Guidelines for Making Good Quality Baled Silage

[Irish Farmers Journal Article, May 2000]

 Padraig O’Kiely(1), Dermot Forristal(2) & J.J Lenehan(1)

1Teagasc, Grange Research Centre, Dunsany, Co. Meath

2Teagasc, Oak Park Research Centre, Carlo

Importance
Baled silage is now made on most farms in Ireland. It is the main system of providing winter fodder on the majority of small-sized farms. Although larger-sized farms usually produce precision-chop silage they are likely to also make baled silage with surplus grass from grazing paddocks or for some or all of their second-cut. Finally, meadows intended for hay production are often salvaged as baled silage if weather conditions in June and July don’t permit adequate field drying of grass. It is therefore not surprising that the quality of grass conserved in baled silage covers a huge range. This has been confirmed over several years when samples of bales from large numbers of farms were analysed at Grange.

Characteristics
The average dry matter (DM) content of baled silage on Irish farms is about 32% DM with a corresponding mean pH of 4.8. This contrasts with corresponding values of 22% DM and pH 4.0 for conventional silage. Clearly, baled silage is generally receiving an adequate wilt. Wilting is obviously an important accepted part of baled silage systems which have sufficient flexibility built into them to make it feasible.

Principles
The principles of making baled silage are precisely the same as those governing conventional pit silage. For a variety of practical and economic reasons these principles will be fulfilled using a different set of practices to conventional silage. Nevertheless, the critical importance of (1) rapidly achieving air-free conditions and maintaining them rigorously through to feedout, and (2) of achieving an adequate reduction in silage pH (modified by the extent of wilting), are as essential with baled silage as with conventional silage. Similarly, within baled silage, these two fundamental principles must be fully satisfied for moderately or extremely wilted grass, for long or chopped grass, for large or small bales and for round or rectangular bales.

Problem
Most aspects of the feeding value of baled silage can be directly related to the characteristics of the grass when it was baled. However, the one major exception to this is the occurrence of mould on baled silage which is entirely related to what happens after the bales are wrapped in plastic film. Mould is a much bigger problem with baled silage than with conventional silage. It is also substantially preventable.

Quality
Baled silage with a high feeding value will be highly digestible and well preserved, just as with conventional pit silage. Thus, leafy grass with its higher digestibility and therefore higher feeding value than stemmy grass is necessary if baled silage is to have a high feeding value. Excellent preservation as already mentioned requires the conditions that prevent mould growth and gets the pH to decrease sufficiently.

Plan
It is important if the investment a farmer makes in baled silage is to be adequately repaid that the making of baled silage is pre-planned rather than being an impromptu or salvage operation. In addition, some degree of flexibility is necessary in the system, particularly to ensure satisfactory wilting. With this in mind, the following are a set of guidelines for producing good quality baled silage.

Guidelines
1. Grow a quality crop. If silage of really high feed value is consistently required (i.e. 75+% DMD) then a strong case for a ryegrass sward can be made. If on the other hand the baled silage is for dry spring-calving beef suckler cows or for store cattle managed within extensive production systems then the case for reseeding may not be compelling. Fertilisers are important to secure an adequate yield. To facilitate the production of a quality crop, fertiliser and/or slurry should be applied early, evenly and at the correct rates to ensure both the maximum yield response and the minimum negative effects on quality.

2. Harvest leafy, digestible grass. Grass crops need to be harvested when seed-heads are emerging from the grass plants if baled silage of superior feed value is to be produced. Well preserved, palatable baled silage can be made from stemmy grass, but its feeding value will not be high. This latter type of baled silage may be perfectly adequate for dry spring-calving beef suckler cows whose nutrient requirements during winter are modest, but it will be quite inadequate for lactating cows or finishing cattle unless supplemented with significant quantities of extra concentrates.

3. Wilt mown grass quickly to 25 to 30% DM. Whereas wilting is often not feasible, and sometimes not desirable, with conventional silage, it is an important part of baled silage systems. It facilitates good preservation, prevents effluent production, reduces the number of bales (and therefore the cost) per acre and makes the bales lighter and therefore potentially easier to handle and store. Research at Grange has shown that even where bales are stacked 3 tiers high during storage, that effluent was not produced with grass wilted to above 25% DM.

The aim when wilting should be that the mown crop would not spend more than one night on the ground. This requires good drying conditions and exposure of a significant amount of the crop to sunshine. Obviously, the former demands some flexibility in harvesting date to ensure the crop is not mown until suitable weather is forecast. In addition, when suitable weather arrives, the crop should be mown after the dew has dried off as dew will dry faster from a standing compared to a mown crop. Wilting grass is dried mainly by sunshine, so the greater the extent to which mown grass is spread out in thin layers the faster the rate of wilting. Consequently, spreading grass to give it full ground cover (i.e. tedding) immediately after mowing results in the fastest rate of wilting, whereas mowing and combining two wide swaths results in the slowest wilting rate, while other treatments are at various stages in between. This is clearly shown in Table 1 – note the significant benefit of the simple technique of opening the gates wide behind the mower conditioner and leaving a wide rather than a narrow swath. With light crops in good drying conditions, overwilting should be avoided if feasible.

Table 1. The effect of swath treatment on grass drying rates, expressed as % DM in a 12 t/ac crop.

"double" swath mower conditioner

Day 1, 9 am: 16.0
Day 1, 2 pm: 18.1
Day 1, 5 pm: 16.8
Day 2, 2 pm: 17.9

mower conditioner - "standard"(1)

Day 1, 9 am: 16.0
Day 1, 2 pm: 19.5
Day 1, 5 pm: 20.6
Day 2, 2 pm: 22.4

mower conditioner - "wide"(2)

Day 1, 9 am: 16.0
Day 1, 2 pm: 22.2
Day 1, 5 pm: 24.5
Day 2, 2 pm: 30.4

spreading/tedding

Day 1, 9 am: 16.0
Day 1, 2 pm: 24.2
Day 1, 5 pm: 28.9
Day 2, 2 pm: 38.7

(1)2.4 m cut mower producing a 1.2 m wide swath
(2)2.4 m cut mower producing a 1.6 m wide swath
Source: Oak Park Research Centre

4. Conventional additives are not required if a quick wilt to 30% DM is achieved. This is shown in Table 2 by the results of a recent experiment at Grange. Every effort should be made to achieve an adequate wilt and avoid any need to apply conventional additives. If wilting is not possible, very stemmy crops or those with 3% or more sugars should also preserve properly without additives. However, sometimes unwilted difficult-to-ensile crops have to be ensiled, as can happen in September or October, and these crops should have high rates of acid or sugar based preservatives sprayed across the swath before pick-up. It is difficult to achieve intimate mixing of grass with additive, but important that as good a job as possible be done.

Table 2. Effects of different types of additives applied to wilted baled silage.

dry matter (%)

No additive: 31
Acid(1): 29
Molasses: 28
Inoculant(2): 28

dmd (%)

No additive: 73
Acid(1): 74
Molasses: 76
Inoculant(2): 74

crude protein (% dm)

No additive: 15
Acid(1): 16
Molasses: 15
Inoculant(2): 16

ph

No additive: 4.3
Acid(1): 4.2
Molasses: 4.3
Inoculant(2): 4.3

lactic acid (% dm)

No additive: 7
Acid(1): 6
Molasses: 7
Inoculant(2): 8

acetic (% dm)

No additive: 2
Acid(1): 2
Molasses: 3
Inoculant(2): 3

ammonia-n (% n)

No additive: 11
Acid(1): 10
Molasses: 11
Inoculant(2): 11

mould at opening

No additive: -
Acid(1): -
Molasses: -
Inoculant(2): -

Heating at feedout (°C)

No additive: 11
Acid(1): 14
Molasses: 13
Inoculant(2): 15

(1)Formic or sulphuric based; (2)average of 3 brands
Source: Grange Research Centre

5. Produce dense, well-shaped bales. This results in heavier but fewer bales per acre, thereby reducing baling and wrapping costs. In addition, well-shaped bales are easier to wrap properly and to handle without causing damage. Some issues worth high-lighting are:

a. Swath presentation

• A wide, even 'box-shaped' swath is easily picked up by the baler and will help ensure good bale formation.
  
• Standard width baler pick-ups will handle 1.1 - 1.2 m wide swaths. Wide baler pick-ups will handle 1.1 - 1.4 m wide swaths.
  
• Swath width can be varied by setting the swath formers on mower conditioners or tedders/rakes.
  
• 'Hay-bob' type machines need careful setting (forward speed, p.t.o. speed, swath doors) to avoid producing very uneven swaths.
  
• Mower conditioners inherently produce even, well-shaped swaths for baling.
  

b. Baler operation

• The baler density setting should be set to its maximum allowable position.
  
• Excessive forward speed should be avoided, particularly where heavy uneven swaths are being baled.
  
• Good operator technique will ensure even filling of the bale chamber and well-shaped bales.
  
• Some conflict exists between farmers' requirement and contractors' need for output.

c. Chopper balers

• 'Fixed-knife' choppers use a rotor to pull the grass through a fixed bank of knives. From 11 to 14 knives are normally used, giving a nominal chop length of 85 to 110 mm. Some balers can be fitted with up to 23 knives.
  
• Increases in bale density are variable, depending on grass type, dry matter and sward presentation, but are normally in the region of about 10% over unchopped bales.
  
• Chopped bales are easier to distribute at feeding but the chop length is much longer than conventional precision or double-chop silage.
  
• Costing estimates suggest a chopper baler would typically cost 30p+/bale extra to operate.

6. Wrap bales carefully and adequately. The purpose of wrapping bales in polythene film is to achieve and maintain air-free conditions.

Successful wrapping requires the provision of dense, well-shaped bales. These are easier to wrap properly, to handle without causing damage and to store successfully.

Film used for wrapping bales is usually in 750 mm wide rolls, and is stretched on the wrapper to a length 70% greater than its original length. Conventional film should not be stretched more than this. When wrapped in four layers of film, the thickness of polythene on a silage bale is 70 m m compared to 250 m m for a double-sheeted silage clamp. Since each tonne of baled silage typically has 6 to 8 times the surface area in contact with polythene compared to clamp silage, it is clearly important that the film is of good quality and that it is applied properly.

Bale wrappers are geared to apply film whereby each layer overlaps the underlying layer by 50%. In Ireland, four layers of film are typically used, although in countries such as Sweden six layers are the norm. The number of revolutions of the wrapper turntable needed to ensure a nominal covering by 4 layers of film (750 mm) on a regular, well-shaped bale is about 16 turns. This can increase where irregular-shaped bales are involved.

Experiments at both Grange and Oak Park have shown that a minimum of 4 layers of conventionally applied standard stretch film as required to conserve baled silage adequately. Where good management practice prevails, the benefits accruing from progressing to 6 layers of film are small (Table 3).

Farmers should watch their bales being wrapped, and be sure that not less than 4 layers are being applied. This can be checked by counting the number of wrapper turntable revolutions needed for the bale to be completely covered once with plastic. This gives two layers of film (remember the 50% overlap) on almost all of the bale it is necessary to give one additional turntable turn to ensure two layers throughout. Then double this figure to give the number of turns required for four layers. Farmers should also count the number of bales wrapped per roll of film. The wrapper should have a good bale-drop table to minimise damage to the film as the wrapped bale is ejected onto the ground.

Plastic film should be purchased from reputable sources only, and wrapping should be done in accordance with the wrapper and plastic manufacturers recommendations.

Table 3. Importance of having adequate plastic film on bales. Measurements are shown for 2, 4 and 6 layers of stretch film.

rotted surface area (%)

2: 73.1
4: 5.2
6: 0.1

rotted depth (cm)

2: 48.0
4: 3.1
6: 0.6

dry matter (%)

2: 26.8
4: 29.0
6: 30.0

ph

2: 6.2
4: 4.6
6: 4.4

dmd %

2: 66.6
4: 71.1
6: 72.0

lactic acid (% dm)

2: 4.0
4: 6.1
6: 6.5

ammonia-n (% n)

2: 17.9
4: 12.5
6: 11.9

Source: Grange Research Centre

7. Handle bales gently. Gentle handling of bales before and after wrapping is essential in order to maintain the shape of the bales and the integrity of the seal provided by the plastic film.

Ideally bring the bales to their site of storage and wrap them there. This can help significantly reduce the opportunity for damage to the plastic film. However, even these unwrapped bales need to be handled gently as rough handling can mis-shape the bales and make them more difficult to wrap perfectly. Transporting unwrapped bales on a spike can readily mis-shape the bales.

Bales should be wrapped as quickly as possible after baling, and any handling of wrapped bales should be within a day of wrapping. An extended delay can allow some bales settle thereby making it more difficult to lift them without causing damage to the plastic film. Furthermore, the plastic stretch film on bales may withstand transport better immediately after wrapping compared to some days later. It is extremely easy to damage the integrity of the plastic seal during transport and, once any harm is done, it is difficult to fully remedy. The importance of gentle handling cannot be over-emphasised. Hence the attractiveness of wrapping bales at the site of final storage. Only specialised bale handling equipment (not spikes), properly operated, should be used to move wrapped bales.

8. Storage. Remove wrapped bales from the field quickly to avoid bird damage. Ongoing research within Teagasc indicates that considerable amounts of damage can occur due to birds (mainly rooks) during the relatively short interval between wrapping in the field and removal to storage. Store wrapped bales on a level, smooth, hard surface with good access so the bales can be conveniently retrieved for feeding. Select a clear (i.e. uncluttered) site that is not too exposed. Unwilted bales should be stored on the ground (on curved side or flat end) whereas successfully wilted bales can be stored 2 or 3 high (on curved side only) if suitable handling equipment is available. Unwilted bales can produce effluent, which would need to be collected and used properly. Ideally bales should be covered (top and sides) in fine-mesh netting to prevent bird and cat damage during storage. Spacers such as tyres should be used to keep the netting out from the bales. The site should be fenced off and steps taken to reduce the risk of rodents. Inspect the bales frequently and repair damage immediately.

9. Feeding

• Big bales can be fed at any stage after wrapping.
  
• Aim to have big bales consumed within 2 days of unwrapping.
  
• Physically remove and discard mouldy bales or parts of bales and do not offer to livestock. Wear an appropriate face mask etc. when handling this mouldy material.

Use a feeding system that permits ad libitum intake, but prevents silage wastage. Circular feeders are perfectly successful in many circumstances. Some problems have occured with feeding bales in slatted floor accommodation. Pen configuration or size may allow whole bales to be presented to animals at the feed face. Using a chopper baler will reduce the risk of cattle pulling silage onto slats and thus into slurry tanks. Bale splitters or unrollers can effectively be used to present the material to animals along the feed face although the former system may require some manual forking of the material. Bale chopper/feeders are available which can give good distribution and chopping of the silage but they are relatively expensive and have a high power requirement.

10. Collect the plastic wrap after removal from the bale, and dispose of it in an environmentally benign manner. The Farm Relief Services currently operate a collection and safe disposal scheme.

Phil Rogers MRCVS, Lucan, Dublin, Ireland​
Fax: 353-46-26154 Tel: 353-46-26740 (Lab)
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