The important thing for pigs is lysine. Without sufficient lysine, they do not grow well. Dairy provides lysine, which is why people will take whey from cheese operations to feed out. Eggs are another source but should be cooked before feeding, to double the available protein.

Pumpkins, apples, beets, turnips, kale, rape, sunflowers, sunchokes are all good to feed. One can feed hay or pasture, but a lysine source must be provided.

Regarding mowed grass, it must be dried in the sun, and turned often while drying. You'd have less work scything it. It would dry and store better.

And if the food you are buying by the half ton is broken grain, that seller is trying to make a sale, not provide nutrition....no wonder it's cheap. One gets what one pays for... remember GIGO.... You want good food and healthy pigs, it's not cheap.