Principle of silage making

The goal of silage making is to conserve and store crop nutrients using lactic acid bacteria to ensure rapid fermentation in air-free conditions and to minimise losses from harvesting until feeding. Whatever the system, the ensiling and storage system's main functions are to exclude air during the ensiling process and to prevent air from entering the silage during storage.
Speed of harvest, moisture content, chop length, silage distribution and compaction can greatly influence the fermentation process and storage losses. Efficient fermentation generally ensures a more palatable and digestible feedstuff. This promotes maximum dry matter consumption by livestock that usually results in improved milk and/or live weight gain performance.
Round Bales


Less dependent on weather conditions
Quality of big bale silage can be as good as other process, and usually better when well managed
Lower aerobic spoilage losses compared to clamp
Easy handling and feeding systems (different silage qualities can be fed when needed)
Tailored dietary solutions, baled silage can easily be mixed with other forages to provide optimal nutritional requirements to different types of stock on farm
Lower dry matter losses during production and storage (<5-10%) than clamp silage
Flexible storage system, bales can be stored in the field or easily transported to any location on the farm
Limited capital investment, low transport and storage cost
Surplus can be sold and create another income for their farm

A convenient option

Baled silage has been proved to be the most cost-effective and versatile option for storing silage, following continuing developments in silage films and baling machinery.

Anyone new to silage production today would look seriously at baled silage: it does not require the building and maintenance of clamps or silos and does not involve significant investment. Similarly, where clamps and silos need repair or upgrading, for example to meet environmental standards, the investment may be considered uneconomical in comparison with switching to using bales, with the convenience they can offer.

A simulation study of two herds of 30 dairy cows conducted by the Swedish University of Agricultural Sciences, compared costs for ensiling in round bales and clamp: bales showed 35% lower costs per kg silage DM fed to the cows.

New research and analysis of costs at IGER confirm that baling is a cost-effective alternative, improving the profitability of dairy herds as well as offering an opportunity for higher quality silage with greater flexibility in management of both grazed swards and silage production.
Comparing costs of bale vs. clamp

Building on the model developed by IGER and Dow in 2004, a Benefit Calculator has now been designed to help farmers predict the costs and net benefits of baled silage in comparison to clamp silage.

The model predicts that for high quality ryegrass silage (ME>11.5) and taking into consideration the dry matter losses from bales and clamp of about 7% and 20% respectively, that producing silage for milking there is a cost saving in favour of wrapped, baled silage of 18$ per tonne of dry matter harvested. This would represent an increased margin of feed costs over milk sales of 4,800$ from 1,000 tonnes of silage prepared and fed as bales compared to feeding clamp silage.

The main factor influencing the reduced costs was silage dry matter loss observed in the two systems with bales varying between 0.2-13% and clamp silage between 18-25%.

Throughout the EU measures have been introduced to control the pollution of watercourses by farm effluent, including liquids from silage clamps, silos or bales.

One of the reasons for the growth in popularity of baled silage is that effluent management requires low capital investment compared to conventional silage. As baled silage is generally made with drier forage, it produces virtually no effluent and no special storage measures are required other than to store bales well away from boreholes and watercourses. However, if the grass ensiled has low dry matter, some effluent is produced and requires management to avoid pollution.

On the other hand, baled silage generates waste film, around 2kg from an eight layer wrap. In some countries this is also subject to legislation concerning disposal or recycling.

Recent studies at the Institute of Grassland and Environmental Research (IGER) in Wales have shown reductions in effluent production from bales wrapped with six layers of film compared to bales wrapped with four layers. Reductions in effluent production can also be achieved by using 750 mm film instead of 500 mm film.

Flexibility and Management System
When using bale silage, fodder is available in smaller units and the farmer has more fodder-management possibilities. Grassland management is easier with baled silage because the time at which the silage is made is not constrained by the need to get it into the clamp or silo.

Additionally, small areas that would be uneconomic for clamp silage or inconvenient for grazing can be used productively for baled silage.

Many practitioners produce bale silage as the work flows can be easily and individually organised. Unlike clamp silage, the production of bale silage is a “one-man technique”. Time needed for coordination and planning as well as the risk of interruptions are both minimal. There is only one machine involved. For clamp silage on the other hand, a number of people and machines are involved and have to work together seamlessly for optimal output. Disruptions during any phase of the process will lead to interruptions to the chain of production.

Once a silage clamp is closed, the fermentation process begins. It cannot be re-opened until required for use. Since few farms have more than one clamp, baled silage provides a viable alternative for second and third cuts, adding flexibility to grassland management and allowing farming strategies to change quickly.

Additional benefits of bale silage adding flexibility to farm and grassland management include:
Less dependence on weather

Compared to other systems of fodder conservation, bale silage production is less dependent on weather conditions. Although the weather has to be good until the bales are wrapped, transportation and storing can be done when the weather is poor.
Feed closer to the animal

Bales prove useful where farms are composed of a number of distant outlying plots. This separation also tends to occur where farms consolidate, which is a process being seen across Europe as a whole. Bringing the grass to a central point can be uneconomic, as is the idea of multiple clamps or silos.
Tailored dietary solutions

Another benefit of baled silage is that it can easily be mixed with other forages, for example in the feed wagon, to achieve the required dietary balance. Analysis services and advice on such matters are increasingly available.

Performance-oriented dairy farmers can label and store bales according to quality — for example according to cuts. This way the best quality silage can be used when the animals most need it, for example with the higher yielding cows at the appropriate period in the milk cycle.
Revenue generation

Depending on the quantity of fodder needed, the purchasing or selling of bales is also an additional advantage. Farmers can sell surplus fodder, as bale silage can be traded easily. Thus, they have created another income for their farm.

Transporting the bales can pose a risk as inappropriate handling can damage the film. A balance must be kept between the benefits of portability and the risk of damage. Care in handling will minimise the risk.

Nutritional Value
Research into the nutritional value of silage indicates that when properly made, with the right materials and machinery, and correctly stored, baled silage can show same or better quality, with less nutrient losses than either silage clamp or silo.

A well-made bale can have the advantage that less air is trapped than in a silage clamp or silo and, following the introduction of bale choppers, the cattle have little trouble tearing out mouthfuls of the baled product, leading to increased fodder intake and milk yields.
Same or better quality

Given the same grass and the same care, bale silage quality will be the same as or better than clamp silage. To compare the quality, the grass needs to be the same cut and given the same care. Poor handling and storage can also affect the quality of silage. Correctly made, baled silage can be the most successfully conserved forage as it has a fibre content and straw length that stimulates the appetite and rumination.
Low nutrient losses

Losses of net energy are inevitable during the fermentation of sugar to lactic acid. However all other losses such as residual respiration, silage effluents, mal-fermentation and aerobic reactions during storage and extraction can be avoided to a great extent.

Research by Per Lingvall at the Swedish University of Agricultural Science in Uppsala revealed that high quality bale silage only loses about 5% of its dry matter content. A prerequisite for this standard is its wrapping with six layers of white film and silage making according to well-established recommendations.

“In Sweden nutrient losses differ between systems,” observes Per Lingvall. In practice, during storage and unloading a tower or a bunker silo, average nutrient losses are calculated at:
10 – 15% in a tower
15 – 20% in a bunker silo
3 – 5% in a tightly wrapped bale with six layers of white high quality stretch film.

Safe and Traceable Feed
Silage offers the benefit of being a home-produced feed. It is clean and natural with complete traceability and a relatively low cost to the farmer. If not correctly stored, whether in clamp, silo or bale, the development of moulds, for example, can pose hazards for humans and for livestock.

However, with correct production and careful handling, there is no reason for baled silage to be a problem. Also, in cases where the wrap of a bale has been damaged, the loss is relatively minor compared with an extensive area of a clamp.

Food safety starts at the beginning of the chain. The hygienic quality of feed is very important for the farmer handling the feed, for the dairy cow and for the milk as a consumer product.

High quality bale silage is a natural and clean material well suited for animal feeding. Traceability is guaranteed in all cases by marking each bale and by documenting the production process — for example in field records.

Cost comparison
University of Wisconsin agricultural engineers reported silage storage costs including capital investment and annual costs at various herd sizes. The analysis included hay silage stored in eight different systems (Table 1). Capital costs included structures and equipment used in filling, storing and emptying the hay silage. No transportation, harvesting, or moving feed to the animals were included. Silos and gravel pads had a life expectancy of 20 years while equipment was assumed to have a 10 years of life expectancy. Annual costs include capital costs, labor, plastic coverings, fuel, and dry matter lost during storage. Forage (hay equivalent basis) was valued at $85 a ton. Tractors were assumed to have other uses besides forage storage and allocated on a proportional basis to handle forage storage. Table 1 summarizes total capital and annual costs per ton of dry matter at two different quantities of stored dry matter (four amounts were calculated in original report).

Capital cost per ton of silage dry matter was highest for new steel oxygen-limiting structures compared to other systems. If refilling occurs with steel oxygen-limiting units (1.5 to 2 times annually), costs will be reduced. Used oxygen limiting and cast in place structures were similar. Silo bags, silage piles, and wrapped bales had the lowest investment. No significant economics of scale occurred above 758 tons of dry matter (other storage amounts evaluated were 1536 and 3072 tons). Capital cost per ton can be important on farms where capital is limiting due to expansion and/or existing debt load.
Fatal Silage Accidents in Wisconsin
Data for 1987-1996
Accident Description Fatalities
Tower Silo –Falls/Asphyxiation/Mold 18
Tower Silo –Unloader 6
Tower Silo –Buried under silage 1
Tower Silo –Sub Total 25

Bunker –Side Collapse/Buried in Silage 4
Bunker –Pinned 1
Bunker –Sub Total 5

Bagged Silage –Sub Total 0


Source: Hoffmann, M., and Richardt, W., 2003: Remarks about ensiling.