1. Silage making is an art, just like making good wine. Like anything worth doing, it isn't easy but it is worthwhile.

2. It's an accepted fact that well fermented, rapidly fermented , high moisture feed retains more nutrients than any other method of harvesting and storing crops.

3. By understanding the basics of the fermentation process, using good management practices, you can aid nature in achieving a rapid, effective fermentation which preserves more of the valuable nutrients in your forage crops.

4. By learning how to consistently make excellent silage, you can lead to a greater yield of meat and milk per acre.

5. A good fermentation improves the palatability of a feed. The fermentation process in the pit is very similar to the digestive process in the first stomach of cattle. Well fermented silage's are a natural feed for cattle. Nutritionally, it's like putting your animals on green feed all year round.

MICROBIOLOGY OF SILAGE PRESERVATION :-    Ensilage is the transformation of plant material into a succulent preserved fodder. The preserving acid is produced by bacteria which grow and multiply on the cut crop.

Ensilage cannot add to the feeding value of the original crop. Only minor losses occur when things go well; serious losses and unpleasant side effects take place when things go badly.

The transformation can take many paths. The main reason for the large amount of poor quality silage made every year is the mistaken belief that silage making is 'a natural process'. The crop is cut, packed into bales and left to nature, the elements and good fortune to convert it into the succulent and nutritious foodstuff required.

Silage is man made. It is up to the farmer to ensure that some natural processes take place whilst other equally natural processes are suppressed. This means subjecting the cut crop to carefully controlled, wholly artificial conditions so that wasteful respiration and undesirable bacteria are kept in check and beneficial pickling fermentation increased to a maximum.

This desirable state is maintained until the silage is fed to the stock.

If one or more of the basic rules are ignored due to ignorance or oversight, substandard silage is obtained.

The various changes which take place in the transformation from cut crop to silage are outlined in these notes.

STAGE 1:- The Cut Crop

The cut crop is made up of the following components:-

1. The chopped plant material.

2. Moisture within and between the cut stems and leaves. (Refer to Stage 2)

3. Air trapped between the cut stems and leaves. (Refer to Stage 3)

4. Bacteria which produce acetic-acid. (Refer to Stage 3)

5. Bacteria which produces lactic acid. (Refer to Stage 4)

6. Plant sap slowly oozing for the cut surfaces of the crop. (Refer to Stage 4)

7. Bacteria which produce butyric acid. (Refer to Stage 5)

STAGE 2: Correct Moisture Content   

MOISTURE WITHIN AND BETWEEN THE CUT STEMS AND LEAVES. The moisture content of freshly cut grass is about 80 percent. It varies form 83 percent in young, leafy material to 77 percent at the flowering stage.

In addition to the moisture contained within the plants, the cut crop may be wet with rain or dew.

Ensiling plant material which contains too much water is dangerous for two reasons, both of which result in dry matter loss:

1. Desirable fermentation is less likely in sodden green stuff, as the butyric acid bacteria relish such conditions. Bad fermentation means protein loss.

2. A large amount of seepage arises from wet material in the silo, and this carries away valuable nutrients as well as creating a disposal problem.

To avoid trouble, material to be ensiled should be free from surface moisture. Crops with a low dry matter content, such as young grass, lucerne and clover, will produce better silage if allowed to wilt for a few hours before ensiling.

Wilting is a technique which must be used with care. A crop containing less than 70 percent moisture runs the risk of overheating with a serious drop in carbohydrates and digestible protein as the result.

STAGE 3: Removal of all the Entrapped Air :-   

AIR TRAPPED BETWEEN THE CUT STEMS AND LEAVES.

Respiration by the plant cells continues as long as air is present. As a result sugars and the poly saccharides which produce them are broken down and carbon dioxide and water are produced. The outward sign of this destruction of carbohydrates is a rise in temperature of the ensiled crop. The more rapid and greater the rise in temperature, the greater is the loss of nutrients.

In addition, there is a loss in the value of the protein content because high temperatures increase the degree of indigestibility. The damaging effect by heat becomes much more serious when the danger point of 120 deg.F, is exceeded and this easily happens if an appreciable quantity of air is present, as when a steamy un-chopped crop is insufficiently consolidated.

It used to be thought that a temperature of 95 deg F to 102 deg F, was essential to ensure good fermentation. This meant leaving a certain amount of air within the cut crop to promote respiration and the resulting 'heating up'.

It is now known that equally good or better silage can be produced at low temperatures; that is below, 80deg.F. 'Cold Fermentation' has at last been recognised and accepted in Europe.

The argument for air in the silage has disappeared. Air is a menace for a number of reasons:-

It results in a loss of carbohydrates and total dry matter.

It reduces the digestibility of protein.

It makes it more difficult for the beneficial bacteria to thrive, as air destroys the sugars which the lactic acid bacteria requires.

It greatly reduces the value and amount of the silage if it is present in sufficient amount to promote serious over heating.

It increases the amount of seepage. One of the products of respiration is water.

Obviously, this stage in the silage making process is an undesirable one and should be reduced to a minimum. This calls for excluding air from the silage, and these are the factors which help to do this:

Use of young material containing at least 70 percent moisture.

Chopping or laceration. Especially important if the crop is dry and mature, and for crops such as maize and kale.

Very rapid ensiling.

Consolidation. The amount required will vary with the, crop, stage of growth, amount ensiled and moisture content. Young leafy crops require little consolidation, as they pack down on their own accord. On the other hand, dry and mature green stuff will need heavy compaction.

Application of an efficient seal.

In addition, at this stage:-

BACTERIA WHICH PRODUCE ACETIC ACID.

The first bacteria to become active in the silage are the coliform types. They produce small quantities of acetic acid. This acid plays little part in the silage story, and is regarded as of little importance.

STAGE 4: Production of the Preserving Acid    

BACTERIA WHICH PRODUCE LACTIC ACID.

Successful fermentation, and that means successful silage making, depends on the growth of bacteria which produce lactic acid. The organisms involved are the Lactobacilli, and to a lesser extent the Streptococci.

It is obvious that this stage will not occur if conditions are completely unsuitable for the growing of these bacteria. Even if conditions are ideal, the Lactobacilli will get away to a very slow start if only a few of them were present in the cut crop.

Normally they are abundant, and it is up to the farmer to make sure that conditions for rapid growth are provided.

These bacteria spring to life once the air has disappeared or has reached a very low level. Air removal is one prerequisite for rapid growth; the presence of sugars is another. Mature grass, maize and the other 'easy' silage crops contain adequate sugars for this purpose. The 'difficult' crops, such as young grass, clovers and lucerne are short of sugars. Further more, these protein rich but sugar deficient crops tend to have a high moisture content, which is another feature disliked by the Lactobacilli. For this reason an additive is essential to make sure the 'difficult' crops pass successfully through Stage 4.

It takes about 20 days for the cut crop to pass through Stages 3 and 4. At the end of this time there will be 1 to 2 percent lactic acid in the cut crop (now properly styled as 'silage') if all has gone well. The pH of the silage will be in the region of 4.0 and at this degree of acidity the lactic acid bacteria are inactive.

The spoiling bacteria which break down protein and produce butyric acid are also unable to grow at this acidity, and so the silage is preserved as an acidified succulent fodder. This desirable state is maintained as long as the lactic acid remains undiluted. If a proper seal or roof is not provided, the rain water can drain through the good silage and wash away the preserving acid. The putrefying bacteria will then come to life and the farmer will be confronted with evil smelling silage on opening his silage.

PLANT SAP SLOWLY OOZING FROM THE CUT SURFACES OF THE CROP.

It is obvious from the above paragraph that the faster the plant sap containing sugars can ooze out to where the bacteria are, the faster these acid producing bacteria can grow and multiply.

When a crop is chopped into small pieces, there are many more cut surfaces form which the sap can ooze. When it is bruised and lacerated, the escape of the sap is even quicker. For this reason, chopping or laceration helps fermentation.

STAGE 5:-   Protein Breakdown and the Production of Butyric Acid by Spoiling Bacteria

BACTERIA WHICH PRODUCE BUTYRIC ACID.

This bacteria should not be allowed to develop. Their activity is a sign that Stage 4 has not been a success because Stage 5 cannot take place if all has gone well during the lactic acid production and conservation period.

As with other bacteria, rapid colonisation of the silage by these spoiling types depends on the organisms being present in sufficient numbers at the outset and on conditions being suitable for their growth and multiplication.

The first line of defense against the butyric acid bacteria is to make sure that as few as possible enter the silage. The bacteria involved belong to the Clostridia group, and these occur most commonly in soil. Avoid picking up soil with the crop and do not use dirty leaves as a source of silage.

DON'TS  

1. Don't get dirt in the feed.

2. Don't allow holes or damage to the Polythene covering.

3. Don't place bales in a poorly drained area or under trees.

4. Don't allow dogs, cats and other animals to get on the Polythene sheet.

5. Don't ensile feed to dry or mature.

6. Don't put excessively wet forage in the bales.

DO'S  

1. Do protect the storage area from livestock.

2. Do inspect bales on a regular basis and mend holes with sealing tape.

3. Do place bales on a well drained, hard surface.

4. Do have your feed tested to be able to mix and balance your ration.

5. Do ensile your crop at proper moisture and maturity.

6. Do number and date bales for easy testing and recall of material ensiled.

7. Do place bales in accessible area for easy feed removal.

INFORMATION FROM DEPARTMENT OF AGRICULTURE OF N.S.W. FACT SHEET WRITTEN BY MR. B.R. McGUFFICKE DISTRICT AGRONOMIST AT INVERELL   

SILAGE :- What is silage?

Silage is edible plant material stored in oxygen free (anaerobic) conditions and preserved by the acids produced by the fermentation of plant sugars.

Ensiled material will last almost indefinitely if it is kept in oxygen free conditions.

The main advantages of silage over hay are that it is cheaper and easier to handle mechanically when large quantities are involved and it is not as easily damaged by bad weather.

For successful silage all air must be expelled by compacting the plant material. The exclusion of oxygen favours the lactic acid producing bacteria which ferment sugars (soluble carbohydrates) and produce lactic acid.

Failure to expel air will allow the development of moulds and other micro-organisms and result in excessive heating and silage spoiling.

Moisture and wilting   What is silage?

Ensiling a wet crop (>80% moisture) will result in the loss of valuable nutrients in silage effluent and encourage unwanted (clostridial) bacteria. Wilting will assist fermentation where the moisture content of the crop is high.

Successful lactic acid fermentation will depend on enough plant sugars being in the ensiled crop. Plant sugars are usually low in legumes and young grasses. Wilting or using silage additives, or both, help overcome these problems.

Young pasture crops commonly contains only 10 to 20 percent dry matter. Ideally the dry matter content for silage should be 25 to 35 percent. Leaving material to wilt in the paddock after cutting is the simplest way to increase dry matter content. Wilting is less critical when precision - chopped forage is ensiled or where an acid additive is used. Over wilting can cause problems as air penetrates more easily than in unwilted material. Additives are not necessary unless the forage is less than 20 percent dry matter and the soluble carbohydrate content is low.

Cutting Stage What is silage?

The stage of plant development influences plant digestibility and therefore its value as a livestock feed. While plants remain in the vegetative stage their digestibility and forage values are high. As the plant starts to mature and the flower emerges digestibility falls rapidly

Cutting time is a compromise between highest yield and highest quality. Optimum time of cut will vary to cater for the nutrient requirements of different types of stock. Where maximum quality is the aim it will be necessary to sacrifice some quantity and cut earlier to achieve higher digestibility.

I will use forage sorghum as an example of quality and quantity variation with cutting time.

Forage Sorghum   What is silage?

Hybrid forage sorghums have a high dry matter yield and rapid growth rate. They are able to regenerate rapidly after Cutting or grazing. The most effective way to manage forage sorghums is to repeatedly Cut or graze them when growth or regrowth reaches about 1 metre.. Up to 3 or 4 cuts can be made in a season. Forage sorghum requires large quantities of nitrogen to produce good yields and adequate quality fodder. If phosphorous levels are low in the soil phosphate fertilizer may also be required.

The feed value of forage sorghums declines rapidly as they mature. The quality decrease results from the increase in indigestible fibre in the stems of the plant. The following table shows a typical decline in quality with increasing age at Trangie.

To achieve a DM digestibility greater than 60% it is necessary to graze or harvest forage sorghums at a crop height of about 1 metre. This is usually about 2 months after sowing. A wilted silage (Jumbo) was harvested 56 days after sowing for a research study. The crop was 1.38 metres tall and yielded 6.9t/ha of dry matter. It was wilted for 24 hours to about 32% DM. The silage produced had a pH of 4.1 and a DM digestibility of 63% for cattle.

All sorghums have the potential to release HCN. Young plants have the highest HCN levels but plants growing under severe stress can also have high levels of HCN. Ensiling reduces HCN more than hay making. The HCN is lost in the gaseous form during the ensiling process.

Sorghum often contains inadequate sodium for cattle and sulphur can also be deficient. Contact livestock officers for further information.

If sorghum is direct cut for silage and not wilted the best stage for maximum quality is early flowering. Winter cereals such as oats would be cut at the full flowering stage and lucerne at the early flowering stage. The use of wilting or additives would allow all of these plants to be cut at an earlier stage with an increase in forage quality.

B.R. McGufficke
District Agronomist
INVERELL
27 May 1992

The nutritive value of wilted silage probably needs little emphasising to the farmer. The storage of silage in bales has come a long way since the early 1980's from the practice of big plastic bags and then to plastic stretch film. This tightly wrapped film excludes air from the bales so speedy fermentation takes place. The flexibility and convenience of this silage system is a huge advantage.

Contractors and farmers alike can benefit from harvesting early feed surplus when the weather is often unfavorable for other forms of storage. Other major advantages include lower field losses and better quality feed than hay, also valuable ground moisture is not lost trying to dry crops.

Scientific research has established that certain ideal conditions for feed storage and processing will maximize the feed value, one can preserve virtually all of that value until the crop is fed to livestock. This ideal is achievable if you place the crop in an oxygen-free environment at a moisture level in the 60 - 70 percent range. Once ensiled, a fermentation process begins - the chopped pieces respire for a short time thereby raising the temperature to a level between 26 to 38 degrees, where the lactic acid producing bacteria thrive. After approximately three weeks of fermentation, the ratio of acid to alkaline drops to about 4.0, indicating a stabilized silage which will remain constant until fed.

Temperatures above 38 degrees create a sweet tobacco-like, caramelised silage which may be palatable, but has lost much of its nutrient value. Temperatures above 38 degrees will result when too much oxygen is present and excessive oxidation of the plant occurs.

Hay

To bale a legume or grass crop, the material must be dried to a moisture of 10 to 15 percent. Consequently, there is a field loss of 25 percent or more, whether the hay is baled into small or large square bales or round bales. Additionally, dry matter storage losses range from 5 percent for hay bales.

Silage

With silage stacks or bunkers, the field losses of either maize silage or legume and grass silage's is minimized by harvesting at high moisture. The harvested material is then dumped into what is usually a three-sided concrete bunker or built into a stack and packed by rolling heavy equipment over the material.. The material is then covered with plastic protection. However, the exposure of silage to oxygen in storage will result 20 to 40 percent dry matter losses.

The conventional technology represented by such storage systems as baling, stacking or bunkers does not achieve the ideal storage conditions of ensiling the harvested crop at a high moisture in an oxygen-free environment. Consequently, significant losses will occur at every stage of the harvesting and storage process. These losses are field loss, storage loss, and feed value loss.

Field Loss

Field loss, caused by leaf and ear drop or by downed stalks, occurs when a crop loses it moisture before chopping. Field loss can be reduced to a minimum of 4 percent if maize silage is harvested at 65 to 70 percent moisture. These losses increase to 16 percent when the moisture level falls below 60 percent, the field loss of legume or grass goes from a low of 2 percent at 70 percent moisture, to greater then 13 percent at 55 percent moisture. Pasture crops should be weed free and cut at 10-20% seed head then wilted to 70% moisture.

Storage Losses

Exposure to oxygen, resulting in oxidation and improper fermentation, causes the visible deterioration of the stored product. It becomes very clear in the graph below that to minimize field and storage losses has huge benefits to the farmer which more than offsets the cost of baling and wrapping.

Feed Value Loss

Feed value loss is the invisible loss resulting from insufficient fermentation, resulting in a drop in nutritive value beyond the loss of dry matter. Additionally, consumption loss can occur when stock refuse to eat because the feed has become unpalatable in storage. These losses occur because the conventional methods cannot achieve effective fermentation or significant reductions in storage losses.

Summary

With ever-rising production costs, farmers must seek new ways to improve their productivity and profit through good management . Good management calls for maintaining peak nutritional levels and eliminating the costly losses normally associated with conventional storage methods.