Peripheral Spoilage on Exposed Silage Pile Faces: What is the Cause?
Adapted by Peter Robinson, UCCE Dairy Nutrition Specialist & Nadia Swanepoel, Dept. of Animal Science
Corn silage is an important ensiled crop in most dairy areas. However, spoilage during the ensiled period is an economic loss to dairy farmers. One of the critical points to control spoilage in silage is to limit oxygen entry to silage since it supports growth of aerobic microorganisms and the resulting heat production can lead to silage with degraded nutritional quality, as well as enhanced shrink losses. A relatively simple practice which has gained wide use on commercial corn silage piles is use of a thin inner plastic film with enhanced oxygen barrier (EOB) properties between the silage mass and the main plastic cover.
We related results of a study using 4 corn silage piles in the January issue which showed that pliable polyethylene film (POLY) and EOB silage underlay films had similar impacts on measures of silage deterioration of corn silage pile surfaces prior to opening, or during pile feedout, as well as ~25 inches under the pile surface at the exposed face or in the deep silage mass of the pile. Indeed both underlay films were associated with well-preserved silage with little sign of deterioration.
However, because the surface 20 inches in direct proximity to the exposed face had deteriorated regardless of underlay film used, further investigation was undertaken to determine why it was occurring. The results of this investigation are discussed below.
So how is Peripheral Face Spoilage Occurring?
An ~2,000 ton pile of corn silage was constructed to examine the progression of spoilage into the silage pile from the exposed face during pile feedout, as determined by sampling the silage under the undisturbed plastic cover up to the exposed face in two coring events which separated by face silage removal (Figures 1 and 2).
At the point when the exposed face was ~80 feet from the beginning of the back ramp slope, both sides and the back ramp of the pile were cored to 20 inches in two segments of 10 inches each according to the grid in Figure 1. The pile was re-cored 69 days later using the same procedures, except that some core points no longer existed due to silage removal (Figure 2). Face management at the second coring was similar to that at the first.
At the first coring, the outer (versus inner) cores had higher pH, temperature and mold/yeast counts at locations nearest to the exposed face. At the second coring, when four previously cored locations no longer existed due to silage feedout, the outer (versus inner) cores had higher pH, temperature and mold/yeast counts at locations nearest to the exposed face – as at the first coring – although these actual core points had no sign of deterioration at the first coring.
In general, silage spoilage was impacted by location and surface depth relative to the exposed face at the first scoring had simply ‘migrated’ into the pile with pile use.
What Have We Learned?
Surface spoilage during pile unloading was ‘moving’ with the exposed face such that silage ~24 feet back of the cut edge of the cover plastic had seriously deteriorated in the outer 10 inch core, with no deterioration ~44 feet back of the cut edge of the cover plastic, regardless of coring event.
It is clear that deterioration of corn silage (often visible on the periphery of the exposed face at pile unloading) is primarily a function of its exposure at the face rather than on the surface of the pile while it is under the silage pile plastic cover prior to pile opening.
Silage deterioration at the exposed silage face appears likely to be minimized by increasing speed of exposed face movement over the ground, and/or use of moveable weight lines directly behind the exposed face to limit entry of air to the pile between the plastic cover and silage surface at the face.
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