Alkalage analysis must be correct

28 September 2001

Alkalage analysis must be correct

LAB analysis of Alkalage must take account of cereals later harvest date than other whole-crops to avoid underestimating protein and starch content.

There is nothing new about whole-crop, its a mixture of wheat grain, chaff and straw, Lancs based independent feed consultant Alan Sayle told Dairy Event visitors.

"However, Alkalage is different to other arable silages having a higher starch content and it contains ammonium bicarbonate. This means Alkalage should be analysed differently to fermented and urea-treated whole-crop."

Mr Sayle, together with Volac, launched a free checklist at the Dairy Event to help producers obtain an accurate analysis of their Alkalage.

Current methods involve drying the silage sample before analysis, but this drives off ammonia, so protein content is underestimated. Protein should be analysed before drying the sample for further tests, he advised.

In addition, ammonia loss can lead to a reduction of pH once the sample is opened, said Volacs Naomi Gardner. "Silage pH should be measured immediately after labs receive the sample."

Another problem highlighted by Mr Sayle is grinding the sample before analysis, so results include whole grains which would pass straight through the animal undigested. This will overestimate starch available to cows.

Some labs estimate starch content of arable silage using fibre content, but this can be inaccurate. Starch should be analysed to give a true picture of nutritive value, said Mr Sayle.

Energy content of whole-crop silage is currently estimated using the same equations for maize silage. While this is not ideal, it is the best available at present and research is needed to develop more accurate methods, he added. &#42

Labs could underestimate Alkalages feed value if the correct analysis procedures are not used, says Alan Sayle.

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