Q. What's the effect of packing density on dry matter loss?
A. First, let's look at what packing does. To get the anaerobic ensiling fermentation started and to minimize the aerobic spoilage processes, we need to get rid of all the oxygen "trapped" in the forage. This is achieved through packing the forage efficiently to drive air (oxygen) out and by the residual oxygen being used up by microbial growth and plant respiration.
When forage isn't efficiently packed, plant respiration is extended, which increases heat production and nutrient losses. — Aerobic organisms then grow, reducing the quantity of sugars available for the desirable lactic acid-producing organisms, increasing the nutrient losses and resulting in higher residual numbers of aerobic spoilage organisms in the silage at opening. Poor packing therefore causes problems both at ensiling and feedout, resulting in increased DM and nutrient losses and reduced silage quality.
Silage density results from packing intensity, including packing layer thickness (no more than 6"), and crop dry matter (DM) at harvest. With a few simple measurements, producers can estimate the average density of forage in various storage units using a calculator spreadsheet from the University of Wisconsin at http://fyi.uwex.edu/forage/harvest/.
Despite the importance of packing, the density achieved on commercial operations has been shown to vary considerably.
We recommend all producers take the time to understand what is involved in getting the silage packed well, and make sure that all their silages are packed efficiently to drive out oxygen from their forage at harvest. It can make a huge difference in limiting DM and nutrient losses and maintaining forage quality.