Silage quality: Top tips on how to make better forages

That was the main topic of conversation at a recent forage webinar during which Ken Stroud of Volac, encouraged farmers not to cut the crop too low or to over-wilt, and to spend more time checking the height of a mower and tedder, if used, in the field.

Ken Stroud says the biggest mistake farmers are making is overwilting

“Over-wilting is one of the biggest mistakes farmers can make,” he said. “You should look to achieve a wilt within a matter of hours rather than days.”

Mr Stroud added: “I would advise farmers to start mowing at 10am if there is a good strong breeze and harvest at 26% dry matter in the first day rather than throw it out for hours to achieve a 30% dry matter on the second day, when much of the quality will have been lost.

“The maximum wilting period should be 24 hours,” he said.

Cutting height

Furthermore, he stressed that regardless of feed supplies available, farmers should not shave fields or cut lower than the last leaf node.

“Cutting height is so important. Leave a reasonable amount of stubble away from the soil – no less than four inches – and it's the same with tedding. The tedder should comb the grass, not scrape it. If you go too low you risk increased soil contamination and that creates more problems.”

Climate change is also creating more challenges when farmers struggle to get slurry onto the fields which as a result can mean waste is spread between cuts – which in turn increases the risk of contamination.

Mr Stroud added that while many farmers rely on a few good days of dry, sunny weather to make the best forages, there is a lot more to producing a palatable, nutritious feed than its ME, D Value and protein level.

“I see huge variances in the analysis of silage on a yearly basis, but I also consistently see a large number of farmers who have very little understanding of the analysis, what it means and how to use it.

“Farmers have to know how to produce better quality forages and the technology is there to help them improve but there is a slow uptake. The ones who do understand analysis learn from it when they have records of cutting dates, tedding and harvesting conditions alongside slurry and fertiliser applications and dates. These farmers consistently produce high quality 12ME silages.”

However, to understand an analysis, he said that farmers first have to provide a sample the correct way which involves taking a representative sample from the pit, putting it in a double wrapped plastic bag making sure all the air is out of it, and posting it as soon as possible. It should also be clearly labelled.

“Keep samples in a coolbag with freezer blocks around it or put it in the fridge until it has been posted. Ideally, it should be posted the same day it has been collected and at the start of the week so it’s not waiting over the weekend.”

Commenting on the basic references in an individual silage analysis, he said the main ones – dry matter (DM), protein (CP) and intake potential – all vary depending on the crop, weather and the fermentation.

Understanding a silage analysis can help farmers understand how to improve next year's crop

Dry matter (DM)

“DM can vary from 20-38%, but the target for clamped grass is around 30% and higher for maize and wholecrop. It’s also generally higher for baled silage for beef and sheep farmers although its not unusual to see it lower these days,” he pointed out.

“Protein values can be very variable in grass and range from 11-20% depending on the amounts of fertiliser/slurry applied and the variety of grasses. Grasses with a high clover content and herbal leys tend to have higher protein levels.”

However, intake potential, he said can vary from lab to lab.

In turn, he highlighted NDF or neutral detergent fibre, which he said is a figure determining plant maturity and the rate of digestion in the rumen. High levels of NDF (more than 55) are associated with low D Value silages and low intake levels. Ideally, livestock producers should be aiming for silages with an NDF of less than 50, while dairy farmers should be aiming for less than 45 for high-yielding cows and multi-cut systems.

Commenting on sugars and water-soluble carbohydrates, Mr Stroud said they vary from 0-6% in very high dry matter silages with low levels desirable as long as they have been utilised to create lactic acid and not the undesirable acetic or butyric acid. He added that high residual levels of sugars can improve palatability but also increase the risk of aerobic spoilage, whereas high levels of butyric acid (more than 9g/kg of DM) can be harmful and result in reduced performance/milk yields. The use of a proven inoculant such as Ecosyl will, however, ensure more sugar is converted to lactic acid to improve fermentation.

Ammonia

Ammonia or NH3% as total N, is an indicator of how much protein has been broken down completely during ensiling. High levels above 10 point to poor fermentation and would have benefitted from a more efficient wilt and the use of a proven inoculant. The aim, he said, should be for below 5% TN.

A figure for lactic acid is also shown on the analysis which can range from 80-160kg/DM with the most optimum being 80-120kg. Mr Stroud added that the ratio of lactic acid to VFAs should be an absolute minimum of 3:1 and he would like to see 5:1 or more to see the best fermentation, which again can be achieved with a proven inoculant.

Farmers can learn from the volatile fatty acid figure on the analysis too as high levels indicate a poor fermentation. Instead, he said the aim should be to produce as low a figure as possible and certainly below 20. VFA, which is a measure of the undesirable acids, butyric and acetic, can be reduced by considering a lighter crop, and a 24-hour maximum wilt.

“VFAs have been increasing over the years which is due to climate change and the pressure of getting slurry out on fields, but again, they can be reduced by spending five minutes in the field – not in the steading on concrete – checking that the mower/tedder aren’t set too low in the field.

Ideally, a pH of 3.8-4.2, he said is acceptable, although they are generally higher in high dry matter silages of more than 35%. The lower the pH the greater the acidity – and the less chance there is of secondary (butyric) fermentation occurring.

Ash content can also point to poor fermentation with a high figure indicative of soil contamination.

“Uncontaminated grass would see ash content levels of 5-8% so levels greater than 9% indicate significant soil contamination leading to poorer fermentation. If the ash content is persistently high, greater attention to cutting and tedding height will reduce the risk of contamination.”