• A.T. Johns


The defining of the ideal balance of chemical compounds in the feed of ruminants, with their two-stage digestive system, is most difficult. We must consider not only the compounds as they exist in the plant itself, but also the products of their microbial fermentation in the animal's first two stomachs. A toxic substance may be detoxified or a harmless compound rendered harmful. The mineral balance may be altered in the animal and vitamins synthesised. The energy providing substances of the food are converted into an entirely different class of compounds in the rumen before being utilised by the animal. In this regard the physical state of the food may be as important as its chemical composition and the quality of the herbage may have to be defined in terms of the animal end product required