It might be cheaper to make it at home, but you'd need to have it tested every now and then to make sure it's got the correct nutrients and minerals. I think it's easier to supplement their commercial food with forage and kitchen scraps, rather than taking on their whole diet. I'd worry about getting it right.
Commercially made feed is more convenient to use and it's easier to disperse. I could see myself feeding cows and pigs without using commercial food, but I’m not sure that I could get away with it with fowl.
I think it depends on the number of livestock on the farm, the kind of feed they consume, and whether the farmer has the know-how. I would opt for the commercial and not home-made option if this allowed me to devote more attention to the livestock.