Estimating Silage DM Can Be a Risky Business
2009-10-28

Estimating the dry matter content of silage is much harder than many farmers and forage consultants think, according to the results from a challenge laid down by Sciantec Analytical Services at this year’s Dairy Event.

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The company, which specialises in the provision of forage and other analytical services, asked visitors to use their skill and experience to estimate the Dry Matter (DM) content of six different silage samples on display on their stand.

The samples had previously all been tested in the laboratory using the standard wet chemistry method for silage DM.

“Comparing the actual DM content as analysed in the laboratory with the estimates made by visitors to the stand underlines just how difficult assessing DM content can be,” says Linda Forbes, one of Sciantec’s Business Development Managers. “Many of those who participated have years of experience and even they found it difficult, especially when it came to estimating the higher DM silages,” she adds.

As the table shows, the average estimates for the two highest DM silages (actual DM values of 61.3 and 55.2) were just 49 and 37.5 respectively. If both cases the contribution from the silage was effectively undervalued which if this had happened in the field is likely to have led to inflated feed bills.

At the lower end (actual DM contents between 27.2 and 24.9), the average estimates were much closer to the actual figures. However, the averaging process hides a wide variation in individual estimates. For example, the sample with an actual DM of 27.2 was estimated at levels between a maximum of 60 and a minimum of 17.

“Many of the people who gave us their estimates were experienced consultants and farmers who regularly tackle this question in the field,” explains Linda. “Whilst it was only intended as a bit of fun at the event it has clearly demonstrated that in-field assessments are fraught with difficulties.”

The most reliable way of valuing the nutritional contribution from silage is to test the sample. Silage analysis costs just £13.50 – an investment worth making.

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