4 tips to manage the risk of dry silage

Many farms have produced high-quality forage (11.5+ of metabolisable energy) this year and should factor in silage quality to save money by cutting supplementary feeding.

Independent silage consultant Dave Davies of Silage Solutions said that first-cut silages were drier, and with lower fibre, but stressed this doesn’t mean acidosis will be a problem if rations are balanced well.

This week, Trouw Nutrition’s survey of more than 600 first-cut silage samples (see box) found crops were drier, at 35.5% dry matter (DM), and lower in fibre (176.9 fibre index).

But quality energy content was good at an average of 11.4MJ/kg DM.

See also: Exclusive: Investigation casts doubt on NIRS forage analysis

“Most grass continued to grow over the winter, meaning some crops contain a high proportion of older grass which will impact on quality, but overall farmers have made some good feed to act as the foundation for winter diets,” said Liz Homer of Trouw. 

“When clamps are open, care will need to be taken with face management to minimise wastage and heating in the drier feeds.”

Feed more forage

“It all depends on individual farms and what milk price they get and contract they are on, but this year is looking like a year for feeding more forage without having a negative effect on milk production,” said Dr Davies.

He added that, given the milk price and tough year, it would be worthwhile spending money on more detailed forage analyses to cut bought-in feed costs.

Dr Davies gives four areas to watch for farms that have produced low fibre and high DM silages.

1. Low fibre should mean you can challenge cows to eat more forage

  • Lower fibre silages are easier to digest, which means faster passage through the rumen and potential for higher forage intakes, providing forage isn’t replaced with concentrate.
  • Cows can easily eat 1-2kg freshweight a day of additional forage, which is great for both the cows and costs, as in many cases forage is good quality.
  • Calculate how much forage you have as you go through the summer in preparation for the winter period. The biggest questions this year are about quantity rather than quality, as some farms are able to keep milk from forage high at 60-65% or more.
  • The AHDB forage calculator tool is good to gauge forage quantities and estimate feed costs.

2. Aim for 30-32% DM

  • If you’ve made dry silages, you can balance the ration by planning to make a lower DM silage at later cuts.
  • Aim for 30-32% DM. Some farms can manage up to about 35%, but more than this can become hard to ensile and manage in the clamp, due to aerobic spoilage
  • High DM grass blows out of trailers more often, which is wasteful
  • If you are concerned about producing another dry silage, check the DM before you harvest. This is best done in the microwave at 80% of the power. Take samples across the field with sheers. Weigh 100g of forage, then weigh again after drying to calculate the % of DM. See AHDB Calculating dry matter (DM) of samples for more information.
    • An in-field assessment can be given by rolling up grass into a ball and squeezing. If the grass can retain its ball shape but not express juice, then it’s around 28-32% DM.
    • Knowing the standing crop DM enables you to adjust wilting before cutting. In hot, sunny or windy weather, you can quickly end up with 50% DM silages. Avoid this by shortening wilt times. If needed, arrange to cut just before contractors arrive.

3. Invest in more detailed forage testing

  • Conventional near infrared reflectance spectroscopy (NIRS) analyses are not as detailed as doing a nitrate-N analysis  for protein (about £10/sample) or a wet chemistry sugar analysis (about £25/sample).
  • Conducting a nitrate-N analysis is well worth the money, especially this year when dry periods and delayed fertiliser applications have meant that plants have been slow to take up N. This analysis can be done on grass in the field as well as silage in the clamp.
  • If there is a high level of non-protein N for this reason, then a nitrate-N analysis will identify this.
  • This could help avoid over-supplementing rapidly degradable rumen protein, which over-supplies the rumen and can lead to problems with high milk ureas, loose dung, fertility issues and reduced intakes
  • Some high sugar silages will be able to utilise the extra non-protein N, but a nitrate-N analysis will take the guesswork away.
  • Using a wet chemistry sugar analysis to understand the sugar levels in your forage could be very important this year.
  • Sugars will be higher if silage is drier, because less sugar is used up in the preservation process due to the drier silage requiring less acid to preserve the forage

4. Dry silage needs careful management in the clamp

  • Dry silages need to be well compacted, chopped shorter and kept clean to avoid aerobic spoilage at feed-out. This is because there is more air held within the grass at ensiling and easier penetration at the open clamp face.
  • For 35% DM silage, chop to 25mm, For 40% DM silage, chop to 10mm.
  • Feed across the clamp face in three days maximum to reduce chance of spoilage. This could mean using half a shear grab depth, rather than a full one.
  • Don’t leave piles of spoiled silage at the front of the clamp, and remove mouldy grass silage as soon as you see it. If the pile is left in front of the clamp, spores can blow onto the silage in the clamp, increasing the risk of further aerobic spoilage.

Nutrient analysis for early first-cut silages 2020

Nutrients Minimum Average Maximum
Dry matter (%) 19.1 35.5 60.9
Protein (%DM) 8.1 14.6 20.4
D-value (%) 58 71.5 76.1
ME (MJ/kg DM) 9.3 11.4 12.2
Neutral detergent fibre (% DM) 36.2 44.1 58.8
pH 3.5 4.2 5.4
Sugars (% DM) 0.2 3.4 9.7
NH-3 N (ammonia % DM)) 1.1 3.1 9
Volatile fatty acids (g/kg DM) 0.7 15.1 59.5
Lactic acid (g/kg DM) 12 71.2 147.1
Rapidly fermentable carbohydrate (g/kg DM) 135.6 202.6 247.9
Total fermentable carbohydrate (g/kg DM) 362.1 457.5 578.1
Acid load 32.7 49.5 57.4
Fibre index 145.5 176.9 238.1
Dynamic energy (MJ/kg DM) 4.7 6.3 7.4
Source: Trouw Nutrition GB