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

Abstract

Four depleted milking Holstein cows were used to determine the digestibility of hay when fed alone and after 15 lb. of the hay had been replaced with 6 lb. of corn and 9 lb. of peanut hulls. Pour Holstein cows were maintained on the basal hay ration throughout the experiment as controls.The coefficients of digestibility of the peanut hulls were found to be: dry matter, 21.1; organic matter, 21.1; carbohydrates, 20.9; protein, 23.7; ether extract, 13.0; crude fiber, 24.0; and nitrogen-free extract, 10.5. The “ballast” values were calculated to be: undigested dry matter, 78.9; undigested organic matter, 78.9; and undigested carbohydrates, 79.4 per cent.Three of four cows increased in the production of F.C.M. when changed from hay alone to a hay-corn-peanut hulls ration, whereas all of the control cows declined in F.C.M. All of the cows increased in the number of pounds of F.C.M. per 100 lb. of T.D.N. on the hay-corn-peanut hulls ration, while all of the control cows showed a decline.The amount of F.C.M. increased appreciably in spite of the fact that the calculated net-energy and starch equivalent values declined markedly and the crude fiber and undigested carbohydrates increased.The results of this investigation support the modern concept of a balanced ration and illustrate some of the imperfections in both the calculated net-energy and the starch equivalent concepts as scientific methods of feed evaluation.The data presented in this paper give further support to the contention that grain supplies the unidentified factor(s) needed by some hays for more efficient milk production.Undigested carbohydrates appear to be a better index for “ballast” evaluations than either undigested dry matter or undigested organic matter.The losses in body weight of the cows on the hay-corn-peanut hulls ration appeared to be due to a decrease in wet fecal weights due to a lack of fill, although the daily amount of fecal dry matter increased.