RUMINANT NUTRITION ▶▶▶


Wood residues in ruminant nutrition


Using wood residue for animal feeding began during World War Two, when there was a severe shortage of feed. The results were not promising, as the animals were not willing to eat these residues, in addition to the low digestibility values. Treating these materials has improved their digestibility and nutritional value.


BY SALAH H. ESMAIL, PHD T


Sugars Glucose Xylose


Mannose Arabinose Galactose


Source: M. R. Abbas (1998) 14 ▶ ALL ABOUT FEED | Volume 29, No. 7, 2021


he wood residues consist of complex carbohydrates whose percentage varies according to the type of trees used and their stage of growth. In general, wood residues consist mainly of cellulose (50%),


hemicellulose (20-30%), and lignin (15-35%), in addition to small amounts of soluble sugars, fatty acids, alcohols, and proteins, particularly in the wood of some trees such as pine and deciduous trees in their early stages of growth.


Processing Various chemical, biochemical, and physical treatments have been suggested to increase the digestibility of wood by ani- mals. These treatments include: • Hydrolysis with various acids to solubilize the cellulose • Alkali and ammonia treatment to saponify the ester bonds and pro-mote swelling beyond the water-swollen dimen- sions to increase micro-biological penetration into the cell wall structure


Table 1 – The percentage of different sugars dissolved in wood molasses.


Average percentage on dry matter basis 12.7 6.8


24.3 8.7 8.6


• Breaking lignin-cellulose chemical bonds with various chemicals to yield a digestible cellulose


• Grinding to very small particle size to alter the crystalline structure of cellulose


• High-energy electron irradiation to break the chemical bonds of the lignin and cellulose


Animal feeding experiments In one study, sawdust of pine, oak, aspen, and other tree spe- cies was included at 10% of the diet of beef steers and this delivered an equivalent performance to diets containing an equal amount of coastal Bermuda grass. However, steers fed 15% sawdust had lower liveweight gains and they consumed slightly less feed than the coastal Bermuda grass-fed animals. In another study, oak sawdust was fed at 5% and 15% of the diet and compared with oyster shells and ground timothy hay as roughage-based feedlot cattle diets. Performance data in- dicated that sawdust could be used successfully at levels up to 15% of the diet without significantly affecting perfor- mance. Coarse ground sawdust delivered better results than fine ground sawdust. For dairy cattle, it has been shown that aspen sawdust can re- place 30% of a conventional diet in dairy cows producing 20 kg of milk daily without reducing the intake of digestible dry matter or the production of milk. Cows consuming the as- pen sawdust also maintained a normal milk fat level. At cer- tain stages in the life cycle of dairy cows, the dilution of the


PHOTO: SHUTTERSTOCK


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