Antinutrtiional means yes, it can inhibit the absorption of certain nutrients or otherwise cause digestive problems. Honestly, that's true of everything, to greater or lesser degree.
The biggest always problem with barley is the presence of beta-glucans. Oafter oats, i think barley have the...
Yes they can. Barley is high in certain antinutritional factors, for which you should either treat, compensate, or keep quantities small as a percentage of total feed.