The Comparative Value of High and Low Fat Concentrates with Alfalfa Hay

In the alfalfa-producing areas where cows, to a great extent, are fed solely on alfalfa hay, milk production is only 50 to 85 per cent of that of cows fed alfalfa hay with grain supplements.The restricted production on alfalfa hay alone is due either to the absence of some nutritive element or elements in the alfalfa hay or to a lack of sufficient total digestible nutrients.In an effort to determine what was responsible for this subnormal production of cows on alfalfa hay, Smith et al. (11) replaced a part of the alfalfa hay with equal amounts of total digestible nutrients in concentrates and noted that the greatest stimulus to milk and butterfat production was obtained when ground soybeans were fed.Since there was a greater stimulus from feeding equal total digestible nutrients in ground soybeans than from soybean meal, the question arose as to whether the stimulus resulted from protein supplementation or from the additional fat supplied.Evidence of a conflicting nature has been presented in the literature on the effect of a ration high in dietary fat on milk and butterfat production of the dairy cow.Bratton et al. (1) found inclusion of raw soybeans in amounts equal to 25 per cent of the grain ration caused a measurable increase in the butterfat test of the milk produced.Williams et al. (13) found that cows on an all-soybean ration produced milk with a significantly higher percentage of butterfat than did cows on normal feed.Loosli et al. (4), Maynard and McCay (5) and Maynard et al. (6,7,8) have conducted many experiments on the influence of dietary fat on milk and butterfat production.These workers concluded that the main effect of a ration high in fat is to increase the amount of milk rather than to influence the fat component of the milk.Monroe and Krauss (9), feeding grain mixtures varying from 2.69 to 4.89 per cent fat, found no differences in the production of milk, butterfat or 4 per cent fat-corrected milk.Gibson and Huffman (2) reported that whea soybean oil was added to a basal ration low in fat, an increase in milk production resulted.They also reported a temporary increase in butterfat percentage.The study repoxted in this paper was undertaken to investigate further the effect on milk and butterfat production of feeding a supplement high in dietary fat to cows receiving a basal ration of alfalfa hay.