Agreed. I had to rescue back one of my horses last fall, and he came back emaciated from new holland. Once the vet cleared him from being safe fromre-feeding syndrome....he got tiny meals of soaked alfalfa pellets every few hours for a week.... He got free choice second cut hay, slowly was brought onto grass, worked up to 2lbs of alfalfa pellets twice a day, and 3lbs of a 14% protein, 6% fat grain twice a day. He gained 250+lbs in 2.5-3 months.
Growing youngsters need food. As a maintenance, they would often get 6lbs of grain a day. (14% protein/6%fat/high fiber). If they needed to gain, I would add lunch, a fat supplement, and alfalfa.