Hi Seven, welcome to TBN, hope it's a long stay. (Warning: it's highly addictive, and can lead to actual tractor use LOL)
As far as me being an "expert on trees and brush" - I can kick tree butt with the best of them, but brush and mesquite (never actually seen one, but I've heard 'em buzzing around) aren't my strong suits. I've never even run a bush hog, ever - just read a lot about 'em. So you've found me out - I'm not a tractor expert, I just play one on the internet. /forums/images/graemlins/laugh.gif
If you give some more details about exactly how the brush grows near the fences, do you have to get both sides of the fence, height/type/other dimensions of the fence, terrain, etc., that might help us figure out what might be best. It might turn out that there's a type of
grapple I'm familiar with that might do some good, or someone might suggest something else like a flail mower, bush hog, sickle bar, who knows. There are things called right-of-way mowers (ROW) that kick butt on brush and small trees. I've seen them mostly for good-sized Bobcats and larger wheeled and tracked vehicles. They get pretty heavy and usually require quite a bit of power to run the hydraulics, so they're not for CUTs, or maybe anything less than an M9000 or bigger. Also, I've seen some good recent threads on tree shears for (CUT and up) tractors - maybe do a search for "Tree Eliminator". Dymax is one of the more popular "big brothers" to the T.E. among land-clearers.
Ditto on the mesquite as far as additional info - height, diameters, how thick is it growing, terrain, what you're going to do with it after you cut it (burn it?).
Also, someone might suggest a chemical approach to the brush along the fence. Roundup is pretty benign, and has the advantage of killing stuff dead so you don't have to keep cutting it. You can get it for as little as $1/gallon (after dilution) at Home Cheapo, probably more like $.60/gallon in 55-gallon drums. Might cost you several thousand dollars per application for seven miles of fence, but it might be worth it since it won't grow back (as much). Hook up a tank sprayer and go to town maybe, just like they do on the highways. Kill it and then whack it with something, or let mother nature take care of the rest (like Exxon did in Prince William Sound /forums/images/graemlins/smile.gif /forums/images/graemlins/shocked.gif
Anyway, hope this helps somewhat, and again, welcome!
John D.