From The Beef Blog:
OSU researchers have used self-fed soybean hull pellets for a growing program for replacement heifers. Acidosis, bloat, and founder have all been identified as potential risks associated with feeding soybean hull pellets free choice to growing cattle. In previous research, they found that the incidence of bloat was significantly reduced and weight gain increased when cattle receiving free choice soybean hulls were fed 1.5 pounds per day of long stem prairie hay. However, this still did not completely alleviate the bloat risk.
Since cows weren’t designed by nature to eat soybean hulls, but to eat grass, it would seem to make sense to feed then a diet of 100 percent prairie hay and completely get rid of the bloat issue. But, what do I know?