Grass silage is the predominant feed used on the vast majority of beef farms in Ireland, so the quality of the feedstuff available in your yard cannot be ignored.
Over or underestimating feeding value due to a lack of test results can cost you a significant amount of money. Heavy rain in recent times has led to cattle being housed on many farms – particularly on farms with heavier soils.
If this forage is not analysed, then farmers will either underestimate or overestimate the amount of meal and/or silage required by stock in order to secure optimal animal performance.
Taking the sample
The target is to end up with an accurate sample and the tool required is called a sampler or core. Samples should be taken from the highest point on the pit with the sampler driven down to the bottom of the clamp.
The top five inches of forage from each core should be discarded with the remainder placed in a container.
Up to seven cores will be required from each silo. These should be mixed together and a representative sample then drawn off.
Holes created in the plastic must be taped up, in order to prevent forage degradation. When testing bales, it is standard practice to core two from each batch made in order to get a representative sample.
Once the required samples are prepared, they should be submitted for analysis. Teagasc and feed compounders will do this automatically on behalf of clients.
Alternatively, individual farmers can drop their own silage samples in at their local Teagasc office or meal supplier. The cost of a standard silage analysis is in the range of €25-35.
Interpreting The Results
1. Preservation
Well-preserved silage is more palatable and will result in higher animal intake and performance. Well-preserved silage should have a pH of 3.8-4.2 (up to 4.7 for dry, baled silage).
Ammonia (NH3) levels of less than 10% are also desirable, while values greater than 15% indicate bad preservation.
2. Dry matter
Intake will be higher on high dry matter (DM) silage of +20%. Silage made during broken weather will have a lower percentage DM.
3. Digestibility
Digestibility (DMD%) is an accurate and reliable test of forage feeding value. The result is used to estimate energy value, expected live weight gains or milk yield and required supplementation rates.
Young perennial ryegrass swards cut for silage after six weeks of growth should have a DMD% of 75-80%, while older, stemmy swards when cut would have a DMD% of 60-65%.
4. Crude protein
The crude protein percentage reflects the quality of the grass at harvest, with young, leafy grass having values of over 15% and stemmy grass with values of less than 10%.
5. Minerals and trace elements
A more detailed analysis can also be carried out to look at the mineral and trace element make-up of the silage.
The main elements tested for are: calcium; potassium; phosphorous; magnesium; sodium; and sulphur. Where trace minerals are concerned, the elements of interest are: copper; zinc; manganese; molybdenum; iodine; cobalt; and selenium.