How to read your silage sample results

Silage sampling should take place six weeks after ensiling to ensure full fermentation as occurred. Once you get the returns of your silage sample, the report will give a breakdown of several key silage quality measures. Here are some of the main ones and what they mean:

Dry matter (DM)

This is the amount of matter remaining after all water has been removed. The energy and protein value of silage is quoted in %DM. The higher the DM, the higher the intake of energy and protein will be for every 1kg of freshweight silage an animal eats. In general, lower-DM silage will have lower intakes and higher-DM silage will have higher intakes.

DM% can be as low as 15% and as high as 45%. Somewhere in the middle (25% to 30%) is optimum.

DMD value

This is a measure of the overall feeding value of the silage expressed as a percentage. It is arguably the most important measure. Late-cut, old swards can have a DMD as low as 55% while excellent leafy silage can be >75% DMD. Silage with a high DMD will be digested quicker and lead to higher intakes. Anything over 70% DMD is good.

pH

A well-preserved silage should have a pH of between 3.8 and 4.2. Wet silage, with a high pH, will not keep as well and will usually indicate a silage that has not fermented well and silage intakes will be low. If pH is below 3.8, this can lead to acidic conditions, a sharp smell and cows throwing up “cud balls”. Dry silages can have a higher pH and good preservation.

Ammonia levels

High ammonia levels show poor preservation. This can be due to high grass nitrogen levels at cutting or low sugar possibly from wet young grass being cut. Values of <5% indicate excellent preservation, while >15% will lead to reduced intakes.

Crude protein

This measures the protein concentration of the silage. Young leafy reseeded swards will have higher protein values. Inadequate fertiliser applications can lead to lower protein levels. Values >15% indicate young leafy swards.

ME (MJ/kgDM)

This is the amount of energy in the silage. Young grass will have the highest energy while mature grass will have lowest energy. The younger and drier the grass, the more energy the silage will supply for milk production and liveweight gain.Over 10MJ/kgDM is good.

Lactic acid %

Bacteria in fresh silage uses grass sugar to make lactic acid which aids the ensiling process by pickling the silage. Cutting young grass in sunny conditions will lead to high lactic acid %. A well-preserved stable silage will have a high % of lactic acid. Levels of 8% to 12% are classified as very good.

Neutral detergent fibre (NDF)

This is a measure of the total fibre content in the silage. Late-cut, mature, stemmy silage will have a high NDF. Typically NDF values depending on grass type would be:

Intake value

This is a relative measure of the likely intake of silage. HFIS is the unit measure for beef cattle. This can range from 50 to 105 and a high figure indicates high DM, high DMD and low ammonia.

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