By now, farmers across the country are probably worn out at the thoughts of completing fodder budgets and listening to advice around measuring silage stocks and calculating winter feed demand.

With all this concern around the quantity of silage in the yard, one element that has possibly been forgotten about is the need to test for silage quality.

But what is this important? Well put it this way, every dairy farmer certainly knows the protein content of their dairy nut for example. And every beef farmer will certainly know the energy value of their beef ration too.

With that in mind, silage is still the main component in most winter diets across beef, dairy and sheep farms in Ireland so there is no logical reason why you shouldn’t know the feeding values of this feedstuff, just like every other ingredient you bring into your yard.

Silage sampling should take place six weeks after ensiling to ensure full fermentation has 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 fresh weight silage an animal eats. In general, lower DM silage will have lower intakes and higher DM silage will have higher intakes.

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

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 dryer the grass, the more energy the silage will supply for milk production and liveweight gain.

DMD value

This is a measure of the feeding value of the silage expressed as a percentage. Late cut, old swards can have a DMD as low as 55DMD while excellent leafy silage can be > 75DMD. Silage with a high DMD will be digested quicker and lead to higher intakes.

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 8-10% 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:

  • Young grass: 45-50%
  • Average: 55%
  • Mature grass: 60-65%

    • 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.