Effects of Silo Type on Ensiling Alfalfa

Abstract

Abstract. Various silo types are used on dairy farms, but there is uncertainty as to how silo type affects silage losses and quality. The objective of this study was to compare three silo types, filled with alfalfa from the same fields and emptied simultaneously, relative to filling rates, dry matter (DM) losses, and silage quality. Similar trials were performed in two consecutive years where second cutting alfalfa was harvested in late June and ensiled in three silos: bunker (4.9 A— 21.3 A— 3.5 m), bag (2.4 m dia. A— 52 m), and oxygen-limiting tower (4.3 m dia. A— 15.2 m). Approximately half of the forage from each field in each trial was ensiled in the bunker silo, and a quarter was allocated to the bag and tower silos. All three silos were filled over approximately a 24-h period with target DM concentrations of 35% to 40% for the bag and bunker silos and 45% to 50% for the tower. For each load, weight and times for filling and packing were recorded; a sample was taken for DM and nutrient analysis. The following summer, all three silos were emptied over approximately the same dates. Daily silage samples from each silo were composited weekly for analysis, and the weights of all silage removed were recorded whether fed or not. Filling rates (Mg DM per h) were similar for all silo types using the established management practices and equipment at the research farm. Over the two trials, average DM losses from the bag, bunker, and oxygen-limiting silos were 11%, 17%, and 4%, respectively, for 14 to 15 months storage. There were few effects of silo type on nutritive characteristics such as crude protein (CP) and fiber fractions of the alfalfa silages in the first year when fermentation + respiration DM losses varied over a narrow range across silos. In the second year where the bunker silo had the greatest fermentation + respiration losses, CP was reduced and fiber fractions were increased in the bunker silage compared with those in the silages from the other two silos. Small effects in silage fermentation due to silo type were observed in the first year where the DM concentrations were similar across the three silos. In the second year, the best fermentation occurred in the oxygen-limited silo whereas the bunker silo with the greatest losses had evidence of clostridial fermentation beginning.