Maataloustieteellinen Aikakauskirja Vol. 56: 205—212, 1984 Evaluation of various types of forest biomass and wood processing residues as feed for ruminants MATTI NÄSI Department of Animal Husbandry, University of Helsinki, 00710 Helsinki, Finland Abstract. Eight digestibility trials were performed with rams to evaluate the nutritive val- ues of energy willow leaves (Satix Aqualica), whole short rotation trees (S. Aquatica, S. dasy- clados), forest biomass, consisting of branches, foliage and browses, entire hardwood, hydro- lysed 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 contentsbut remarkably high contents of acid deter- gent fibre (ADF). The materials containing wood had a high crude fibre content, 41—54 lr/o, 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 digesti- bility 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 digesti- bility of dissolving pulp was comparable to that of good quality roughage, 75 ®7o . The leaf pulps and dissolving pulp had FU values of 0.48—0.69/kg DM. Forest biomass and hydro- lysed 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 val- ues. 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. Introduction Considerable research has recently been devoted to the use of alternative, non-con- ventional feed sources for animal produc- tion. Wastes from the forest industry and the processing of short-rotation or noncommer- cial trees, and tree residues have received considerable attention as potential feed sources for ruminants (Baker et al. 1975, Kommeri 1981, Pohjonen and Näsi 1983). Browse and foliage are normal food for wild ruminants and also serve to supplement the diets of livestock on pasture. The in vitro Index words: Forestry by-products, forest biomass, wood residues, tree leaves, ruminant nutrition 205 JOURNAL OF AGRICULTURAL SCIENCE IN FINLAND https://www.c-info.fi/en/info/?token=ODGxMonKRqJwYJKj.qTrx6ax14o891BRY9WOBxQ.550H_xvHGy57M3O1H8OVZKmmfy1hJ8tAB-nY1LmRNk1wkqvZRWz8ieBe11s5IWC_AOIFJCVaRBK1XbuzJW8YNf6YIJtDDyU2e5bdTo-bAu09U0lNxqQ44CU4-DQ3YTop6_L-hNQILmd4QTYo4HvmuTACcADcXNKg3vgMdXY digestibility of some tree leaves has been found to be moderate and their protein con- tent high (Nasi and Pohjonen 1981, Ciszuk and Murphy 1982). Tree foliage and the un- lignified sprout biomass of some short rota- tion energy woods have proved to have con- siderable nutritional value (Baertsche 1980) and ensiled green biomass is being investi- gated as a possible forage crop for cattle feeding (Hooper and Winch 1979). Energy wood production and the utilization of whole trees provide large amounts of surplus material of potential value as animal feed. The high cost of pollution control has stimulated active research to evaluate the utilization of waste fibre from the pulping industry as energy feed for ruminants. Cellu- fibre, with a low lignin content, has high digestibility (Saarinen et al. 1959), but waste fibre has usually rather low digestibili- ty and is less palatable to ruminants (Mil- lett et al. 1973, Van Soest and Robertson 1976). The object of the present study was to esti- mate the feed value of some products from short rotation energy willow stands, forest biomass material and wood-processing resi- dues in the diets of ruminants. Materials and methods Eight digestibility trials were conducted with 3 —4 rams to evaluate the feeding values of various forest biomass products and wood processing by-products. The total collection method was used to study the digestibilities of various nutrients. A preliminary accepta- bility period of 10—15 days and a 10-day standardization period were followed by a seven-day collection. In the test period the food intake was reduced to 90 % of average ad libitum intake. The experimental diets and the inclusion of forest biomass materials and wood-pro- cessing by-products were as follows: 1. Leaf pulp from Salix Aquatica foliage, collected in the period 25 Sept. 5 Oct. 1980. Pressed for leaf juice as described by Nasi (1983). The diet consisted of 2500 g leaf pulp and 100 g wheat straw. Intake 46 g DM/kg W 0 75 . 2. Leaf pulp from Aquatica foliage, col- lected between 7 and 17 Sept. 1981 (Nasi 1983). The diet consisted of 2100 g leaf pulp and 100 g oat straw. Intake 44 g DM/kg W 0 3. Foliage and shoots of S. dasyclados. Collected between 10 and 20 Oct. 1981 and stored in bundles when semidried. Chopped before feeding. The diet consisted of 1650 g crushed energy willow and 100 g oat straw. Intake 31 g DM/kg W O7S . 4. Chopped whole small birches and wil- lows, stored in plastic-covered haulms with addition of 1.8 % urea-ureaphosphate in June 1981 (Ettala et ai. 1983). The diet consisted of 1495 g forest biomass and 100 g oat straw. Intake 35 g DM/kg W 0 75 . 5. Chopped whole plants of S. Aquatica collected between 13 and 24 Sept. 1982, stored in large plastic sacks with addition of 2 % urea-ureaphosphate (Ettala 1983 b). The diet consisted of 1055 g of crushed ener- gy willow, 150 g rolled barley and 150 g rape seed meal. Intake 36 g DM/kg W 0 75 . 6. Chopped shoots and foliage of birches and willows collected between 21 June and 20 July 1982. Stored in plastic covered halms with addition of 2.0 % urea-ureaphosphate. The diet consisted of 1115 g forest biomass and 150 g rolled barley and 150 g rape-seed meal. Intake 37 g DM/kg W 0 75 . 7. Birch tree pulp hydrolysed with acetic acid. The diet consisted of 410 g pelleted fibre, 875 g hay and 100 g soy bean meal. In- take 50 g DM/kg W 0 75 . 8. Dissolving pulp, dehydrated screen re- jected. The diet consisted of 420 g pulp, 845 g hay and 100 g soy bean meal. Intake 45 g DM/kg W 0 75 . The 7-day faecal collections were weighed daily, mixed thoroughly and subsampled for later analysis. Urine was collected in pails 206 207 containing 30 ml of 10 N H 2S04 and a 5 °7o aliquot sample of daily urine was saved for nitrogen analysis. Feed samples were also collected daily during each collection period and pooled for chemical analysis. Dry matter contents were determined by oven heating at 103 °C and samples for feed analyses were dried in a vacuum oven at 50 °C. The feed analyses were made on the dried samples by standard methods. Acid deter- gent fibre (ADF), neutral detergent fibre (NDF) and lignin (ADL) were determined ac- cording to Coering and Van Soest (1970). Crude lignin and water-soluble carbohydrates were determined as described by Salo (1965). Analyses for tannin were made by the Official method of analysis (Anon 1970). In vitro digestibilities were determined by the method of Tilley and Terry (1963). The digestibility coefficients were calcu- lated from the difference in the digestibility of the total diet, on thebasis of the measured or table values of the basic feed. Net energy values were calculated according to Breirem (1969), Van Es (1978), Salo et ai. (1982) and Möller et ai. (1983) and values for me- tabolizable energy according to Maff (Anon 1975). Results and discussion The chemical composition of the various forestry and wood-processing by-products is presented in Table 1. The two first materials are pulped willow leaves, the four following are chopped foliage with wood material and the two last processed wood fibre, so that the composition of the materials thus varies a good deal. The crude protein varied accord- ing to the amount of foliage in the material and to the urea-ureaphosphate used as pre- servative. The willow leaf pulp had a high value for true protein, on average 18.2 %, while the wood pulp materials had a very low value. The products containing wood material (nos. 3—6) had high crude fibre contents (41.0—54.2 %) and the dissolving material, Table 1. Chemical composition of different forestry by-products (% of dry matter). S. Aquatica S. Aquatka S. dasyclados Forest biomass S. Aquatka Forest biomass Hydrolysed Dissolving leaf pulp leaf pulp chopped chopped chopped chopped wood pulp pulp 1980 1981 whole plant whole trees whole plant shoots and 1981 1981 1982 foliage 1982 Dry matter 32.6 36.6 31.9 49.7 32.0 43.6 89.2 9.6 Ash 6.7 5.6 5.0 2.6 5.5 3.6 5.1 1.4 Crude protein 20.6 18.5 14.6 10.1 31.2 26.7 7.9 0.8 True protein 19.4 16.9 12.8 7.5 13.8 15.0 Ether extract 5.7 4.6 1.3 1.3 1.2 3.4 1.9 4.5 Crude fibre 15.2 18.5 40.7 54.2 41.6 41.0 43.9 74.9 N.F.E. 51.8 52.9 38.4 31.9 20.5 36.2 41.1 18.5 Acid detergent fibre 29.3 45.9 64.5 71.6 62.8 60.1 50.2 84.5 Neutral detergent fibre 30.3 46.2 70.1 85.6 77.1 72.1 69.1 89.1 Acid detergent lignin 12.9 26.3 28.6 30.7 35.8 25.5 9.3 0.7 Crude lignin 17.9 29.9 29.2 29.6 34.2 25.5 11.1 1.8 Water-soluble carbohydr. 11.2 0.9 0.7 0.6 1.4 0.9 3.9 0.3 Tannins 2.3 2.6 1.5 0.9 0.9 0.9 1.1 which is almost pure cellulose, had 75 %. Crude fibre is not a good indicator of the feed value of a material, owing to its high content of lignocellulose components. The analytical technique worked out by Coering and Van Soest (1970) enables more detailed studies and evaluation of different complex carbohydrate fractions and lignin. On aver- age the ADF contents exceeded the crude fibre contents by 17.4 %-units. The lignin content was high in the wood-containing ma- terials (29 —34 %), but also high in the leaf pulp of the later year. The lignin values are somewhat higher that those presented by Van Soest and Robertson (1976). The tannin content of the leaf pulp aver- aged 2.5 % which exceeds the value for the other materials. Tannin compounds can ap- parently reduce protein digestibility and im- pair the voluntary intake (Me Leod 1974, Van Soest and Robertson 1976). Tannin can also influence cellulose digestion through inhibition of microbes and formation of a tannin-cellulose complex (Me Leod 1974). Here, the intakes of diets containing leaf pulp averaged 45 g DM/kg W 0 75; the value with forest biomass averaged 35 g DM and for those with cellufiber 47 g DM. The intakes were low but comparable to the results of ex- periments made by Nastis and Malechek (1981) and Wilson (1977). Two sheep on diet no 4 refused to eat forest biomass and one on diet no. 7 refused to eat hydrolysed wood pulp and had to be removed from the experiment. All animals on diets nos. 3—7 lost weight during the collection period. This can also be seen from the results for the ni- trogen balance, which were negative (Ta- ble 2). The digestibility coefficients (Table 2) are calculated from the difference in the total diet digestibilities. The digestibilities of the two willow leaf pulps differed considerably (61 —42 ®7o for OM). The pulp of the later year was contamined by rust and the lignin content was twice as high as in the first leaf pulp. The digestibilities correspond to the re- suits presented for various energy tree leaves (Näsi and Pohjonen 1981) and to the values for various tree leaves of natural stands (Nehring 1965, Ciszuk and Murphy 1982). The suitable chemical composition, especial- ly the low crude fibre content, suggests a higher digestibility for leaves, but the rather high lignin content (18 —30 %) and the con- tents of tannins reduce digestibility. The digestibility of forest biomass depends on the ratio of foliage to wood in the mate- rial. The separation of wood material from foliage was very difficult and thus digesti- bilities were low, 20—39 % for OM. Unmo- dified mature hardwood sawdust is totally indigestible because of the association of cel- lulose and hemicellulose with lignin (Van Soest and Robertson 1976, Nehring 1965 a) Young hardwood and browse are digestible to some extent, because the bark and cam- bial layers contain soluble carbohydrates, and unlignified twigs are also digested (Hoo- per and Winch 1979, Baertsche 1980, Singh and Kamstra 1981). In mature wood, 70 —80 % of DM consists of carbohydrates: cellulose, hemicellulose and a small amount of sugars, but without pretreatment only a small proportion of these carbohydrates is available for digestion by the rumen microbes (Scott et al. 1969, Millett et al. 1970). Baertsche (1980) presents quite a high di- gestibility value for short-rotation poplar biomass, 54 % for OM, 52 % for CP and 35 % for ADF, but Hooper and Winch (1979) found lower values for bark and wood, 28—42 <7o for DM, and 67 % for the DM of leaves. Wylie (1981), however, ob- tained the very low value of 13 % for DM di- gestibility of energy willow biomass. In this study hydrolysed wood pulp had rather a low digestibility. The lignin content was 11.1 %, which indicated that acetic acid hydrolysis had been ineffective. The digesti- bility of dissolving pulp was comparable to that of good quality roughage. Baker et al. (1975) reported that the digestibility in vitro of many pulp and paper-making residues 208 Table 2. Digestibility coefficients of different forestry by products, and nitrogen balance and biological values of diets. S. Aquatica S. Aquatica S. dasyclados Forest biomass S. Aquatica Forest biomass Hydrolyzed Dissolving leaf pulp leaf pulp chopped chopped chopped chopped wood pulp pulp 1980 1981 whole plant whole trees whole plant shoots and n = 3 n = 4 n = 3 n = 3 n = 3 1981 n = 3 foliage 1982 n = 1 n = 4 Dry matter x 56.7 42.0 25.1 35.0 38.2 17.2 38.2 77.3 s.d. 1.0 0.3 7.2 5.0 9.2 2.8 8.7 Organic matter x 61.3 42.2 26.2 37.6 38.7 19.5 37.9 75.0 s.d. 0.6 1.0 7.9 4.2 8.9 4.1 6.7 Crude protein x 51.9 36.3 37.2 27.0 64.6 38.5 65.7 0 s.d. 1.3 3.5 7.6 0.6 8.9 11.6 Ether extract x 74.0 62.1 22.4 38.1 54.9 30.9 61.2 6.7 s.d. 0.7 4.0 14.5 7.2 11.4 4.5 6.3 Crude fibre x 49.3 39.0 27.2 43.7 28.8 19.3 20.7 67.3 s.d. 1.4 1.1 7.9 3.5 10.7 2.4 6.3 N.F.E. x 66.3 43.1 19.9 27.2 21.3 33.5 42.0 26.5 s.d. 1.2 2.0 8.3 13.7 9.3 5.1 12.8 Nitrogen balance x 0.2 2.6 —2.9 —8.2 —9.5 —B.O 3.20 —0.51 s.d. 0.7 2.8 0.3 0.2 2.8 0.90 0.65 Biological value x 41.7 66.4 37.8 —ll.B —13.5 —6.9 55.8 65.9 s.d. 4.8 17.5 4.0 1.2 15.4 2.6 3.6 In vitro digestibility Dry matter 69.2 42.3 28.6 18.6 42.9 28.7 47.1 35.0 Organic matter 57.3 39.7 25.6 16.7 39.9 26.4 46.4 34.6 209 210 Table 3. Calculated feed values of different forestry by-products. S. Aquatica S. Aquatica S. dasyclados Forest biomass S. Aquatica Forest biomass Hydrolysed Dissolving leaf pulp leaf pulp chopped chopped chopped chopped wood pulp pulp 1980 1981 whole plant whole trees whole plant shoots and 1981 1981 1982 foliage 1982 Value number-syst. FU/kg DM 0.687 0.479 0.227 0.334 0.342 0.296 0.322 0.643 kg/FU 4.47 5.71 13.81 6.03 9.15 7.76 3.49 16.18 DCP in feed 3.49 2.46 1.73 1.36 6.45 4.48 4.64 0 g DCP/FU 156 140 239 82 590 348 162 0 Fiber correclion-syst. FU/kg DM 0.720 0.429 0.023 0.017 0.145 0.080 0.077 0.118 kg/FU 4.26 6.37 135.3 116.2 21.6 28.8 14.5 88.0 Danish-system FE K 0.672 0.326 —O.OOl 0.131 0.326 0.177 0.163 0.364 van Es-system NEW MJ/kg DM 4.68 2.61 1.23 2.17 2.93 1.97 1.91 4.47 NEL MJ/kg DM 4.88 3.18 1.89 2.79 3.45 2.61 2.55 4.72 MAFF-system MJ ME/kg DM 8.54 5.64 3.08 4.96 5.24 4.25 4.48 8.40 ranged from 45 of 65 % but some attained levels as high as 90 %. The feed values calculated for the differ- ent forestry by-products and pulps are pre- sented in Table 3. For comparison, the net energy values are calculated by four different methods. The number values were calculated from equations presented by Van Es (1978) as the ratio of GE to ME for production and maintenance in relation to barley. The num- ber value for leaf pulps averaged 0.80, for forest biomass and hydrolysed pulp 0.65 and for dissolving pulp 0.80. The FU k values were calculated from values for digestible energy corrected for digestible fibre (Möl- ler et ai. 1983). Leaf pulp and dissolving pulp had FU values of 0.48—0.69/kg DM, corresponding to hay. Whole chopped ener- gy willows and hydrolysed wood pulp had low values, 0.22—0.34 FU/kg DM. The fibre correction system gave very low energy val- ues, 0.02—0.15 FU. The possibilities of disposing of cellulosic wastes from forestry by feeding them to ru- minants are limited at present. Materials with low digestibility, such as lignocellulose wastes, must be made more digestibile by chemical or biological techniques before they can be utilized by ruminants, and in practice processing costs may be prohibitive. High quality cellulosic wastes with a low lignin content can be removed from the environ- ment by ruminant feeding. Browses and foli- age can be eaten by animals put out to pas- ture. References Anon 1970. Official methods of analysis. Ass. Offic. Anal. Chem. p. 513. , 1975. Energy allowances and feeding systems for ru- minants. Min. Agric. Fish. Food. Techn. Bull. 33. Baertsche, S.R. 1980. The potential utilization of short rotation biomass produced trees as a feed source for ruminants. A Thesis. Michigan State University. 113 p. Baker, A.J., Millett, M.A. & Satter, C.D. 1975. Wood and wood-based residues in animal feeds. Amer. Chem. Soc. Sym. Ser. Cellulase Technol. Res. No 10. 75 p. Breirem, K. 1969. Nettoenergie bei Mast und Grund- lage der Futterbewertung. Handbuch der Tierernäh- rung 1:611—652. Paul Parey. Hamburg. Coerino, H.K. & Van Soest, P.J. 1970. Forage fiber analysis: apparatus, reagents, procedures and some applications. U.S. Dep. Agric. Handb. No 379: B—9. Ciszuk, P. & Murphy, M. 1982. Digestion of crude pro- tein and organic matter of leaves by rumen microbes in vitro. Swedish J. Agric. Res. 12: 35—40. Es A.J.H. van. 1978. Feed evaluation for ruminants 1. The systems in use from May 1977 onwards in the Netherlands. Livestock Prod. Sci. 5: 331 —345. Ettala, E., Tuomikoski, T, & Näsi, M. 1983 a. Metsä- ja maatalouden sivutuotteita lihamullien rehuna I. Maaseudun Tulevaisuus 6.10. 1983. p. 4. —, Virtanen, E. & Näsi, M. 1983 b. Metsä- ja maata- louden sivutuotteita lihamullien rehuna 11. Maaseu- dun Tulevaisuus 8.10. 1983. p. 4. Hooper, G. S. & Winch, J.E. 1979. Hybrid poplar as a forage crop for cattle feeding. Rep. 29 in Poplar re- search Management and Utilization in Canada. Onta- rio Min. Nat. Res. Forest Res. Inf. Paper No 102 (29): I—s. Kommeri, M. 1981. Puunjalostusteollisuuden jätekui- dun hyödyntäminen kotieläintaloudessa. Kotieläin- hoidon tutkimuslaitoksen tiedote No 14. 57 p. Mc Leod, M.N. 1974. Plant tannins their role in forage quality. Nutr. Abstr. Rev. 44: 803—815. Millett, M.A., Baker, A.J., Fenst, W.C., Mellenber ger, R.W. & Satter, L.D. 1970. Modifying wood to increase its in vitro digestibility. J. Anim. Sci. 31: 781—788. —, Baker, A.J., Satter, L.D., McGovern, J.N. & Di nius, D.A. 1973. Pulp and papermaking residues as feedstuffs for ruminants. J Anim. Sci. 37: 599—607. Möller, P.D., Andersen, P.E., Hvelplund, T., Mad- sen, J. & Thomsen, K.V. 1983. En ny beregnings- metode dor fodermidlernes energivaerdi til kvaeg FE k . 555 Ber. fra Statens Husdyrbrugsf. 60 p. Nastis, A.S. and Malechek, J.C. 1981. Digestion and utilization of nutrients in oak browse by goats. J. Anim. Sei. 53: 283—289. Nehring, K. 1965 a. Laub- und Reisigfutterstoffe. Handbuch der Futtermittel 2: 10—27. Paul Parey. Hamburg. —, 1965 b. Futterstoffe aus Holz und Cellulose. Hand- 211 buch der Futtermittel 2: 106—117. Paul Parey. Ham- burg. Näsi, M. 1983. Leaf protein production from energy willow leaves. J. Scient. Agric. Soc. Finl. 55: 155 162, —, & Pohjonen, V. 1981. Green fodder from energy forest farming. J. Scient. Agric. Soc. Finl. 53: 161 167. Pohjonen, V. & Näsi, M. 1983. Wet biomass as animal feed Fodder as a by-product from energy forest. Forestry Energy Agreement International Energy Agency. Programme group B Biomass growth and production. Ontario Tree Improvement and Forest Biomass Institute. Min. of Nat. Res. Maple. Ontario Canada Rep. 1 (1983): 1—22. Saarinen, P., Jensen, W. & Alhojärvi, J. 1959. On the digestibility of high yield chemical pulp and its evalua- tion. Acta Agr. Renn. 943: 1—23. Salo, M.-L. 1965. Determination of carbohydrate frac- tions in animal foods and faeces. Acta Agr. Fenn. 105: 1 102. —, Tuori, M & Kiiskinen, T. 1982. 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Ms received August 17, 1984 SELOSTUS Erilaisten metsätalouden ja puunjalostus- teollisuuden sivutuotteiden arvo märehtijäin rehuna Matti Näsi Helsingin yliopisto, kolieläinlieleen laitos, 00710 Helsinki Tutkimuksessa selvitettiin energiapajun lehtien (Salix Aquatica), koko energiapuun (S. Aquatica, S. dasy- clados), metsäbiomassan, joka koostui varvuista, leh- distä japuuaineksesta, hydrolysoidun puukuidun ja vis- koosikuidun koostumusta, sulavuutta ja rehuarvoa. Pa- junlehtien valkuaispitoisuus oli korkea((18.20.65 —20.6 %) kun taas puukuitujen valkuaispitoisuus oli alhainen. Puuainesta sisältävien tuotteiden kuitupitoisuus oli kor- kea((41.54.20 —54.2 %) ja viskoosikuitu, joka on lähes puh- dasta selluloosaa, sisälsi raakakuitua 74.9 %. Ligniini- pitoisuus oli puuainesta sisältävissä tuotteissa niinikään korkea (29—34 %), mutta myös pajunlehdissä oli pal- jon ligniiniä (18—30 %). Tuotteista määritettiin myös happo- ja neutraalidetergenttikuitu. Eri tuotteiden sulavuus määritettiin kahdeksana sula- vuuskokeena 3—4 pässillä. Pajunlehtiä sisältävillä ruo- kinnoilla pässit söivät keskimäärin 45 g kuiva-ainetta metabolista elopainokiloa kohti, ja vastaavasti puuai- nesta sisältäviä eri metsäbiomassoja 35 g sekä puukuitu- ja sisältävää diettiä 47 g. Pajunlehtien orgaanisen aineen sulavuus vaihteli 42 —61 % ja eri metsäbiomassoilla 20—39 %. Sulavuuteen vaikutti lehtien ja puuaineksen suhde eri metsäbiomassoissa. Etikkahapolla hydrolysoi- tu puukuitu suli huonosti (38 %), mutta viskoosikuitu huomattavasti paremmin (75 %). Pajunlehtien ja vis- koosikuidun rehuyksikköarvoksi saatiin 0.48—0.69/kg ka. Metsäbiomassojen ja hydrolysoidun kuidun ry-ar- voksi saatiin 0.22—0.34/kg ka. Eri energia-arvon lasku- tapoja verrattiin keskenään, ja laskutavasta riippuen saatiin erilaisia tuloksia. Puunlehtiä ja vähän ligniiniä sisältävää selluloosakui- tua voidaan käyttää märehtijöiden rehuna. Sitävastoin puuainesta tai lievästi hydrolysoitua puukuitua ei voida käyttää rehuna alhaisen sulavuuden takia. 212