Predicting Total Digestible Nutrients and Estimated Net Energy of Dairy Cow Rations from Chemical Components

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Abstract
Rations (14) varying in composition were fed in measured quantities to satify appetites of Holstein cows from calving through 6 or more mo. of lactation. Milk yield and energy intake increased as available energy content of rations increased, but intake of dry matter was not related to milk production. The requirements for total digestible nutrients and estimated net energy of the average cow fed each ration were calculated from published requirement factors. Energy requirements were divided by amounts of dry matter consumed for each of the 14 rations. These energy values were regressed on crude fiber contents of rations either alone or with the crude protein contents to derive prediction formulas to calculate the total digestible energy or estimated net energy of rations. Estimated net energy is estimated net energy as the average megacalories/kilogram of ration dry matter to support all energy needs.