Nutritive Value of Grass in Relation to Mineral Deficiencies and Imbalances in the Ruminant

Keywords: Macronutrients, Micronutrients, Herbage, Dietary requirements, Ruminants, Deficiency, Nutritional disorders, Fertility.

The importance of the inorganic macronutrient and micronutrient components of the diet are discussed in relation to the occurrence of nutritional disorders in ruminants. This paper reviews the limitations imposed on livestock productivity as a result of mineral deficiencies and imbalances in the diet and outlines recent information on dietary calcium and phosphorus requirements, for which published values have differed widely in the past. Attention is also drawn to factors influencing the risk of hypomagnesaemia and in particular the imbalance between potassium and sodium in young grass. The functional roles of the micronutrient elements in the animal are described with particular emphasis on interactions between copper, molybdenum and sulphur and copper and iron in relation to their effects on growth and fertility. Problems in assessing vitamin B₁₂ status and the adequacy of cobalt intake in cattle are also outlined.

Dr J Price, The Rowett Research Institute, Greenburn Road, Bucksburn, Aberdeen, UK.

26 pages, 5 figures, 5 tables, 105 references.