A High Roughage System for Raising Calves Based on the Early Development of Rumen Function. I. Effect of Variations in the Ration on Growth, Feed Consumption, and Utilization

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Abstract
Economy in feeding the ruminant is based fundamentally on taking full advantage of rumen function, with particular emphasis on the digestion of roughages and the synthesis of high quality proteins and vitamins. In efforts to apply this axiom to calf feeding, preliminary work indicated that mature type rumen function could be established in young calves much earlier than was generally thought feasible (9, 10). Young calves receiving only limited quantities of milk were raised satisfactorily on a high-roughage, low-cost ration similar to that usually provided older cattle. The ration consisted of approximately two parts good quality mixed legume-grass hay and one part of a simple 14.5 per cent total protein grain concentrate mixture. In the preliminary experiments considerable attention was given to management factors which were observed to influence the health and the early development of rumen function of young calves, including rumen inoculations (11, 12, 13). The purpose of the following experiments was to study some variations which could be made in this basic high-roughage feeding system in order to obtain maximum efficiency of feed utilization and low cost along with normal growth and health. A simple grain concentrate mixture was compared with a complex calf starter ration fed in a 2:1 hay-grain ratio with two types of hay. Also, the effect of feeding whole milk for either 7 or 9 weeks with and without vitamin B12 concentrate using a 4:1 hay-grain ratio was studied. Comparisons were made also of differences in calf performance and efficiency of feed utilization to 6 months of age between two different hay-grain ratios used in these experiments. During past years several systems of calf feeding have been developed which were aimed at a reduction in milk consumption. In these systems, notably the Cornell and New Jersey systems, the approach has been to use a calf "starter" concentrate mixture containing milk by-products and other sources of animal protein and vitamins as a substitute for whole milk. In contrast, the aim in the high-roughage system has been to develop mature type rumen function as early as possible and in so doing eliminate the need for a calf "starter" in meeting the nutritional requirements of the calf. When rumen function is adequately developed, the products of rumen digestion and synthesis may be considered as a natural replacement for milk. Considerable evidence has been accumulated which indicates that normal health is difficult to maintain in young ruminants without adequate roughage