Evaluation of various types of forest biomass and wood processing residues as feed for ruminants

Abstract

Eight digestibility trials were performed with rams to evaluate the nutritive values of energy willow leaves (Salix Aqualica), whole short rotation trees (S. Aquatica, S. dasyclados), forest biomass, consisting of branches, foliage and browses, entire hardwood, hydrolysed birch tree pulp and dissolving pulp. The chemical composition of the materials varied according to the leaf-to-wood ratio and the degree of hydrolysis of the pulp. The leaves had high protein contents and low crude fibre contents but remarkably high contents of acid detergent fibre (ADF). The materials containing wood had a high crude fibre content, 41—54 %, as had also both pulps, 44—75 %, but the ADF content was on average 17.4 %-units higher than the content of crude fibre. The lignin content was high in the wood-containing materials (29—34 %) and also high in one of the leaf pulps. The digestibilities of the leaf pulps varied considerably, from 42 to 61 % for DM. The forest biomass had organic matter OM digestibility varying from 20 to 39 %. The digestibility was affected by the ratio of foliage to wood in the material. Hydrolysed wood pulp had poor digestibility, 38 % for OM, but the digestibility of dissolving pulp was comparable to that of good quality roughage, 75 %. The leaf pulps and dissolving pulp had FU values of 0.48—0.69/kg DM. Forest biomass and hydrolysed birch pulp had low values, 0.22—0.34 FU/kg DM. Various energy evaluation systems were compared in the feed value calculations. The fibre correction system gave very low values. Tree foliage and cellulosic wastes with a low lignin content can be utilized as ruminant feed but the possibilities of disposing in this way of cellulosic wastes with high lignocellulosic contents are very limited.