Effect of Hay to Grain Ratio on Utilization of Metabolizable Energy for Milk Production by Dairy Cows

Abstract

Indirect calorimetry was used in total energy balance trials with six mature, lactating, nonpregnant Holstein cows to study the utilization of metabolizable energy (ME) for milk production. An orthogonal set of 3 × 3 extra-period Latin-squares was used. The three rations fed contained 50% (A), 75% (B), and 100% (C) wafered alfalfa hay, based upon estimated net energy (ENE) values, and 50% (A), 25% (B), and 0% (C) of a mixture of corn meal and soybean oil meal. The rations were offered on an equal ENE basis. More ME was required for milk plus maintenance from the all-alfalfa ration than was required from a ration of alfalfa and concentrate when the ME was regressed on milk energy. The treatment means were adjusted to a common milk energy output by covariance analysis. When the maintenance requirement was assumed to be 131 kcal ME/kg3/4, and tissue gain or loss was adjusted to zero balance using the factors 1.61 kcal ME/kcal tissue gain and 1.43 kcal ME/kcal tissue loss, the mean efficiencies of converting the available ME to milk were 65, 61, and 54%, (P < .05) for rations A, B, and C, respectively. © 1964, American Dairy Science Association. All rights reserved.