Feedstuffs

Feedstuffs for cows can be divided into roughage and concentrates. The difference between the two categories is not always obvious, but feedstuffs that contain a large percentage of fibre are normally called roughage.

Roughage .

High quality roughage is the feedstuff that is most fundamental for a high milk yield. From a nutritional point of view, the cow can be fed only grain and concentrates, but roughage influences many other functions, including rumination. Roughage is important in dairy feeding for at least four different reasons:

1. It is a quality source of nutrients; 2. It is essential for the rumen microbes; 3. It is essential for rumination; and 4. It regulates the rumen pH.

Long fibre particles (> 4 cm) are essential for the rumen microbes. The bacteria attach to the particles, which have to stay in the rumen long enough for the bacteria to multiply. If the fibre particles stay for a shorter time than the bacteria generation interval, the bacteria population will dissappear.

It is very difficult to draw general conclusions regarding nutrient content in roughage. It all depends on the type of the roughage and its maturity when cut. As the total harvest increases over the season, the nutritional value - as energy and protein - decreases (see picture below *).

Development of total harvest, and content of energy and protein in herbage.

Milk yield from Alfalfa of different maturity

Milk yield when feeding alfalfa hay and 20% grain. The quality of the hay varies according to maturity.

American scientists (Kawas, et al.) examined how milk yield was affected by different stages of alfalfa maturity. In the trial, 20% of grain was fed together with alfalfa hay of different maturity. By feeding pre-bloomed, instead of latebloomed, alfalfa hay milk yield increased by 35% (see picture below).

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Conserve forage

Hay
Making hay is a drying process where moisture content is reduced to below 15%. Mature crops are easier to make into hay than immature crops, and losses are lower, but they are also of lower feeding value. Making hay is a very weather sensitive process. Some farmers use drying fans so that they can bring in the crop from the field with a higher moisture content (approximately 40%). This reduces field losses and makes the process less weather sensitive.

Silage Making silage is a fermentation process where micro-organisms use available sugar to form lactic acids. Since the early 1950s in most developed countries the total quantity of forage preserved as silage has increased steadily. The advantages of harvesting forage as silage rather than hay include:

Ensilage

•  Less dependence on weather conditions
  
• More nutrients are preserved, primarily due to reduced feed loss
  
•  Increased mechanisation of harvesting, storing and feeding
  
• A wider selection of crops able to be harvested as silage
  
• Silage is better suited as an ingredient in a TMR.

A successful silage programme requires consideration of a wide variety of factors, from agronomic management to harvest, storage and feeding practices.

First priority - stop oxidation
When freshly cut grass is stacked in a heap its temperature rises. This is due to the heat produced by chemical reactions that take place within the crop. Once this heating process starts, it can rapidly speed up, mainly because the warm air produced by these reactions rises out of the heap, thereby drawing in fresh air (similar to a draught through a domestic fire). As a result, the sugars in the crop can be quickly burnt up. The first priority in silage making is, therefore, to stop the oxidation of sugars by preventing fresh air getting into the cut crop. This is achieved by compressing and consolidating the crop through rolling. After rolling, the surface of the crop should be covered with plastic sheeting to prevent air moving through the silage. As hot air is prevented from escaping, so no more fresh air is brought in.

Next priority - stop chemical and microbial activity
Even if the flow of fresh oxygen is stopped, grass in the heap is still completely unstable because of other chemical reactions that continue. For example, protein in the crop begins to break down, producing amino acids and ammonia. Yet more seriously, bacteria and moulds that are present naturally on the grass when it is cut can rapidly multiply and begin to decompose the crop into a putrefying and nasty-smelling mass. Both chemical breakdown and undesirable microbial activity must therefore be stopped as quickly as possible, and this can be achieved either by sterilising the crop or by making it acidic.

pH-drop
Undesirable bacteria and moulds that are present in the cut crop are sensitive to acid, and are inactivated by low pH levels. Under controlled conditions, most green crops undergo a natural fermentation process, where lactobacilli, a group of micro-organisms, use available sugar to form lactic acid.

The initial reduction in pH values from normal 6.8 down to 5.0, which is necessary for some control over the undesirable micro-organisms, does not require the production of a lot of lactic acid. Yet the lactobacilli will only produce this acid when the crop is anaerobic, hence the vital importance of preventing air getting into the silo. Lactic fermentation also gets under way much more rapidly with chopped, rather than with long, crops.

Even with consolidation and careful sealing, where anaerobic conditions are established and an initial pH drop is achieved, a further reduction in pH is necessary. This reduction, in many cases to below 4.0, is needed to completely halt protein breakdown and undesirable microbial activity, and thereby ensure safe, long-term storage. However, the rate at which the pH value falls also begins to slow down, since less sugar is available for fermentation, and progressively more acid is needed to bring about every additional pH 0.1 unit decrease . pH is expressed on a logarithmic scale, so it takes ten times as much acid to reduce the pH of a crop from 5.8 to 4.8, as it does from 6.8 down to 5.8. This emphasises the importance of a sufficient sugar supply in grass to produce the required amount of acid.

The pH drop in untreated silage and silage treated with inculants.

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Additives
Several different types of additives can be used to improve the silage process. The most common are bacterial inoculants with enzymes, organic acids and sugars.

Bacterial inoculants reinforce the natural process of fermentation.

Fermentation is initiated by bacteria, particularly the lactobacilli that are naturally present in the crop. However, some crops do not provide enough bacteria, or the right types of bacteria, to initiate the lactic fermentation. For many years, researchers examined the possibility of adding extra bacteria to the crop.

Bacterial inculants with enzymes.

Until recently, this was of only limited success because not enough was known about the optimum types of bacteria. New research has isolated active strains of a number of bacteria, and as a result there has been a surge of interest in the development of bacterial inoculants.

To be effective, bacterial inoculants still require the crop to contain fermentable sugar. There is thus interest in using specific enzymes with the ability to break down some of the crop.s complex sugar to simple sugar, which can then be fermented by the bacteria. Most of today.s products contain both inoculants and enzymes.

A practical advantage of using bacterial inoculants is their safety. Unlike acids, they are unharmful, both for the people using them and for machinery. Research has also shown a higher level of voluntary intake of silage, and lower dry matter loss, compared to silage made without additives.

Acids
When applied uniformly throughout the crop, acids cause an immediate fall in pH and complete cessation in both chemical and microbial action. Lactic acid, however, still needs to be produced within the crop in order to enable stable, long-term storing. The most commonly used acid is formic acid, though propionic acid is also used, as it is claimed to reduce surface moulding when the silo is open.

The major disadvantage with acids is that the operator has to handle large quantities of dangerous liquid. They are also corrosive on the machinery used and strong effluent has to be collected and spread on the field.

Sugar
The most common reason for poorly-preserved silage is that the crop contains insufficient water-soluble carbohydrate (sugar), which is needed to produce the required amount of lactic acid. The idea behind adding sugar to the crop, most often molasses, is to reinforce its natural sugar content. However, the necessary volume is generally between 5.15 litres per ton of fresh crop, which is more than with most alternative additives, and this demands substantial organisation if harvesting is not to be slowed down.

It is not necessary to use an additive to make good silage. But an additive can reduce the risk of problems, especially when silage is made from problem crops which are very wet, immature, cut late in the season or contain a low sugar content. Many additives can also improve the nutritional value of the silage, both by increasing the amount of silage that livestock can eat, and by changing its chemical composition compared to silage made without any additives.

Harvesting Most annual and perennial crops can be used for silage. The harvest time is of vital importance for the feed value of the silage. Harvesting should be carried out at the optimum combination of yield and stage of growth (see picture above marked with *). Failure to cut forage crops at the right stage is widespread, and the temptation to wait a few days for a little more bulk can seriously reduce crop quality.

Wet crops are difficult to preserve. High moisture levels mean that more acid has to be produced to preserve the silage. Wilting the crop has many advantages: reduce the weight of the crop that has to be carted from the field and loaded into the silo; greatly improve the ensilage process and the feeding value of the silage; and reduce effluent loss from the silo. Grass should be cut, if possible, using precision chopping, because this breaks the cell walls of the crop and makes the sugars more available for fermentation by lactobacilli. Chopping also improves grass consolidation. During every stage of harvesting and silo loading, any possible risk of contamination should be avoided.

Storage system
The silage pit should be as clean as possible to avoid contamination of the grass. Before the season starts, always clean the bunker or tower with a highpressure cleaner. The life span of the bunker can be extended by protecting the walls with plastic surface protection. This will also make cleaning easier.

Four types of storage system for silage are commonly used:
- Bunker - large capacity. Can be filled and emptied with conventional farm equipment;
- Tower silos - greater mechanisation during filling and feedout, and less area for construction;
- Round bales - lower capital investment, good flexibility; and
- Stack - low-cost alternative, but high DM loss during storage.

Feeding out
Letting in air can lead to aerobic deterioration and moulding. The exposure of the silage face should be kept to a minimum and it should be moved back sufficiently quickly. As a guide, the face should be moved back 10 cm a day in cold weather, and 30 cm in warm weather. Disturbance of the face should be kept to a minimum through the use of a block cutter or shear grab.

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Summary .

• Making silage is a fermentation process where micro-organisms ferment sugar into lactic acid.
  
• The grass should be cut at the optimum combination of yield and stag growth.
  
•  Wilting improves the fermentation process.
  
• The available amount of sugar is critical for production of the required amount of acid.
  
• Regardless of the type of storage system, it is important that anaerobic conditions are achieved.
  
• Additives can reinforce the fermentation process and reduce the risk of bad silage. They can also improve the nutritional value of the feed.
  

The feeding value of the forage depends on many things, including maturity, day length, latitude, temperature, soil, fertilizer, particle size, weather conditions, and how well the feeds are preserved. Many dairy cows are fed annual crops like corn silage, sorghum silage, cereal silage and annual rye grass. Other crops like millets, sudan grass, sunflowers and rape are also of importance in certain parts of the world.

Pasture .

Pasture is utilised in many different ways around the world. Some farmers use grazing as the sole source of nutrition, others use grazing only for exercise. To make the most of grass growth, calving is often seasonally timed so that most cows are in peak production at the time of greatest grass growth. During spring growth, some of the grass can be conserved as hay or silage and be fed during seasons when there is less grass growth.

Milk from grass

Milk produced from grazing without buffer feeding or concentrates is generally associated with farming in New Zealand, but this method is also common in many other countries. It is a form of milk production system that is regarded as low input. Production per hectare is more important than production per cow. The production level can vary between 2 000 and 5 500 kg per lactation.

Milk from grass and concentrates

During the grazing period, cows are supplemented with concentrates, usually in the parlour or in the tied stall. Depending on the equipment, this can be done according to flat rate or yield. The production level ranges between 3 500 and 7 500 kg per lactation. With irrigated grass that has been grazed at the optimal stage of maturity it is possible to reach an even higher production level.

Milk from grass, roughage and concentrates

As the genetic potential of cows improves, grazed grass is not nutritionally dense enough to provide the cow with sufficient nutrition. Many farmers buffer feed with other roughages. This can be done by feeding the cows buffer feed along with grass, or by keeping the cows indoors at night (or day). The buffer can be a TMR or roughage and concentrates fed separately.

Buffer feed is also a good indicator of how well the grass is managed. If there is a shortage of grass, the cows will eat more buffer feed. The system of buffer feeding is less affected by drought or extremely wet or cold weather conditions. Production levels range from 5 000 kg to approximately 14 000 kg per lactation.

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Grazing methods

We can distinguish three forms of grazing management:
1. Set stocking, where a herd or a group of cows remain on the field over a long period;
2. Rotational or paddock grazing, where there is close sub-division and the cows are moved between different paddocks; and
3. Fold grazing, where the cows are given a ration of grass behind an electrified wire which can be quickly moved to a new position, usually at least once a day.

A more controlled form of grazing provides the farmer with better tools to manage the feed supply to cows. The rate of grass growth will vary through the season and where there is surplus grass some paddocks can be used for silage or hay.

Green chop

Green chop is used as an alternative to pasture. The crop is cut in the field and brought to the cow. Suitable crops are corn, grass, whole crop grain and legumes. Green chop has both advantages and disadvantages.

Advantages:
- Better control of the animal.s feed intake; and
- Lower feed demand due to less animal activity.

Disadvantages:
- The crop has to be harvested each day; and
- Fields can be damaged in rainy weather.

Concentrates .

Concentrates are purchased compound feeds, straights and grain. Many byproducts are also called concentrates, but it is preferable to define concentrates as non-cellulosic or low-cellulosic carbohydrates. By-products with a lot of fibre, such as sugar beet pulp and brewers grain, do not have the same effect in the rumen as concentrates. They should therefore not be called concentrates. It is important to remember that roots and potatoes have the same characteristics as starchy feeds. These ferment rapidly in the rumen.

In general, concentrate consumption should not exceed 65% of the total dry matter intake. If a cow does not get enough fibre, the result can be disturbances in the digestion system.

Cereal grain

Examples of grain are corn, barley, oats, wheat, triticale and rye. The characteristics of grain are:
- High energy content, primarily starch;
- Relatively low protein content; and
- Generally low fat content.

There are quite significant nutritional variations between the different grains. Corn has less protein and fibre, but more energy than other grains. Wheat and barley have a higher energy contents than oats. Oats contain more fibre, which slows down digestion, and they also have a high fat content. All grains are palatable except for rye. Because of its poor palatability, rye should not exceed 20% of the ration.s dry matter content. Large ratios of wheat and triticale may also affect palatability negatively.

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Field beans and peas

Field beans, lupins and peas are good ruminant feeds as they contain a high level of energy and protein. Legumes contain plenty of quickly degradable protein and therefore must be balanced with other feeds.

By-products from grain

The by-products from grain usually contain little starch but most of the protein and fibre fractions from the original grain. Energy content will vary depending on the processing method. Products such as wheat feed, wheat bran, oat feed, maize gluten feed, maize gluten meal and maize gluten germ meal are commonly used around the world to feed ruminants.

Oilseeds and oilseed residues

Many concentrates are produced from oilseeds, such as soya bean, cotton seed, groundnut, sunflower seed and rapeseed. Of these, soya bean is most common. Palm kernal, coconut, linseed, sesame and safflower may also be used, but they are less interesting in this context. The oil is usually pressed or extracted from the seed and the residues contain the protein and carbohydrate fractions.

By-products from the sugar industry

Molasses and sugar beet pulp are excellent feeds for ruminants. Beet pulp is the residue that remains when sugar has been extracted from sugar beets. Beet pulp has a high content of digestible fibre, which slowly degrades in the rumen. Ergo beet pulp does not have the characteristics of a concentrate. Molasses are quickly degraded in the rumen and are also a very palatable feed. However, molasses also have a high level of potassium, which can sometimes cause problems.

By-products from brewing and distilling

All over the world, brewers grain is a commonly used by-product. It is low in starch and contains high levels of protein. Similar products are maize, wheat or malt draff from distilleries.

Protein balance

To produce a well-balanced ration, it is important to mix feeds so that the ratio of degradable and undegradable proteins is optimal for the cow: (of crude protein) 60.78% degradable protein and 22.40% undegradable protein depending on production level.

Feedstuffs with high levels of degradable proteins:	Feedstuffs with high level of undegradable proteins:
- Urea (a non-protein nitrogen); - Legume silage; - Grass silage; - Lupins.	- Meat and bone meal; - Fish meal; - Maize gluten meal; - Heat-treated soya bean meal.

Buying concentrates

The farmer can buy concentrates as straights, blends or as manufactured concentrates. What the farmer chooses depends on the farm situation and the type of feeding system used on the farm. Manufactured concentrates can be made up of many different raw materials so as to suit the farmer’s needs.

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