when I decide to spend time at the barn instead of spending it with him. I'll go out to the barn in the evening sometimes, and he'll call me with a sad tone when he finds out that I'm out there. He's not upset that I'm into horses, just that he gets to spend less time with me once in awhile. He has his activities that take him away from me sometimes, and it just takes communication to make sure that one of us isn't think that we'll hang out in the evening, while the other one is planning on being at the barn or doing another activity. There have been occasions when I've skipped going to the barn to spend the day with him, and there's been times that he's skipped things for me. You can't be selfish (not saying that you have been!) and feel that you are able to go out during every free moment and not have it take a toll on your relationship. However, he needs to accept that he may regularly have to do without you for a good portion of the day.
Both of you need to try to communicate when you'll be free and when you aren't. Once in awhile suggest doing something together when you would normally go to the barn. Try to get home early enough to eat dinner with him and tell him what's going on at the barn. My boyfriend is not into horses, but when I get home I'll mention a few highlights from the trip. I think it goes a long way to making him feel included, and he knows that he's always encouraged to go out there with me.
You know your husband better than I do. This could either be an adjustment period where he's trying to get used to life when you're not available every second, or this could be an indicator of bad things to come. You say that he doesn't want to go to the barn to eat lunch with you- does he expect you to come to his place of work to catch lunch occasionally? Does he get irritated if you suggest that you spend time together instead of doing his activity? Does he even HAVE a hobby that doesn't involve you? If he expects you to sacrifice your time and wishes without offering anything himself, then you have a problem. If he doesn't have his own hobbies, then that is probably part of the problem as well. If you're going to be at the barn all day, then he can't just go play baseball with his buddies (or whatever it is that men do!). Encourage him to spend that time doing something for himself, and help him to realize what that may be.
The thing that concerns me most about the situation is that he is saying that you will step on whomever to realize your dreams. That shows a lack of confidence in you as a person, and a lack of trust. It also sounds like he is trying to make you feel guilty for any steps that you've taken to realize these dreams. I don't know what you mean by getting back into the horse industry, but if you really do plan on making some sort of living out of it- training, teaching lessons, working at a barn, owning a boarding stable someday- then his actions are not promising. If he can't even handle it with you owning a horse and doing normal horse ownership things, then how will he feel if you're spending many more hours a day out there away from him working with other peoples' horses? If those are the dreams that you truly have, then he may not be the sort of person that can accompany you through those dreams.