AN EVALUATION OF STEAM-TREATED ASPEN AS A SUBSTITUTE FOR CORN SILAGE IN THE RATIONS OF LACTATING COWS

Abstract

Fifteen lactating Holsteins were used to test processed aspen added to corn silage at the levels of 0, 10 and 20% (dry matter basis). The experiment was designed as a latin square with three experimental periods each 42 days in length. The forage mixtures were fed free choice to the cows, which were housed in a free-stall barn, and their individual feed intakes were recorded by using electronic doors. The processed aspen contained 45.4% dry matter, 73.7% acid detergent fiber and 0.54% protein. There was no evidence of heating or mold growth in the aspen during the 5 mo of the trial. Silage dry matter intake and milk yield were 11.8, 13.4 and 13.4 and 25.7, 27.0 and 26.8 kg per day, respectively, for the silage mixtures containing 0, 10 and 20% processed aspen. Fat test was decreased slightly and milk protein content significantly (P < 0.05) depressed by the addition of 20% processed aspen chips to the corn silage. Efficiency of milk yield was not significantly influenced (P > 0.05) by the inclusion of aspen chips in the silage. Neither the molar proportion of acetic acid nor the ratio of acetic acid to propionic acid in the rumen fluid was changed when the cows were fed silage containing processed aspen chips. The apparent digestibilities of total ration dry matter and protein were lowered significantly by the addition of 10% aspen chips to the forage mixture. It was concluded from the results of this trial that steam-processed aspen chips had little nutritive value when fed to lactating cows as a partial substitute for corn silage.