In general this year, much to the surprise of many farmers, silage quality is not as good as 2013. This year, average dry matter digestibility (DMD) results from the Agri-Food and Biosciences Institute AFBI are coming in 1.3% below 2013 results.

Many silage samples are low in dry matter and low in overall energy. According to AFBI, this means winter milkers cannot take as much milk from forage, and ultimately will have to feed extra concentrate to compensate. For dry cows to maintain condition, a silage with a DMD of 68 is needed through the winter.

The experts at AFBI said: “This year, first-cut silages were late, and wet in many cases, so low dry matter (DM) and low energy (ME) silages were made. Grass tended to be more mature at cutting (even if cut at usual time) so DMDs of first cuts are down.”

Silage analysis is extremely important for winter milk farmers to know what sort of energy levels they are feeding their stock and if supplementation is required. If energy levels are too low, milking cows may burn energy reserves over the winter. On the other hand, if energy levels are higher, excessive meal feeding of cows may not be necessary.

It is only by taking samples and sending away for analysis that you will be able to judge whether you need to supplement cows or reduce their intake of silage. The following paragraphs explain the basics.

Silage pH

The pH of a silage is a measure of the acidity of a silage. A pH of 3.8 to 4.2 is best and will show silage that is preserved and will keep well. A low pH value may indicate very acidic silage and may require buffering to avoid stomach upsets such as acidosis. Silages that have a pH greater than 4.5 may be poorly preserved, but on the other hand some well-preserved wilted (very dry silages) may have a high pH and be perfectly good.

Dry matter %

This is a measure of the amount of silage remaining after the water has been removed. Water has no feeding value – that is why we exclude it. The higher the dry matter, the more energy the animal will receive per kilo of silage consumed.

Dry matter digestibility

The DMD% is the best indicator of silage feeding value. This will show the amount of utilisable energy in the silage. Good-quality leafy grass cut in good conditions in early June should have a high DMD of 75, while silage cut in poor conditions and late when the crop is gone to head will only have a DMD of 60 or less.

Crude protein %

A measure of how mature grass was at the time of cutting.

  • >15% – young leafy grass (possibly from a leafy young grass)
  • 11-15% – grass at normal stage of cutting.
  • 7-11% mature stemmy crops.

    • NH3 % of total N

    This figure can be used to determine the state of preservation of a silage. Cutting too early when there are still high levels of nitrogen in the grass will cause poor fermentation.

  • <5% – excellent fermentation
  • 5-10% – good fermentation
  • 10-15% – moderate fermentation.
  • 15-20% – poor fermentation.
  • 20% very poor fermentation.

    • ME (MJ/kgDM)

    This is a measure of the energy content of a feed. The ME content of a silage is very much related to the stage of maturity at cutting.

  • Best quality: 11.5.
  • Average: 10.5-11.5.
  • Poor quality: <10.

    • Neutral detergent fibre

    This is a measure of the amount of fibre in a silage. Later-cut silage will have a high NDF. 45-50% is best.

    Lactic acid %

    Lactic acid should be the primary acid in good silage. This acid is stronger than the other acids in silage and therefore is usually responsible for most of the drop in silage pH, which aids preservation. Silage with high levels of lactic acid will have a sweet smell and results coming back between 8-10%, or 65%+ DM, are considered excellent.

    Our farmer in Callan, Co Kilkenny, said it was the best year he ever had farming. February was a wet month, which meant cows were on/off grazing for the month, but by March they were out full-time.

    In total, he only fed 20kg of meal per cow and that was just during the spring. All the rest of their diet was made up of grazed grass. Cows have produced 340kg of milk solids per cow. This year, he grew 13.78t DM/ha of grass, compared to just 10.2t DM/ha in 2013. He commented that one paddock grew 19t DM/ha and that is because it was reseeded last year and is index 4 for P and index 3 for K. He feels it just goes to show if you get fertility right and reseed regularly you will grow more grass.

    Comparing the spring of 2014 and 2013, you can see that grass growth was far ahead this year compared to the same period last year. In April of this year, his farm was growing twice as much grass compared to April 2013.

    Rainfall levels were quite low in July and September of this year, but this did not have an undue effect on this Kilkenny farm and rain came at crucial stages before drought became an issue.

    In Galway, our farmer grew just over 14t DM/ha, which is well above 2013 levels. This year, 91% of the cows calved down after six weeks of a calving period. Just 6.5% were empty after six weeks of breeding. He only fed 350kg/head concentrates this year, which is the lowest amount he ever fed and produced 410kg of milk solids per cow.

    Cows went out to grazing from 10 February and got no silage after going out to grass. Grazing ended on 20 November, with a closing cover of 650kg DM/ha. Three quarters of his land is very dry, while one quarter is heavy land that is only suitable for summer grazing. That one quarter did well this year, however.

    Growth on this Galway farm spiked in early June and mid-August and stayed strong into November. This late growth helped to build covers in August to have a good supply of grass for cows in the autumn.

    This year, the farm grew 22.5% more grass compared with 2013. The farmer’s stocking rate increased from 2.99LU/ha to 3.07LU/ha and with increased grass growth there was no issue feeding these extra cows.

    In Nenagh, Co Tipperary, our farmer had an excellent year in terms of grass growth. Approximately 50% of his land is peaty, which suits a dry year.

    The year began with difficult grazing conditions due to wet weather in January and February, with a total of 249.2mm falling over the two months. Cows didn’t get out until 1 March, whereas usually they would be out grazing from 10 February. After the poor February, the weather changed and cows were out grazing all year with no interruptions.

    In total, he has fed 487kg/head and cows have produced 355kg of milk solids. This year, he has grown 11.38t DM/ha compared to 10.15t DM/ha last year – an increase of 10%. In May of this year, he had super growth rates of on average 70kg DM/ha/day compared with just 55kg DM/ha/day in May 2013. This year, he was able to produce 20% surplus silage from paddocks that became too strong for grazing. The main summer months saw growth rates remain strong with no real dips, but the autumn growth was not as good as 2013 levels. Breeding went very well, with just three empty cows from 58 and two heifers empty out of 22.

    In Co Down, our farmer felt he couldn’t complain about the year, with great prices and a summer to match. He was locked up with TB from September 2013 until June 2014, so he had to carry a lot of extra stock, both young and old. Silage stocks were low at the end of spring, with just 10t left in the pit. He milked 270+ cows through peak lactation and reaped the rewards in the milk returns.

    Spring growth was slow enough until early May. Extra stock led to lower first-cut acreage, which in turn led to small numbers of surplus bales compared to last year. He found a dry month after the second cut led to slow regrowths, which meant he never hit target cover in September. He had to feed bales to slow down rotation. A hustler bale unroller was used to dispense the silage on to the new grass for each day. He found this method had no waste and cows weren’t entering slippy yards. He plans to milk 240 cows next year to keep costs low. He fed 1.1t/head of concentrates this year, but plans to halve that amount next year. This year, he milked 6% more cows and produced 17% more milk.