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LAMMA 2021

LAMMA 2021

Bad silage is costing farmers a lot of money

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What is the true cost of bad silage?

Wesley Habershon is a dairy consultant and nutritionist with the Farm Consultancy Group, he was commissioned by Yara to look at the cost of making bad silage. Mr Habershon estimates this could be as much as £32,000 for a 120-cow herd producing 9,000 litres per cow per annum.


Table 1 illustrates two current grass silage analysis and their key characteristics. The poor grass silage was cut three weeks after the good silage and suffered from some inadequate management and weather issues. While much importance is given to the top three characteristics in the table, as much importance should be given to the others given their role in influencing palatability, fermentation, energy and protein values.


Palatability is key to dry matter intake. Dry matter, ammonia (NH3-N), volatile fatty acids (VFAs), ash and sugar all influence how attracted a cow is to a silage. Ammonia, for instance, reduces intake, as do VFAs which include the unpalatable butyric and acetic acids. Table 1 demonstrates how a good silage has lower levels of ammonia, ash and VFAs. The objective of good silage-making is to achieve a stable forage (pH 3.8-4.2), transformation of sugars into lactic acid (70g/kg+), digestible fibre (NDF 40-45% DM), 75maximise utilisable protein available to the cow and, most importantly, to maximise energy values (11ME+). The issue with the poor forage is not just assigned to the energy and protein values but how much the cow wants to eat, how much she can effectively digest and produce in yield and milk constituents.

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Late applications


High ammonia results can be the result of late fertiliser applications (ammonia reduces the fall in pH), insufficient wilt, inadequate fermentation (pH 4.4+) and secondary fermentation. Protein is particularly susceptible to degradation from inadequate pH (pH 4.4+) and forms ammonia, amines and amides.


This issue occurred in the poor grass silage meaning more protein is needed to supplement the ration and this was achieved through more soya/rape meal and some feed grade urea. Poor silages need more concentrate, fats and improved palatability and even then, cows will never perform as well as with a well digested high energy grass silage. I have applied both these forages to a typical farm situation based on 9,000-litre cows. The forage element was based on 25% maize silage poorer silage needs a palatability driver to encourage appetite and I have chosen 1.75kg of molasses (see Table 2).


Fermentable starch from caustic wheat and bypass protein from the soya/rape blend are also required to boost intake, while fat is needed to boost the energy density to sufficient levels. As a result, a 30-litre cow requires 10.85kg of concentrate to achieve production, whereas a cow fed the better silage requires 7.54kg. If we assumed for simplicity that these cows were housed all-year-round the additional feed cost would translate into £32,000, with a potential additional increase in £13,000 of improved milk yield if cows were fed a better grass silage (see Table 3).

Feed efficiency


The feed efficiency translated from 0.35kg/litre to 0.24kg/litre between both forages with a purchased feed cost saving of 3.19ppl. If we incorporated the forage cost there would be a 2.43ppl difference between the diets (12.13ppl for the poor forage and 9.7ppl for the better forage), this difference is less than the purchased feed cost because we are gaining more milk from forage and so must feed more forage per cow. The forage figures above were based on market costs, correct nutrient application and good farming practice both a poor and high-quality grass silage should cost in the region of £27.50/tonne, albeit a poorer forage maybe slightly cheaper due to some shortcuts. Significant figures include £247/hectare land rent, £9.53/tonne fertiliser and application cost and £1.67/t attributed to the cost of instalment of a silage clamp over 50 years.


We would expect a fouryear perennial grass ley to produce on average of 56t/ha grass silage across the year with at least 22t/ha of quality first cut grass silage taken before the second week of May. However, such figures are based on good fertiliser management, mowing at optimum sugars, sufficient grass wilting, significant compaction and attention to detail. In summary, cutting earlier, managing nutrient requirements, investing in new leys and attention to detail are key to regularly achieving high-quality forage. As the financials indicate the financial benefit over a 9,000-litre, 120- cow milking herd can mean a £32,000 saving and the potential for a further £13,000 in increased milk performance. Cutting earlier will also boost yield per hectare and reduce the lignin (no nutritional benefit) content. Weather will always impact our decisions, however, even in the wet years good silage-makers always make better forages and this is due to timing, application and detail.

Table 1

Poor silage Good silage

Dry matter (%)

32 28
Crude protein (%) 11 14.5
ME (MJ/kg) 10 11.5
pH 5.5 4
NH3-N (%) 5.5 1.2
Sugar (%) 8 4
Ash (%) 10.5 3.8
NDF (%) 512 440
Volatile fatty acids (g/kg) 50 11
Lactic acid (g/kg) 15 75


Table 2

Poor silage Kg Good silage Kg
Good grass silage 34.5
Poor grass silage 28.5
Maize silage 9.5 11.5
Molasses 1.75
Caustic wheat 2 2.4
Feed grade urea 0.03
UFAC Dynalac 0.4
Protein blend* 4 2.4
Dairy HDF 18% 2.2 2.4


Table 3

Key financials Poor silage Good silage
Concentrated use/litre 0.35kg 0.24kg
Purchase feed cost/litre 8.48ppl 5.29ppl
Annual feed cost £169,352 £136,979
Average ration cost £3.62 £3.12


To improve grass silage quality we should aim for:


  • <250mg/kg nitrogen levels before cutting
  • Mow from early afternoon (3pm optimum sugar levels)
  • Spread crop wide to aid wilt and reduce plant respiration
  • 24-hour field wilt (but at least seven hours+) jFrequent cutting reduces lignin build-up and boosts energy values
  • Avoid soil contact
  • 30% target dry matter at harvest
  • 4-8cm target chop length
  • pH 3.8-4.2 jConsider additive application as an integral part of the process, for example, to improve digestibility
  • Consolidate, consolidate, consolidate
  • Clean silage pits before to avoid contamination and avoid soil on silage trailer wheels
  • Sheet rapidly and cover when made over multiple days
  • Use non-porous cling film to help reduce aerobic spoilage
  • Manage silage face with a shear grab or equivalent after sufficient fermentation (six weeks+)
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