INGESTEnD SOIL AND ANIMAL NUTRITION

SOILS are usually considered to influence animal nutrition through the quantity and quality of the herbage they produce, so that the sequence is soil-plant-animal. The fact that soil is ingested by grazing animals indicates that a direct soil-animal effect also needs to be considered. Soil is taken in by animals along with herbage, as soil adhering to leaves, as soil on roots, and as earthworm casts. Grazing of root crops to ground level or below is another source. The bulk of the ingested soil is probably taken in accidentally along with herbage and is a consequence of intensive management. Soil ingested because of depraved appetite is probably of rare occurrence. Under New Zealand conditions with animals wintered outdoors, sheep can ingest up to about 75 kg of soil annually, and dairy animals up to about 600 kg. While these are large amounts of soil, they are less than perhaps 2% of annual fresh matter intakes. However, because elements may be present in soil at much higher concentrations than found in pasture, this soil may have important nutritianal effects.