Effects of the Extent of Heating Before Ensiling on Proteolysis in Alfalfa Silages

¹ Estación Agricola Experimental, Apdo 788, 24080 Leon, Spain
² Departamento de Productión Animal, Facultad de Veterinaria, Leon, Spain

Two experiments were carried out to evaluate the effect of extent of dry heating before ensiling on the protein conservation of alfalfa silages. A fourth cutting of mature alfalfa was ensiled in the laboratory in both experiments. In Experiment 1, the effects of no heating and of heating for 1 h at 40, 53, or 78°C, avoiding the loss of moisture, were examined. Heating reduced proteolysis. Silages heated at 53 or 78°C had protein contents significantly higher than those of the control silages. Furthermore, the silages heated at 78°C had higher protein N contents than silages at 40°C. Heat reduced N solubility and may have denatured and fixed proteins. Nitrogen fractions bound to NDF or ADF increased, but the N content of the lignocellulose fiber never reached the levels indicative of heat damage. In the second experiment, increasing the heating times to 1, 2, or 6 h at 60°C for silages without additives or with formic acid or formalin was tested. Heating for 1 h before ensiling conserved protein in the control and formic acid silages (46 and 38%, respectively). Further increases as a result of the longer heating times were negligible. Less significant was the effect of heating on formalin-treated silages.

Key Words: alfalfa silage • proteolysis • heating treatment

Submitted on September 30, 1991
Accepted on February 24, 1992