Donkeys obtain most of their energy from structural carbohydrates. Some suggest that a donkey needs to be fed only straw (preferably barley straw), supplemented with controlled grazing in the summer or hay in the winter, to get all the energy, protein, fat and vitamins it requires; others recommend some grain to be fed, particularly to working animals, and others advise against feeding straw. They do best when allowed to consume small amounts of food over long periods. They can meet their nutritional needs on 6 to 7 hours of grazing per day on average dryland pasture that is not stressed by drought. If they are worked long hours or do not have access to pasture, they require hay or a similar dried forage, with no more than a 1:4 ratio of legumes to grass. They also require salt and mineral supplements, and access to clean, fresh water. In temperate climates the forage available is often too abundant and too rich; over-feeding may cause weight gain and obesity, and lead to metabolic disorders such as founder (laminitis) and hyperlipaemia, or to gastric ulcers.