13. The Role of Pasture in the Mineral Nutrition of Farm Animals 1

The adequate mineral nutrition of farm animals depends upon a number of inter-related factors. In the first place, there must be a sufficient supply of those minerals required for the normal functioning of the body processes. In the second place, efficient mineral nutrition depends upon the existence of a proper ratio between certain elements, for example calcium and phosphorus. Then there is the assimilation factor, usually referred to as vitamin D, which makes for a more efficient assimilation of calcium and phosphorus. Finally, there is the question of the harmful effect of certain elements when present in excessive amounts in the ration. With all of these factors pasture is concerned, and the question of mineral nutrition on pasture is of major importance in viewof the fact that over long periods pasture grass is the sole feed, particularly for certain species, in contrast to the conditions found in dry lot or in stable feeding where the ration consists of several feeds and where a deficiency of a certain element in one feed may be balanced by an excess in another. In view of this fact it is not surprising to note that the lack of adequate mineral nutrition first came to the attention of stockmen through observations on pasture and that the most extreme cases of malnutrition and disease which have been recorded as due to mineral deficiencies are those which have been observed on pasture.