I'm not sure if this is the right place to post this, but I couldn't find a place that seemed more appropriate.
I bought the property I live at last July, and the pastures were in dire shape - severely overgrown and chock full of canadian thistle and cockleburrs. I hired someone to mow the pasture down a few times this fall with the big tractors (they were armpit deep - and I'm tall) and that seems to, for now, have solves most the problem with the thistles, but the cockleburrs - oh my gosh the cockleburrs make me crazy. The amount of time I have spent this fall combing the darn things out of manes, tails, and feathers - it's a daily job and still they are a mess. Every evening is spent sitting down with tweezers to remove the cockleburr splinters from my hands. My horses are kept heavily coated with show sheen and cowboy magic to ease combing the cockleburrs out. In the spring we are spraying the pastures down with Pasture Pro and that's supposed to kill the thistles and cockleburrs, but I'm told this can be a several-years long process to completely irradicate them. The previous owners of this property just neglected everything - the house, the barn, the fences, and obviously the pastures as well and it's such a headache. Does anyone have any tips on getting rid of the cockleburrs in the pasture beyond what I am doing....or at least some good ways to keep them out of the horses?
Keep an eye on the plants and just when they're flowering, mow them down. It still takes awhile, but in the meantime you don't have to deal with the seeds spreading and creating more. 
I hate them too. I have tried burning them, herbicides and mowing. The best thing to do is make regular walks or, if your lazy like me, 4 wheeler rides around the pasture. If you see one stop and yank the bugger up. Don't drop the plant on the ground, carry it out and put it in the trash. If you pull them out of your horses mane and tail, put the burrs in the trash, don't just drop them on the ground. Wherever one of those little burrs land is where another plant will sprout. They are very hardy and can grow anywhere. I've noticed if I mow often, then the plant will just set its seeds lower to the ground. I think they have little spiky brains set on tormenting us
. After awhile you will get so you can spot a cocklebur plant from a city block away. 
that in itself would be blessed relief. We have a little over 5 acres of fenced pasture. There were "patches" of cockleburrs 100 feet wide. The previous owners of the property had horses, but the neighbors told me they just roached their horses manes and let the pasture go. It's such a shame...but I've never been afraid of a little work. It will be worth it in the end. :) 
