Xylose and xylan were tested in chick diets to see if they could be used as energy sources. High levels of xylose and xylan were found to be toxic to chicks. Xylan did not provide any useful energy, while xylose only gave energy at lower levels. Chicks gained weight faster when fed xylose compared to xylan, even though they ate the same amount of food. This suggests that hemicellulose, a type of carbohydrate found in plants, is not useful for feeding poultry.