Published online by Cambridge University Press: 27 February 2018
The increasing awareness of the potential use of by-products and the recycling of waste materials, etc., presents the nutritionist with new and interesting challenges. There are several reasons for this. First, that many waste and by-products, hereafter referred to as waste suitable for animal feeding, are produced in small quantities in differing localities; often availability is very seasonal and composition varies enormously. As a result there may be some reluctance both on the part of producers and government organizations to invest a great deal in a research programme of evaluation. Secondly, the motive of industrial producers for using organic wastes for animal feeding is more often a desire to obtain a positive return by selling wastes rather than paying for their disposal, than a real interest in meeting the requirements of the animals. As a result wastes are often produced with dangerous contaminants which could have been avoided.
In many instances, therefore, nutritional advice on the use of waste in animal feeding has to be based on a knowledge of similar known feeding-stuffs and a minimum amount of analysis for basic nutritional qualities and for possible dangerous contaminants. These statements are, however, generalizations as some material, like excreta, are of variable quality and produced in vast quantities. I shall attempt to discuss briefly the nutritional attributes of different classes of waste since they are to be discussed more in detail by others at this meeting. First, a division will be made into mainly nitrogen (N) and mainly energy-yielding products and secondly the feeding systems in which they can most profitably be used will be discussed.