I build all mine from scrap pipe I picked up from scrap yard. Do you plan on feeding square bales or round bales? How many cattle? Do they have horns or no horns? What I have found works better than feeders, is you take the round bales out onto the pasture at the start of the feeding cycle. Line them up in rows 15 feet apart with enough hay in each row to last one week, per month of the feeding season. Start feeding from the end of the row which is nearest the source of water. Only use sisal twine or remove the twine each week with a knife. Between the row of bales were you will start feeding and the next row for next week run an electric wire. When they have finished the first row move the wire back one bale. This works well because you fertilize your field, you put all your winetrs hay out at once in good weather. You never have to clean the manure from your yard or stables. It saves alot of work fuel and wear and tear on machinery. Try it you will like it a lot.
Sisal twine is made from a plant. It was the original organic binder twine. If the cow happened to eat it she would just digest it. If it was left in the yard or field it just decomposed like any other plant. I would'nt have any other.