This is a little bit different from exactly what you asked but assuming this is for deer recovery then I know a chap who recovered the occasional red deer and who managed to buy up a job lot of decent rope from British Telecom who were selling it in something like 500 yard lengths. It wasn't super amazingly strong, but he found it was strong enough to drag out a red deer. He got himself some sort of block and tackle arrangement with a very high mechanical advantage and ran out the rope to the deer. He said that it was important to get as much of it off the ground as possible and so would secure his gear as high up a tree as he could reach. Now it all sounds a bit of a faff to me but on the other hand if you have a dead deer that you can't move at all then it is progress. He said that he just threw the rope away once it was used, he bought quite a few drums of it and only shot the occasional red.
I know it is a pretty strange approach, with lots of serious limitations, but maybe it will give you some ideas.