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In Vitro Evaluation of Chemically-Treated Poplar Bark¹

University of Minnesota^,4, St. Paul 55108

Abstract

The effects of different chemicals, their concentrations and reaction times (1 day or 150 days) on composition and digestibility of poplar bark in vitro were studied. The chemical treatments used were NaOH, NaOH+S, Na₂S, Na₂SO₃, Na₂SO₃+Na₂CO₃, CaO, CaO+NaOH, NaC10 and NaC10₂. Chemical concentrations ranged from 0 to 30 g/100 g bark on a dry matter basis. Treatment for 1 day with the higher concentrations of NaOH, CaO and CaO+NaOH decreased lignin (from 21.1% to 16.9, 19.7 and 20.7%, respectively) and hemicellulose (from 12.1% to 4.4, 6.6 and 7.0%, respectively). Na10 and NaC10₂ decreased lignin from 21.1% to 12.4 and 12.4%, respectively. Na₂S increased NDF content from 66.8 to 74.1% and ADF content from 54.7 to 60.1%. Na₂SO₃ and Na₂SO₃+Na₂CO₃ had little or no effect on chemical components. Treatment for 150 days with the higher concentrations of NaOH,CaO or CaO+NaOH decreased cellulose (from about 33.7% to 30.3, 28.7 and 30.7%, respectively), hemicellulose (from 11.5% to 5.9, 6.2 and 2.2%, respectively) and lignin (from 22.9% to 17.5, 17.3 and 16.4%, respectively). Na₂SO₃+Na₂CO₃ increased cellulose from 33.5 to 36.4% and decreased hemicellulose from 11.5 to 8.3%; Na10 decreased cellulose from 33.5 to 28.7% and lignin from 22.9 to 14.6% and NaC10₂ decreased the lignin content of the bark from 22.9 to 11.9%.

In general, Na₂S, Na₂SO₃ and Na₂SO₃+Na₂CO₃ had little or no effect on the in vitro digestibility of poplar bark. In vitro digestibility of poplar bark was increased to the greatest extent (24 to 33%) by NaOH, CaO, CaO+NaOH, Na10 or NaC10₂ treatments. However, longer reaction times were required to achieve maximum in vitro digestibilities with CaO or CaO+NaOH treatments than with NaOH.

¹ Paper No. 8728 of the Scientific Journal Series of the Minnesota Agricultural Experiment Station.

² Present address: College of Agriculture, University of Basrah, Iraq.

^₃ Present address: Department of Animal Production, Ein-Shams University, Cairo, Egypt.

⁴ Department of Animal Science.