Factors affecting the voluntary intake of food by cows

In farming practice it is often difficult to get animals to eat the amounts of the lowpriced roughages which are desirable economically.Satisfactory levels of animal production can then be achieved only by the use of higher-priced foods.It is important, therefore, to understand the factors that control the voluntary intake of roughages.The probable importance of the filling effect of roughages in the reticulo-rumen has often been stressed (cf.Makela, 1956; Crampton, 1957), but apart from a few brief remarks by Schalk & Amadon (1928) there appears to be little direct experimental evidence for this probable effect.The experiments described here were carried out as a preliminary to the more detailed studies which will be discussed in later papers of this series.This paper deals with the effect, on the voluntary intake of food, of various increases or decreases in the contents of the reticulo-rumen.We wished to know whether changes in the amount of the reticulo-ruminal contents had a direct effect on the voluntary intake of hay.It appeared necessary to investigate: ( I ) the importance of the amount of digesta in the reticulo-rumen at different times relative to the offer of food, and ( 2 ) whether any effects observed were due to the amount of the contents per se or to the nature of the materials forming the contents.