Reducing grass silage chop length to 2cm (0.78in) could increase dairy cow performance, in some cases, by up to two litres of milk a cow.

And while conventional thinking has always said shorter clamp silage leads to digestive problems, trials have shown shorter particle size increases dry-matter intake and reduces acidosis, says John Allen of Frank Wright. 

“Although longer forage increases salivation and controls rumen pH, mixing it in a ration has shown it to reduce digestibility, as the possibility of producing a uniform mix declines. 

“Cows are known to sort diet, selecting 20-30% fine material before eating longer particles. Longer particles are harder to mix, and poor mixing and ration sorting can lead to cows selecting out higher-starch components.

UK diets

“This means they salivate less, giving lower natural buffering, thus increasing rumen acid production. Acidosis then results, lowering total dry-matter intake, milk yield and overall herd health.

“UK diets are too long. Reducing from 2.5cm to 2cm will give a better mix, less sorting and higher quality, as fine chop in the clamp gets better compaction and fermentation. This coupled with the greater quantity of grass being transported from field to clamp in each trailer makes financial sense with rising fuel costs.

“Contractors should welcome this move, since short cuts will be quicker and more efficient.

“However, a few exceptions to shorter chop length must be noted. Producers making wet silage (less than 25% dry matter), maize silage and whole-crop silage should stay as they are, due to acid loading. 

Type of silage

Individual farms should be clear in their own minds what type of silage they want and should look over the past three years’ production efficiency, says Chris Savery, Dairy Group senior nutritional consultant.

“The benefits of short chop are good consolidation, greater sugar release and fermentation. However, when a lot of concentrates are being fed, short-cut silage could cause an imbalance in rumen pH.

“Individual farms will vary. For instance, when grass is longer but leafy, you can afford to chop at longer length. Too frequently producers are chopping at less than 2cm, which often means chopped straw or hay has to be added to silage to bulk it out, adding more expense.   

“Getting a good crop requires attention to detail in relation to fertiliser application, cutting at the right stage, buck-raking and additives. An inoculant-type additive can be useful, as high populations of lactobacillus can aid fermentation, preserving grass sugars.

“Cutting the crop when there is sufficient grass with a high sugar level is paramount. Planning ahead, being flexible and going with the weather is my advice to make the most from silage.”

Shorter cut

• Better clamp consolidation
• Higher dry matter intake
• Reduced acidosis
• Improved ration mixing