Table 2 – Comparison of the nutritional value of wood molasses and beet molasses when used in feeding fattening lambs.


Weight gain (kg) Feed efficiency Dressing (%)


Source: M. R. Abbas (1998)


For dairy cattle, it has been shown that aspen sawdust can replace 30% of a con- ventional diet in dairy cows without reduc- ing the intake of digestible dry matter and milk production.


diet with wood allowed regulation of energy intake and hence prevented unwanted fattening. In one study, grain in- take was controlled by including up to 45% wood fibre with grain in the diets of dairy cows. Processed wood residues were also added to the diet of fat- tening lambs at a rate of 60% with a resulting increase of 7% in growth rates and a higher digestibility value of the dry matter compared to lambs receiving hay only as a roughage material. These results were attributed to the increase in the net energy of wood after chemical or physical treatment, and also to the increased efficiency of the animal in converting that energy in the rumen into volatile fatty acids (VFA) for use by the animal in growth and other productive purposes post digestion.


Liquid wood residues There are also liquid residues resulting from the manufacture of wood, either by sulfurization to produce cellulose or by pressure with water vapour to produce wood panels. The resulting material, in this case, which is called wood molas- ses, consists mainly of about 65% soluble sugars, which is equivalent to the percentage of sugars found in other types of molasses such as cane, beets, or citrus molasses, thereby providing an important source of energy in animal diets (Ta- ble 1). Wood molasses have been used in some experiments at 10% of the total concentrates of fattening lambs after mix- ing with urea. There were no significant differences in animal


production in the case of feeding wood molasses or other types of molasses, such as beet molasses (Table 2), with no adverse health or metabolic effects on the animal.


Points to consider • Although limited quantities of wood residues or sawdust may be used as a roughage factor or a diluent in ruminant diets, it is evident that most species of wood fed without chemical or physical treatment are unsatisfactory as major components in the ruminant diet. This has caused in- creased interest in the alteration of wood through such treatments to make it more acceptable and digestible by the ruminants.


• Wood residues that have been exposed to chemical treat- ments should be carefully examined for the residual chemi- cals which adversely affect animal health and production.


• Dry wood residues contain only small amounts, or may nearly be devoid, of many essential nutrients. Thus, animals consuming diets with large amounts of wood materials may encounter ill health if the diets are not properly balanced.


• Most of the wood residues are relatively high in moisture, which causes problems in storage because of deterioration. Therefore, research is needed to identify low-cost means of preserving high-moisture wood residues. Preservation through ensiling and the use of mould inhibitors are approaches that might be fruitful.


▶ ALL ABOUT FEED | Volume 29, No. 7, 2021 15


Beet Molasses 0.18 9


52.88


Wood Molasses 0.18 9


52.83


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