Big gaps in silage results

By Peter Young

Want better quality silage? Send your grass silage samples to Hillsborough.

That's the finding of a survey of silage samples the Irish Farmers Journal collected on twelve farms. The Journal split the samples and sent a half of each sample to the two main silage-testing laboratories in the country; The Agricultural Research Institute, Hillsborough and Farm Business Advisors Laboratories in Fermoy.

The process was carried out to answer farmers' growing concerns about where they should send their silage samples to be analysed.

The averages show that Hillsborough is reporting higher values for all the major parameters. DMD (Dry matter digestibility), one of the most important values, is on average 3 DMD units higher, dry matter was 1.28 per cent higher and crude protein was 1.33 per cent higher for the Hillsborough results.

The difference between laboratories for specific samples was even greater. Looking at DMD the difference between specific samples was as high as 6 units DMD. Using Teagasc figures this is equivalent to a difference in production of 2.27 litres (0.5 gallon) per day and a difference in milk protein of 0.1 per cent a day when the silage is fed to a dairy cow.

In beef, a difference of six units DMD would change average daily gain by 0.2kg/head/day. To make up this difference the farmer would have to feed 2kg concentrates.

At 15p/kg meal, that is £30/head difference in feeding costs over a 100-day feeding period. Taking the differences in crude protein between labs could increase this cost even further.

The most startling difference is when you look at the amount of milk that the silage will produce if eaten as the sole diet.

The Hillsborough system is predicting that the silages would produce on average 3.3 litres (0.72 gals) of milk more than the FBA labarotory results. In one sample the difference between the two labs was a massive 8 litres (1.8 gals) of milk per day.

"We would be very confident that our system gives the best available analysis. However silage sampling is an inexact science," said Professor Fred Gordon, Hillsborough.

"DMD is not a direct measure but a prediction of digestibility. Milk production is also greatly affected by intake".

Silage sampling is a good guide to how your silage compares with previous years. The ranking of the silages between labs was close with good silages coming out on top. The results show that similar results for pH was also reported by the labs, an indication that there are not major errors occurring.

Who is correct? That is the problem for farmers. You do not know what the quality of the silage really is therefore you do not know which lab is right.

Given the differences uncovered it is important that farmers and also organisations giving feeding advice work out of the same laboratory every year. Alternatively a regular system should be put in place to allow adjustments between labs.