An assessment of the value of plasma urea nitrogen and albumin concentrations as monitors of the protein status of sheep

There are two basic aspects of protein metabolism the measurement of which may assist in improving sheep management, first, the extent to which the daily requirement of the animal is met and secondly, the extent of depletion of body reserves. The need for the latter assessment arises because in some situations in which nutrient requirement and supply are not in phase it is often desirable for economic reasons to utilize the capacity of the animal to deplete and replete its body reserves. Of the major nutrients, the prediction of energy metabolism from plasma parameters has received most attention. Thus the work of Annison (1960), Reid and Hinks (1962), West and Annison (1964) relating Free Fatty Acid (FFA) concentration to rate of fat mobilization allowed the prediction not only of energy balance but also rate of energy reserve mobilisation in controlled nutritional situations (Russel, Doney and Reid, 1967; Russel and Honey, 1969; Robinson, Fraser and Bennett, 1971).