Effect of processing on the nutritive value of cereals in animal feeds.

Since cereals provide much of the digestible energy and considerable amounts of the protein in feeds for livestock, effects of the processing to which they are subjected are of considerable practical significance. In most developed countries, a substantial proportion of the total supply of cereals is used for feeding livestock. In the United Kingdom, the Home Grown Cereals Authority have estimated that of the 22 million tons of imported and home-produced wheat, barley, oats and maize available in 1969-70, over 13 million tons were used in animal feed (Sturgess & Reeves, I 972). Unlike human foods, economic considerations are paramount and organoleptic factors are of relatively little importance in processing cereals for livestock. Processing costs can only be incurred if they are accompanied by a more than commensurate increase in the value of the cereal. I n consequence, most of the cereals used are subjected to relatively simple processes. Recently, however, there has been increasing interest in more sophisticated processing techniques, supported by the increasing economic value of cereals and animal products and the increasing size of unit in animal production enterprises. The following factors have to be considered in any study of processing (I) species of cereal and variation within the species; ( 2 ) the particular process or processes applied; ( 3 ) species and class of animal fed; (4) relative place of the cereal processed with respect to the rest of the diet of the animal. Apart from the problems posed by the variation in the reaction of theanimal, which is often not sufficiently well-defined to allow clearcut definitions of requirements for processing, there can be appreciable differences in the physico-chemical properties within each species of cereal grain, which can interact with the process. Furthermore, the processes are often poorly controlled and their effects upon the physical and chemical properties of the grain are not completely understood. It is therefore not surprising that there is often considerable contradiction in the results relating to the application of a particular process to a particular cereal fed to a given category of animal. Four processes are considered in this paper.