Unidentified Dietary Factors in Dairy Cattle Nutrition. I. Digestibility of Peanut Hulls and their Use in “Ballast” Studies with Milking Cows Depleted on Hay Alone

Ever since the work of Kellner and Khhler (20), it has been universally recognized that a pound of total digestible nutrients (T.D.N.) in roughages, other than young pasture and hay grown in certain areas in the Rocky Mountain region, was inferior for production purposes in the ration of livestock when compared with rations of roughages plus concentrates. Kellner and Khhler concluded from the results of their studies with steers that the productive value of feeds varied more closely with the crude fiber content than with any other ingredient in the feeding stuff. Consequently, a method of feed evaluation was worked out which was based on the crude fiber content and expressed as starch equivalent. Armsby (2) calculated net-energy values for many feeding stuffs by discounting the digestible nutrients on the basis of the amount of crude fiber. Woodman and Evans (29) determined starch equivalent values by deducting 0.58 times the undigestible crude fiber from the T.D.N. value. Lehmann (21) used undigested organic matter as an index of "ballast" as the basis for a discount system for calculating net-energy values. In 1932, Forbes (6) stated the modern concept of a balanced ration as follows: "--there is no present, or possible scientifically significant and defensible single measure of nutritive value of individual feeding stuffs; and that in order to place our interest in such a measure on a rational basis it is necessary to revise the terms of the interest itself, and to base it on rations as wholes 2 rather than upon individual feeding stuffs."