Cut back on the lot by the amount that is left overall. I am not yet into the science of feeding. I mix my own boost feed. I feed a bagged mixture, adding beans, oats and barley at different times. If they leave some, I cut them down. If they eat it all and are not gaining weight, I look for reasons why, sometimes giving them more, sometimes not. I was told, get the feed right to win. I don't win. I might get into the science of feeding.