Assessment of silage losses

The variability in grass silage quality in clamps from 20 farms in England was examined to see what factors were associated with differences in quality both within a clamp on a single farm and between clamps on different farms.

The height of grass in the clamp, clamp width and length was assessed first.  In addition ambient temperature in front of the clamp was measured as was the geographical orientation of the clamp and the open face.  From the clamp dimensions the sampling points in each clamp were then marked out. At each sampling point, silage density (kg/m3) was assessed using a cored sample.

Top and shoulder ‘waste’ silage was assessed on all farms and samples collected.  The top waste sample was collected by walking across the top of the clamp and taking a core vertical down into the clamp of approximately 30 cm depth every third or fourth step and mixing all cores taken together. These samples were analysed by wet chemical procedures for Dry Matter and Ash.

For clamps, the vulnerable zone is 0.5 m from the side wall or the top sheet of the clamp.  Many farmers disregard this portion of the clamp as being the ‘bits around the side’ but by conducting these evaluations then it is clear to see that a significant proportion and on average 27% of the volume and 21% of the fresh weight of all the silage is in these vulnerable zones. For the clamps assessed, the average cost of filling the clamp was around £21,000, which means on average over £4,000 worth of silage is in the vulnerable zone.

The proportion of the clamp within a 0.5 m of the wall increases as the silage clamp width and height reduces. The crucial factor is management at filling and rapid feed-out and this is true irrespective of clamp size.  The data are presented to highlight the importance of silage in this region to the overall quantity of silage, its effect on losses of both DM and quality and by knowing, management process can be put in place to reduce these losses.

The density of silage in a clamp is a key marker that affects many of the problems associated with storage, Poor density leads to poorer preservation quality and secondary fermentation (not to be confused with aerobic spoilage). This is where products of the primary fermentation normally lactic acid, are converted to secondary fermentation products such as acetic and butyric acids by undesirable silage microorganisms, due to the presence of trapped oxygen at the beginning of the storage period.  Poor density also increases the ingress of oxygen during the entire storage period if sealing is inadequate and finally it increases the risk of aerobic spoilage or deterioration at feed-out due to the ability of oxygen to penetrate further into the silage from the open clamp face.

In terms of waste, nine of the 20 farms had no top or shoulder waste, with the range for the other clamps being 0.2% to 36.7%, which equates to £44 to over £8,000 of lost production due to waste in the clamp.

The Problem:

Silage production in the UK makes up a major proportion of the winter feed on many livestock farms, with an estimated 50 million tonnes (fresh weight) of silage being made annually. However, there are many poor practices and losses of silage DM have been estimated to be between 25-40% in clamps. This costs UK farmers upwards of £170 million.

Aims and Objectives:

Whilst much progress has been made in educating UK farmers about he importance of harvesting good quality forages to produce good silage. There is little information pertaining to the quality of storage of silage on UK farms. The aim of this study would be to evaluate management factors from the point of cutting to the point of feeding that can have a significant effect on silage quality, animal performance and thus greenhouse gas emissions for UK livestock farms.

Approach:

Up to 20 farms across England will be recruited with the focus being beef producers with some dairy farmers included. Each farmer will be asked an extensive questionnaire with a  number of questions asked covering the whole management of their clamp silages from harvest to feed-out. Silage Solutions Ltd staff will conduct two visits as their assessment must be standardised across all farms.