Silage management

Grass silage forms the mainstay of winter feeding systems in Northern Ireland with approximately eight million tonnes of this forage made locally each year. Within this section of the RuralNI portal you will find the latest information on the production and feeding of grass silage for the Future Herd and CREAM Herd at Greenmount Campus, CAFRE. The range of topics covered reflect the variety of management systems used to produce and feed conserved forages across Northern Ireland dairy farms. The system chosen will also reflect the specific interests of the farmer.

Silage fodder facts

Fodder Facts provides guidance for livestock producers on winter feeding of cattle and sheep. The aim is to assist producers to plan and manage winter fodder supplies. It will provide guidance on how to assess the quantity of fodder available and estimate the amount required to carry various classes of stock through the winter.

Effluent control using absorbent materialsThe prevention of loss of effluent is an annual challenge when making silage. Silage effluent is not desirable for two main reasons (1) it requires expensive storage facilities because of its corrosive nature and because it is a major source of pollution of watercourses if it escapes into rivers (2) it represents a loss of nutrients during ensilage.

Winter feeding programme

Assessing the fodder requirement and quality

  • be aware of the amount of fodder necessary to carry various classes of stock through the winter - see Table 1
  • calculate the amount of fodder available on the farm - see Table 2. (See Appendix 1 for fodder balance sheet)
  • have the silage analysed to determine its intake characteristics and production potential
Table 1: Estimated monthly feed requirement for various classes of stock
  Silage (tonnes/month) Small hay or straw bales/month
Dairy cows in milk 1.5 17
Dry spring calving suckler cow 1.2 14
200-250 KG store 0.7 7
350-400 KG store 1 10
Ewe 0.15 2*

* Note : assume all stock are fully housed

Table 2: Quantity of roughage in large bales
Roughage Large round bales
(1.3m diameter)
weight (KG)
Equivalent no. of
small rectangular
bales/large bale
Large square bales
weight (kg)
Equivalent no. of
small rectangular bales/large bale
Silage unchopped 450-500 (1) N/A 770 N/a
Silage chopped 600-700 (1) N/A N/A N/A
Wheat straw unchopped (2) 220 15 250 17
Wheat straw chopped (2) 230 15 N/A N/A
Hay unchopped 275 14 400 20

(1) Silage dry matter 22-25 percent
(2) Barley straw produces a denser bale than wheat straw and as a result will weigh more

Assessing the quantity of silage in a clamp.

Measure the volume of silage in cubic metres, that is:

  • length (m) X width (m) X height (m)

The number of tonnes can then be calculated using the conversions in Table 3.

Table 3: Conversion factors to convert silage volume to tonnes of silage
Silage dry matter content
(volume in metres cubed to tonnes of fresh silage)
18 Multiply by 0.81
20 Multiply by 0.77
25 Multiply by 0.68
30 Multiply by 0.60

Worked example

If the silage in a silo measures 28 metres long x 10 metres wide and 2.7 metres deep = 756 metres3.

To convert to fresh weight for a 25percent DM silage then multiply 756 m3 x 0.68 = 514 tonnes of fresh silage.

Tonnage of hay and straw

Count the number of bales and multiply by the weight of each (see Table 2).

Minimum roughage requirement

Ruminants require fibre in their diet for rumination (chewing). Evidence suggests that a diet should contain 25-35 percent neutral detergent fibre (NDF) in the dry matter and that 75 percent of this should come from forage. Table 4 shows the estimated minimum requirements for a dairy cow in milk and a dry suckler cow.

Table 4: Estimated minimum roughage requirements for dairy and suckler cows
  Minimum fresh silage (KG/day) Minimum hay/straw (KG/day)
Dairy cow
(giving 30 litres/day)
(4.5t) (1)
Suckler cow
(550 KG dry cow)


(1) Figures in brackets (Table 4) denote the quantity required per cow over a 180-day winter.

Additional comments

·To meet the animal’s feed requirement high levels of concentrate will need to be fed along with the minimum roughage levels shown in Table 4. Such diets increase the risk of acidosis and laminitis in cattle.

Consult your local DARD Development Adviser if you are considering feeding the minimum amounts of roughage so that a suitably balanced concentrate can be recommended.

General points in relation to feeding cattle and sheep

  • compare the price of compounds/straights/roughages from several different sources
  • consider the use of value for money by-products as straights (see Table 5) to replace a shortfall in roughage
  • analysis of roughages should be carried out before any rations are formulated
  • producers involved in home mixing must be aware of the need to register with DARD. This will include farmers who buy in complementary feeds (such as mineral feedingstuff or protein concentrates) containing additives and mix them with their own material

Relative feed value of straights

Where a fodder shortage exists for stock you intend overwintering, extra feed will have to be purchased. Table 5 shows the relative values of various straights when fed. 

Table 5: Relative feed values of straights compared with barley/soya
  Value (£) Effective ME Protein percentage
Barley 85 11.4 9.5
Wheat 85 11.4 11
Maize (high silage diet) 95 13.2 8
Maize (high concentrate diet) 105 13.2 8
Maize gluten (growing cattle) 91 10.9 18
Maize gluten (finishing cattle) 82 10.9 18
Maize germ meal 86 10.5-12.5 10
Molasses 57 8 4
Molassed sugar beet pulp 79 10.6 9
Sunflower 84 8 27
Soya 130 11.6 46
Rapeseed 113 10.8 36
Cottonseed 97 9.5 30
Maize distillers 106 11.6 26
Fishmeal 153 12.2 62
Copra 98 11.5 20

(Assume barley @ £85/tonne and soya meal @ £130/tonne) 


  • values calculated using DARD relative feed value programme
  • barley at £85/t excludes a £10/t rolling/milling charge
  • prices of barley/soya prevailing at mid October 1998. By comparison feeds such as maize gluten, maize distillers, copra and rapeseed are good value for money however they are more variable in composition

Rationing fodder

  • mark silo walls with each month’s ration of silage for the stock on the farm. One bay of a silo 35 ft (9.1m) wide, 15ft 9 (4.8m) long, and filled to a settled depth of 6ft (1.8m) holds 53 tonnes of silage at 25 percent DM
  • where stock are fed restricted quantities of roughage ensure adequate feed space is available (for example, weanling 500mm, suckler cow 750mm). This may mean reducing stock numbers in a pen or providing additional feed space such as a ring feeder
Table 6: Standards used when formulating rations for the various enterprises
  Good silage Average silage Hay Straw Beef concentrate Dairy concentrate
DM percentage 25 20 85 86 87 87
CP (percent DM) 15.8 14 8.5 4 17.2 20.7
ME (MJ/KG DM) 11.5 10.8 8.6 6.5 11.8 13
Cost (3/t fresh) 14 11 75 55 120 120

Wholecrop wheat silage

Is your crop ready? - producing wholecrop wheat silage

Dr. Aidan Cushnahan, Milk Technologist, Greenmount Campus, College of Agriculture, Food and Rural Enterprise

Wholecrop wheat silage is being used increasingly by dairy farmers as a complementary forage to grass silage, especially as part of a total mixed ration in complete diet feeding systems. The successful preservation of wholecrop wheat silage depends on making an accurate assessment of dry matter content prior to harvesting and paying attention to detail when harvesting and filling the clamp. The following article will deal with these factors in more detail.

Preserving wholecrop wheat

There are two distinct systems for ensiling wholecrop wheat:
Fermented wholecrop - harvested at 35 - 45 percent dry matter. The majority of ensiled wheat crops in Northern Ireland are preserved using this method.

Urea treated wholecrop - harvested at 50 - 60 percent dry matter. The urea is converted to ammonia in the silo which inhibits the action of spoilage organisms.

When to cut?

The feeding value of wholecrop wheat is highly dependent on achieving the optimum balance between the increasing starch level in the ripening grain and the decreasing digestibility of the straw. Decisions on when to cut are therefore critical and should be based on assessments of dry matter content. It is important to monitor dry matter content on a regular basis as this gives an indication of the nutritive value and quality of the crop.

The following guidelines should be observed for fermented and urea treated wholecrop wheat:

Fermented wholecrop should be harvested at 35 - 45 percent dry matter (growth stages 71 - 85). The crop colour at this stage is changing from green to yellow and the texture of the grains has changed from watery to cheesy (soft Cheddar).

Urea treated wholecrop should be harvested at 50 - 60 percent dry matter (growth stages 85 - 92). Crops at this stage should be surface dry and the grains will be difficult to indent with a thumbnail (hard Cheddar). It is important not to apply urea to crops with a dry matter of less than 50 %. If this occurs, a foul smelling unstable product is likely to be produced.


The preferred method of harvesting is using a precision chop harvester fitted with a combine harvester header (which may require some adaptation) so as to minimise grain losses through shredding. Cutting height can vary between 7.5 and 15 cm (3 and 6 inches) depending on the quality of the crop. Chop lengths of approximately 25 mm (1 inch) can aid consolidation in the clamp. Ensure that the trailer door and sides are boarded or sheeted to minimise grain loss.

There are a number of additives available which can be applied to fermented wholecrops at harvesting. A number of these products have been shown to improve the stability of the resultant silage upon exposure to air. The cost of these additives can vary considerably, therefore careful selection is very important to ensure that any additive used is cost effective.

Urea should not be applied to crops which have been undersown with grass as this will interfere with the fermentation. In situations where urea is being added, thorough mixing of the urea into the crop is essential for a successful preservation. This is best achieved by applying urea through the crop stream on the harvester. However there may be practical difficulties with this method due to the application rates involved (40 KG/ tonne dry matter). Other methods of application include using a fertiliser spreader on tipped loads and mixing well with the harvested material before ensiling.

Any form of urea other than feed grade urea should be tested for purity before use.

It is also vitally important to ensure uniform distribution of urea throughout the crop since a lump of pure urea consumed by a ruminant is toxic and can cause death.


Provided the dry matter content of the harvested crop is within the target ranges outlined, whole crop wheat will not produce any effluent. Under such conditions a silo is not required for storage - hard standing is adequate.

When clamping fermented whole crop wheat, a narrow clamp is considered advantageous as this reduces spoilage due to secondary fermentation which takes place during feeding out. The crop should be filled quickly in thin layers, consolidating well as it is filled. The clamp should be double sheeted and sealed effectively with the top sheet being weighted down with tyres or bales. If tyres are being used on an outside clamp it may be advisable to net the clamp to avoid potential damage by birds.
Similar measures are used to store urea treated wholecrop wheat, provided both crop and urea have been mixed adequately. The crop only requires moderate consolidation and the clamp should be thoroughly sealed to prevent ammonia escaping.


Wholecrop wheat can be successfully preserved by regularly monitoring crop dry matter content prior to harvesting and paying attention to detail when harvesting the crop and filling the silo. Particular care should be taken if the crop is being treated with urea to achieve an even distribution of urea through the crop. Further information on producing wholecrop wheat silage can be obtained by contacting your local Farm Development Division Adviser.

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