Many farmers will be eyeing up their second cut of silage in the next few weeks, and silage test results should have an influence on when to start cutting.
The biggest variation in silage test results and particularly silage dry matter digestibility (DMD) stems from the date the crop was cut – which has to be at the back of every farmers’ mind as second cut approaches.
Realistically, farmers are only going to need dry cow silage for about 10 to 12 weeks of the winter. The remaining weeks and into the spring are going to require a higher quality silage for milking cows.
Milking cows are going to need at least a 74% DMD silage for the few weeks they may be housed, as well as for the shoulders of the year when they are getting buffer fed or they need extra silage to support grazing during poor growth.
When talking about silage quality, the focus is often just on DMD and crude protein, but Teagasc have highlighted that good fermentation characteristics to ensure palatability and support high dry matter intakes are also crucial.
Silage test results
Conducting a silage test is a simple and cheap, and will give you very valuable information on this year’s feed along with good guidance on what to improve for the next cut of silage.
The DMD of your silage for dry cows should be between 68-70% and over 74% for milking cows and young stock. The DMD of silage is the key determinant of the overall feed value.
When it comes to the UFL of your silage – which is an indicator of energy, as the higher the UFL, the more feed energy for milk solids – dry cow silage should be between 0.72-0.75UFL/kg. and milking cow silage from 0.83-0.88 UFL/kg.
The crude protein of silage can be impacted by the DMD of the silage and the timing and quantity of nitrogen applications. It should be over 12% for dry cow silage and over 14% for milking cow silage.
The PDIE – which is the digestible protein in the small intestine – should be 75g/kg for dry cows and over 80g/kg for milking cows. This is determined by the UFL and crude protein levels in the silage.
The intake value of the silage should be between 90-95g/kg LW (live weight)0.75 for dry cow silage and over 105 g/kg LW0.75 for milking cow silage.
The potassium (K) content should be less than 2.2% for dry cows, as high K silage fed from two weeks pre-calving creates a milk fever risk. For milking cows, if the K content is over 2.4%, there should be no issue.
Moving onto preservation metrics, the pH of your silage should be between 4.0 to 4.2 and up to 4.4 for drier crops. If the pH is too high, it indicates poor preservation and if it is too low, intakes may be affected.
High ammonia also indicates poor preservation and reduces intake, so it should be less than 8% nitrogen.
Higher values of lactic acid indicate a stable and palatable silage as ideally it should be between 8-10% of lactic acid DM while high ash indicates soil contamination and should be less than 8% DM.
Remaining cuts
Many were able to exploit the good weather in early to mid-May this year, which allowed for a balance to be struck between a decent yield with high quality, digestible green leaf in the sward.
This balance needs to continue for the next couple of silage cuts on the farm. Waiting for more bulk will decrease the quality of the silage and take away from the yield of the following cut.
As the proportion of stem in poor quality cut increases, it will negatively impact on digestibility and the protein supply from he silage.
Many farmers were left with extra silage in their yard after the winter this year, but was that because it was poor quality silage and cows’ intakes were limited from the amount of fibre in the forage?
Fibrous silage that has a limited amount of crude protein and is not very palatable or digestible will affect cow performance ad limit intakes.
Testing silage every year should be done on every farm, so that the farmer understands the nutritional implications of the feed available to them.
