GOATHEAD SOUP

I will try to be brief. I have several acres of my property that has been invaded by an evil weed they call GOATHEADS. They produce those hideous stickers that are like needles and they stick all over your shoes. When I had dogs they had the run of the place and could go ANYWHERE on my land. But the last 2 years, my property became over run with goatheads. My dogs were then confined to small specific areas. My last german shephard died in march 08 and I dont even want to get another dog until my property is free of goatheads.
HOW DID THEY ARRIVE ON MY PROPERTY?: They came into my property inside horse hay bales. That is what I found out after 2 years of wondering & investigating. My horses eat the hay, wander out into the pasture and shit the goathead seeds EVERYWEHRE they shit. Now, I have to buy my horses hay in 50 pound bags and it is extremely EXPENSIVE...but I cant take a chance on more goatheads.
SOLUTION A:.Roundup. Bought 50% roundup for about $35 a gallon. someone said that if I call the CSU extension office or the Dept. Of Agriculture, I can buy it for $25 a gallon. Is this true????...It is saturday and I dont know if they would be open...I will need a shytload of roundup and that does kill them, but that still leaves me with ground that is covered with those goathead stickers..
SOLUTION B: A girl told me today that she heard of a certain goose that will eat goatheads. Sticker and all!!!...Haha...How the hell do I contain these geese on my property? I dont know shyt about geese. Can geese be trained to stay home??? LOL
SOLUTION C: ?????????????????

those weeds really phucking suck...ANYBODY HAVE A COST EFFECTIVE SOLUTION TO THIS ISSUE? Any help is hugely appreciated. At this point I dont know whether to keep spraying or consider the GOOSE...hahaha...Oh, and I hear goats wont eat them.
What to do? thanks in advance.