Silage Insights - Bale Silage Production
How to prevent reheating and mould development in bale silage

When making bale silage the objective is to produce good silage with the maximum possible value in terms of forage, fermentation and perfect hygienic quality. The most frequent deviations from this objective when producing wilted grass silage in bales are unwanted reheating (massive propagation of yeasts), which is then often followed by the development of moulds (visible fungal mycelia). Both processes are associated with high dry matter and energy losses and with a total loss of mouldy batches. Horses in particular react extremely badly when fed this kind of silage.

The reasons for reheating and the development of mould are very complex and vary considerably depending on seasonal weather conditions as well as the production techniques used. In order to increase the likelihood of preventing the occurrence of both conditions all the potential risk factors have to be minimised. The following measures will help minimise the risk:

Grassland crop composition
Permanent grassland usually consists of desirable high performance grasses such as German rye grass or timothy grass and unwanted varieties such as rough bluegrass or annual bluegrass. The higher the proportion of unwanted grasses (usually in combination with a higher proportion of weeds) the less suitable they are for silage and as a result the risk of mould development also increases.

• Short term measure: if German rye < 40%, weeds > 30%, then use silage additive to prevent mould.
• Medium term measure: post-seeding or new seeding of the sod, permanent grassland mixture: standard GV, couch grass: A1 or A2 then obtain expert advice ¹.

Fertilisation
The amount of mineral-N fertilization used should be adapted to the location and sod. The maximum quantity for the first crop of cattle silage is 80-120 kg/N/ha, for horse silage 60-80 kg/N/ha. Higher amounts than this or increased amounts on inferior sod lead to a deterioration of silage quality and the development of moulds.

Commercial manure (liquid, sullage, dung) should be used on cut surfaces in spring and limited to a maximum of 20 m3 (liquid), 10 m3  (sullage), 150 dt/ha (dung). In dry conditions it is necessary to rake in the residue once spread.

Cutting time and height
The later the cutting period is in the vegetation cycle, the higher the yield. However, there is also a greater risk that among the lower stalks, forage that is already spoilt will be harvested for silage. For this reason, it is important to be flexible about the cutting height, especially when cropping late: 5-8 cm is good for cattle silage, 7-10 cm for horse silage.

Dirt contamination when cropping
Apart from the thickness (or thinness) of the sod the main causes of unwanted forage contamination are molehills and cutting too close, which may cause the formation of butyric acid bacteria (clostridia) or yeasts and moulds to the forage. For this reason, as well as adopting a flexible approach to the cutting height the grassland crops should be raked off several times. Areas that are badly affected by molehills should be excluded from quality silage use. In the medium term efforts should be made to switch between crops and grazing, which may reduce the presence of molehills. Direct abatement is not permitted.

Degree of wilting and time on the ground
The risk of reheating and mould development increases parallel to the time that the forage is on the ground. This is especially true during high humidity and raining periods. In good wilting conditions the time on the ground should be limited to a maximum of 2-3 days with appropriate times for spreading and turning. As such, the ideal degree of wilting for cattle silage is 35-45% and 45-55% for horse silage; in continental climate areas it may even be a maximum 65% dry matter (DM). With the aid of microwave technology the DM content can be determined within about 20 minutes in order to decide if it should be windrowed or compressed.

Instructions for determining dry substance content with a microwave
Necessary equipment: Microwave, scales (accuracy of at least 1g), tumbler, dish or plate, pocket calculator.
- Take representative samples from at least five spots on the field, mix and crush them. Weigh out approx. 50g.
- Place half full tumbler of water in the microwave to avoid risk of fire
- Use max. 200 watts to dry the sample, use five minute drying interval until there are no more changes in weight
- For dry substance readings < 35% it will take about 30 minutes; for approx. 50% dry substance content approx. 15 minutes
- Divide the final weight of the forage by the original wet weight and multiply by a hundred; result: dry mass content in %

Silage additives
There are various DLG approved quality products to combat reheating and mould development, which work well depending on the dry mass content of the silage. Go online to: www.lk-sh.de for a current list of products and prices. Obtain expert advice on usage, choosing products and production techniques.

Bale silage techniques
The silage should be compressed as much as possible so that the desired lactic acid fermentation begins as soon as possible. It is important that bales are loaded evenly either by picking up swaths that match the width of the pick-up or an even loading can be achieved by turning corners. With a dry mass weight <35% the bales can easily become misshapen, which exerts so much strain on the wrapping that water may leak in or mould may develop. The number of layers should be doubled in this case. Pre-stretching should be adjusted to 50-75% for evenly wrapped bales. When placed on the ground, mats should be used to protect the bale wrapping from damage. Wrapping at the storage area is always better than transporting bales, because even with good bale gripping techniques and handling there is a risk of air getting in.

Choice of wrapping and number of layers
The quality of the film influences more than anything how airtight the bale is and therefore how well the risk of mould development can be avoided. Methods that have proven useful are to rely on practical experience or choose DLG approved brands. Unfortunately, their quality may vary from year to year and from one pallet to another. Therefore, whenever new films are used, test wraps should be done to check for tear strength, absence of regeneration, irregularities, holes or gas porosity. When stored on open field the generally accepted number of layers of film for cattle silage is six, for horse silage eight. With given risk factors such as very old, stalky material the number of layers should be increased accordingly.

Ensiling
The ensiling process takes an average of six weeks. The bales should remain sealed for this period. If the bales are opened earlier than this, the forage is likely to spoil sooner, although if used quickly this is not a problem. In special cases a chemical silage additive may stabilise the forage quality so it can be used for feeding. Consult an expert on usage, product selection and production technique.

Bale storage
Bales must be stored in such a way that the foil cannot be damaged. If stored on open land this means making the ground inhospitable for rodents and covering the bales with a protective sheet. Tears in the film should be patched with repair tape as soon as they occur.

Usage frequency
Before being used for feeding make a visual check to ensure the forage can be used for feed (see chart 1). If reheating has occurred or if there are mouldy patches it should be used as quickly as possible otherwise there is a risk of losing the lot. However, when selecting silage it is worth remembering that even batches that look fine may be highly contaminated by bacteria. As such, the points discussed above should be checked for their relevance in the production techniques employed and addressed or improved in future.

Chart 1: Sensory evaluation of grass silage for horses

* for use as feed

1)
GV: grassland-mixture for post-seeding or grain mending
A1: standard acre-grass-mixture for seeding in autumn
A2: standard acre-grass-mixture for seeding in spring

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