If a food source has an identifiable flavor, an animal can learn to associate the positive effects of alleviation of a certain nutrient deficiency with consumption of that food. This has been demonstrated in a variety of species: lambs offered free choice of various foods will compensate for phosphorus, sodium, and calcium deficiencies. Domestic fowl have demonstrated specific appetites for calcium, zinc, and phosphorus, thiamine, protein in general, and methionine and lysine. Heat-stressed fowls seek out vitamin C, which alleviates the consequences of heat stress Learned specific appetites are not necessarily a result of an animal's ability to detect the presence of a nutrient. Because nutrient deficiencies of various types can have stressful effects which vary depending on the missing nutrient, subsequent ingestion of that nutrient is associated with relief of certain signs. An animal may therefore associate the flavor of a food that is high in a certain nutrient with relief of the signs of that nutrient deficiency, while not seeking out other foods rich in the same nutrient.
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