The Effect of Fat Upon the Digestion of Nutrients by Dairy Cows

Abstract

Digestion studies were conducted comparing the effects of different levels and different sources of fat upon the apparent digestibility of nutrients in the rations of dairy cows. The differences in fat intake were obtained by using concentrates of different ether-extract content. Timothy hay and dried beet pulp were also fed. There was no difference in the apparent digestibility of rations containing 1.6 and 2.6 per cent ether extract. The difference in fat level of these two rations was obtained by using concentrate mixtures containing 1.8 and 4.4 per cent ether extract. Using soybean products as the sole concentrates, rations containing 1.0 and 7.0 per cent of ether extract were studied. The crude fiber and nitrogen-free extract of rations containing soybeans and solvent-extracted soybean meal plus corn or soybean oil were less digestible than the crude fiber and nitrogen-free extract of rations containing solvent-extracted soybean meal. The ether extract of rations containing soybean meal plus oil or plus fatty acids was more digestible than the ether extract of a ration containing soybeans. Although protein digestibility was lowest on the soybean ration and highest on the ration containing soybean meal plus fatty acids, the significance of the difference in protein digestibility was questionable. The ration containing soybeans caused a marked increase in fat percentage with practically no change in milk flow. The rations containing either oil or fatty acids caused a pronounced decrease in milk flow with little change in fat percentage. The production of milk fat and fat-corrected milk, bore no consistent relation to the actual intakes of ether extract and total digestible nutrients.