Barley is commonly used in Canada and Europe as the major energy source in poultry diets but is considered a low-energy grain. The lower energy value of barley is due to low starch content, a high fiber content, and the presence of beta-glucans. Beta-glucans cause low digestibility and sticky droppings.  The sticky droppings create bad litter, which can cause hock problems and damage the breast of broilers.  With layers, the sticky droppings adhere to the cage and mark eggs decreasing their quality and marketability.  Barley is considered inferior to either corn or wheat as an ingredient in poultry diets. Barley contains twice as many fatty acids as wheat, which accounts for its 10% higher caloric content. Barley contains over 17% fiber, which is 40% more than that wheat.

Poultry fed diets based on barley have been shown to be more susceptible to necrotic enteritis than those on corn-based diets. The development of commercially available enzyme preparations has increased the use of barley in poultry feeds, but the use of feed enzymes is restricted in certified organic poultry production.

Sticky droppings: A feed-related poultry problem (Washington State University)

Barley-grain - Feedipedia

The Saskatchewan encyclopedia - barley