Heifers eat clay So why do herbivores eat soil or chew bones? Are they just bored or are they lacking some nutrient in their diet? Many researchers don’t believe that large herbivores select foods to meet mineral requirements because research has shown that animals don’t “instinctively” recognize specific minerals. However, large herbivores can learn to prefer foods that meet nutritional needs and are low in toxins. Research supports this notion for nutrients such as energy and protein but studies on minerals have yet to be conducted.

Antelope eat soil Research assistant professor, Juan Villalba, along with graduate students, Larry Lisonbee, Chris Petersen and Tiffany Lyman recently conducted two studies at Utah State University to determine if lambs can rectify a phosphorus or calcium deficiency. In the first study, lambs learned to avoid a flavor paired with an infusion of sodium phosphate when their requirement for phosphorus was either met or in excess. Preference for the flavor paired with phosphorus improved when lambs were deficient in phosphorus. In a follow-up study, lambs deficient in calcium had a higher preference for for foods that contained calcium carbonate than lambs adequate in calcium whereas lambs deficient in phosphorus had a higher preference for foods that contained sodium phosphate compared with lambs adequate in phosphorus. The results suggest animals can self-regulate intake of these minerals and may explain why animals eat “foods” they normally wouldn't eat.

Studies with copper are planned in the future.

Previous studies concluded that animals do not have nutritional wisdom and can't balance minerals in their diets. Why did the animals in the studies described above make the correct choices? For more information read Nutritional Wisdom Revisited. or the fact sheet Mineral Nutrition: Are Animals Nutritionally Wise?