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Animal feed resources information system
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Wood

IMPORTANT INFORMATION: This datasheet is pending revision and updating; its contents are currently derived from FAO's Animal Feed Resources Information System (1991-2002) and from Bo Göhl's Tropical Feeds (1976-1982).

Datasheet

Description
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Common names 

Wood, wood by-products, untreated wood, treated wood

Species 
Processes 

The most promising treatments for making wood more digestible are the following:

Ball milling

This method reduces the wood to microparticles. As particle size decreases, more cellulose is exposed. Carbohydrate digestibility in ball-milled wood approaches that of feed grain (70-80%).

Chemical treatments

These include treatment in aqueous solutions of alkali and vapour-phase treatment with sulphur dioxide. Red oak has been made 55% digestible by chemical treatment. After steeping in a solution of 15% sodium hydroxide, a poplar species with 5% dry matter digestibility in vitro had a digestibility of 50%. Alkali-treated aspen and birch sawdust have constituted up to 30% of ruminant rations with good results.

Steam

In some cases steaming has been a very effective method of increasing digestibility. Steamed aspen wood with a dry matter digestibility of 48% was used successfully as a substitute for hay in sheep rations.

Muka

The needles of conifers and the leaves of deciduous trees can be made suitable for animal feeds with little processing. Basically all that is required is heating at 210 C for a few minutes to drive off moisture and unpalatable essential oils, followed by milling. The major development of this process has taken place in the USSR, where about 100,000 tons of the product, called Muka, are fed to animals each year. Muka is somewhat similar to lucerne, being rich in cellulose, carotene and minerals and containing one half to two thirds as much protein. It is fed as a supplement to poultry, cattle, milking cows and pigs at 5-8% levels. The major impetus to the development of Muka in the USSR appears to have been the large-scale production of essential oils with Muka as a by-product.

Fungal degradation of lignin

This process is based on the ability of white-rot fungi to utilize lignin with minimum degradation of cellulose and hemicellulose. The product is a high cellulose-hemicellulose fibre which is a potential roughage for ruminants. Fungal degradation is slow compared to steaming or chemical treatment as it requires several weeks, but this is not necessarily a serious drawback. The process has not yet been developed for practical use, but the research in this area is intensive.

Nutritional aspects
Nutritional attributes 

Wood contains a high percentage of potentially digestible carbohydrates, but when fed in the form of untreated sawdust or chips it is largely indigestible, even by ruminants. The structural components of wood - lignin, cellulose and hemicellulose - form a close physical and chemical complex called lignocellulose. Lignin gives plants strength and rigidity. The content of lignin varies from about 2% in immature forages to about 15% in mature forages, whereas in wood the percentage is somewhat higher. It is completely indigestible and also lowers the digestibility of cellulose and hemicellulose by acting as a physical barrier to cellulose-splitting enzymes. Hemicellulose consists of digestible polysaccharides constructed mainly or 5-carbon sugars. The sugar xylose is the commonest component of hemicellulose in forages. The digestibility of hemicellulose varies from 45-90%, depending on the sugars it is composed of. Cellulose is usually the most abundant polysaccharide of the lignocellulose complex and consists of 6-carbon sugar glucose. Pure cellulose is fully digestible by ruminants. The lignocellulose complex accounts for most of the gross energy in common forages and wood. The mechanism by which lignin affects digestibility is complex. Rye straw has nearly the same lignin content as birchwood, but rye straw is far more digestible. Hence the lignin content in itself is not a reliable yardstick for measuring digestibility. Wood species differ widely in lignin content, but as a rule the wood of conifers contains more lignin than deciduous or broad-leaf trees.
Numerous feeding trials and laboratory experiments have shown that the nutrients in untreated wood are essentially unavailable to farm animals with the exception of a few less lignified hardwood species. The new concept of feeding cattle on high-grain rations has increased the possibility of using wood residues like sawdust and chips as the roughage component. Experiments have shown that sawdust is an effective roughage substitute when it constitutes up to 15% of the total ration. Cattle compensate for the lower energy of sawdust-diluted feed with higher intake. Some sawdusts - poplar is an outstanding example - are partly digestible by cattle. The in vitro digestibility of spruce sawdust is nil, of oak sawdust 5% and of poplar sawdust 30%.
Comparatively mild treatments can markedly increase the digestibility of wood from certain species by exposing the cellulose from the protecting lignin to render it more accessible to attack by cellulose-splitting enzymes. In some woods the cellulose is partly exposed by openings in the lignin which can be widened by swelling. In other woods - for instance, white oak - these openings are plugged and chemical treatments are of little value.

Nutritional tables
Tables of chemical composition and nutritional value 

Avg: average or predicted value; SD: standard deviation; Min: minimum value; Max: maximum value; Nb: number of values (samples) used

IMPORTANT INFORMATION: This datasheet is pending revision and updating; its contents are currently derived from FAO's Animal Feed Resources Information System (1991-2002) and from Bo Göhl's Tropical Feeds (1976-1982).

Main analysis Unit Avg SD Min Max Nb
Dry matter % as fed 92.3 2.2 89.1 94.0 9
Crude protein % DM 0.6 0.4 0.2 1.1 6
Crude fibre % DM 83.2 6.7 74.2 90.0 6
Ether extract % DM 0.6 0.4 0.1 1.2 5
Ash % DM 1.2 1.3 0.1 3.8 8
Gross energy MJ/kg DM 20.5 0.1 17.1 20.5 4 *
 
Ruminant nutritive values Unit Avg SD Min Max Nb
OM digestibility, Ruminant % 59.2 39.1 6.0 94.2 4
ME ruminants (FAO, 1982) MJ/kg DM 9.8 5.6 0.9 14.2 5
Nitrogen digestibility, ruminants % 0.0 0.0 0.0 0.0 5

The asterisk * indicates that the average value was obtained by an equation.

References

AFZ, 2011; Hvidsten, 1946

Last updated on 24/10/2012 00:43:57

Main analysis Unit Avg SD Min Max Nb
Crude protein % DM 1.0 1
Crude fibre % DM 69.8 1
Ether extract % DM 0.4 1
Ash % DM 0.5 1
Gross energy MJ/kg DM 20.1 *

The asterisk * indicates that the average value was obtained by an equation.

References

Nehring et al., 1943

Last updated on 24/10/2012 00:45:24

Main analysis Unit Avg SD Min Max Nb
Crude protein % DM 8.4 8.0 8.8 2
Crude fibre % DM 34.6 22.8 46.3 2
Ether extract % DM 7.4 6.5 8.2 2
Ash % DM 4.3 4.2 4.4 2
Gross energy MJ/kg DM 20.0 *
 
Minerals Unit Avg SD Min Max Nb
Calcium g/kg DM 7.5 7.2 7.8 2
Phosphorus g/kg DM 1.9 1.2 2.6 2

The asterisk * indicates that the average value was obtained by an equation.

References

INFIC, 1978

Last updated on 24/10/2012 00:45:24

Ruminant nutritive values Unit Avg SD Min Max Nb
ME ruminants (FAO, 1982) MJ/kg DM 1.6 1
Nitrogen digestibility, ruminants % 0.0 1

The asterisk * indicates that the average value was obtained by an equation.

References

Kirsch et al., 1941

Last updated on 24/10/2012 00:45:00

References
Datasheet citation 

DATASHEET UNDER CONSTRUCTION. DO NOT QUOTE. http://www.feedipedia.org/node/65 Last updated on June 30, 2010, 0:51

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