Errors in Drying Silage and Feces for Protein and Energy Determinations. Improved Procedures

N~w Hampshire Agrie~dt~tral Experiment Station, DurhamNutrient losses during drying were less in sflages which were preserved with molasses, sulfur dioxide, or sodium metabisulfite; whereas, those unpreserved lost considerable protein.Editor.Livestock men, dairymen in particular, realize that one of the keys to profitable production is the maximum use of high-quality forage, harvested at the proper stage of maturity and stored so as to reduce as much as possible the nutrient losses which result from poor methods of handling and adverse curing weather.Because the making and feeding of silage, both corn and grass, appear to be a good solution to this problem, the nutritive evaluation of silages has become increasingly important in recent years.The two principal criteria of the nutritive value of a silage are its digestible protein content and its digestible energy content.To arrive at these two values, one must determine the protein and the energy contents of both the silage fed and feces produced.Protein usually is determined on dried samples of silage, and feces by the Kjeldahl method, although a few workers have used fresh material.Gross energy generally is determined by burning dried silage or feces in a bomb calorimeter.This procedure has been improved upon (1,2,3) by passing the volatile gases from the drying silage through a tube furnace and collecting the products in an absorber train.Results were calculated as acetic acid, and the energy value of the silage was corrected accordingly.These methods are tedious, and subject to errors resulting from leakage .in the system and to assumptions which have to be made.The authors became concerned about possible errors in currently used methods during 1951, when it was found that both protein and energy of silages were less digestible than the protein and energy of hays made from the same field at the same time; but that dairy heifers fed the silages retained considerably more protein and energy in spite of this apparent lower digestible nutrient intake.This was supported further by the fact that heifers fed silage gained more in :