ABSTRACT
Nine "animal factors" influencing the relationship between trace element status in soils, pastures and grazing animals create difficulties in predicting growth-limiting deficiencies in lambs from soil or herbage composition. Many factors will determine whether or not a soil of particular trace element composition will give rise to deficiency (or toxicity) problems in grazing animals. The inadvertent ingestion of soil as a pasture contaminant may influence the trace element status of the grazing animal in either positive or negative ways and must therefore be considered in models for the prediction of risk of trace element deficiency. Growth retardation at two improved hill sites was preceded by heavy losses due to miscellaneous infections. The complete model for the factors which determine trace element status of grazing sheep is so complex that it seems unlikely that trace- element responsive conditions will be predictable on a farm-to-farm basis from analyses of single or multiple constituents in soil.
