Testing silage is key to forming a well-formulated, energy rich diet to drive milk production for your winter milk herd.

Many farmers have got out of winter milk/liquid milk production in the last number of years due to higher input costs and shortage of labour in the country.

So, it is no secret that winter milk production is already an expensive way of producing milk.

This means it is crucial that farmers test silage, as silage quality is the key to good animal performance and the cheapest way of producing milk in the winter.

Having good quality silage will allow farmers to produce milk from mainly silage, which will reduce winter feed costs and increase profitability during the housed period.

Grass silage is the basis of most winter feeding systems, with good animal performance is largely down to an adequate intake of quality silage.

If silage results are obtained, it will allow farmers to add adequate meal or other feed sources to make up the energy requirements of the herd.

In general, when more meal has to be added to the cows' diet during the winter milking period, it is to make up for poor quality silage.

To ensure your cows are meeting their energy requirements and milking to their full potential, you must know your silage quality so you can make a winter feed plan to make cost-effective decisions on concentrate supplementation.

Concentrate feeding to support milk yield based on silage quality, according to Teagasc, is as follows:

The table above highlights the amount of extra meal that will be required to make up for the poorer quality silage, with an extra 4kg/meal /cow/day needed to produce the same amount of L/cow when feeding 75% DMD compared to 79% DMD.

Silage testing is still not a frequent practice on many dairy farms, but farmers should ask themselves: "Would I be happy if I received a delivery of concentrates without getting information on its ingredients or feed value?"

The fact is, your silage quality is far more important in terms of the cost and performance of the winter diet.

Silage that is made in poor conditions could leave it with a low dry matter (DM), low digestibility, low crude protein (CP), high ammonia levels, and high acidity.

This will result in cows having low DM intakes and poor animal performance, which will lead to farmers compensating in the form of concentrates, maize, whole crop, and/or beet, which is going to drive up costs.

In terms of quality, for dairy cows in milk and growing heifers, DMD (dry matter digestibility) should be at least 72%, and 75% for freshly calved winter milking cows, while dry cows in need of moderate body condition score (BCS) gain will need silage at 68-70%. 

The UFL (energy) for milking cows and young stock should be 0.83-0.88 UFL and the CP level should be above 14% - lower DMD and/or nitrogen (N) application will reduce your CP.

The PDIE - which is your metabolisable energy supply - is determined by your UFL and CP levels in the silage, and should ideally be at 80g/kg.

The intake value will indicate the silage intake potential and should be over 105g/kg for cows that are milking during the winter.

Potassium (K) content of silage should be noted, as high K silage fed from two weeks pre-calving will increase the chances of milk fever occurring, and so should be less than 2.2% pre-calving and during lactation. Over 2.4% will pose no risk.

A simple, cheap test will give the farmer valuable information on this year's feed and will aid in making a plan for this year to bridge the nutritional gap in the most cost-effective way.

Silage should be costed on a DM basis, and when silage is well preserved and cut in good conditions, the DM should be anywhere between 24-28%.

Too high of a pH points towards poor preservation, while a too low could affect the cows' intake. Ideally, pH should be 4.0-4.2.

Likewise with ammonia levels in silage, as high ammonia will indicate that the silage was poorly preserved and will have a knock-on affect on intake.

Ammonia should be less than 8% and lactic acid levels should be 8-10% of DM, with higher levels indicating a stable, well-preserved, palatable silage.

Ash should be less than 8% of DM - higher levels indicate a soil contamination issue on the silage ground.

Farmers should aim to maximise the amount of milk produced from forage, which will reduce the amount of bought-in supplementation.

If the test does show that silage quality is poor, farmers can account for this and feed extra in order to not hinder the cow's performance, aiming for a 15.5-17% crude protein in the overall diet.