אסיף מאגר המחקר החקלאי

Changes in thioacidolysis products of lignin in wheat straw as affected by SO2 treatment and passage through the gastro-intestine of sheep

Year:

1999

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Volume :

80

Co-Authors:

Yosef, E., Metabolic Unit, Inst. Anim. Sci., ARO, Volcani C., Bet Dangan, Israel
Ben-Ghedalia, D., Metabolic Unit, Inst. Anim. Sci., ARO, Volcani C., Bet Dangan, Israel

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Abstract:

Sheep were fed two rations based on untreated (WS) and SO2-treated (SO2-WS) wheat straw. The neutral detergent fiber (NDF) preparations and water soluble lignins (WSL) isolated from straws, rumen liquor and feces were subjected to thioacidolysis, to study the effect of treatment and passage through the gastro-intestine on monolignol composition of the lignins. SO2 treatment affected guaiacyl (G) and syringyl (S) contents of the straw cell walls with major effect on S, reducing G to 66% and S to 26% of their original concentrations, thus changing the S/G ratio in the CW fraction from 1.6 in WS to 0.64 in SO2-WS. Concomitantly, as a reflection of the above-mentioned there was an increase in the S/G ratio of the WSL, from 0.54 in WS to 1.27 in SO2-WS. Fecal CW residues were richer in p-hydroxyphenyl (H), G and S as compared with the original straw cell walls; the gap being particularly large in the SO2-WS treatment in which the concentrations of monolignols in CW residues were increased by more than ten-fold. The concentration of WSL in the rumen of sheep fed the SO2-WS ration was about eight-fold that found in the rumen of the WS sheep, most likely a result of the combined chemical (SO2) and digestive (rumen microorganisms) effects. Most G and S were found in the CW fraction of the untreated straw, whereas in the SO2-treated straw, the majority of G and S were in the water soluble lignin fraction. In the untreated wheat straw ration (WS), 25.7% of G and 36.6% of S disappeared from the digestive tract. Feed CW-G was higher by 18% and feed CW-S by 60% than the respective fecal CW components in the WS treatment, accompanied by only modest quantitative changes between feed and feces, in the G and S components of WSL. In the SO2-WS treatment, CW-G was increased from 3.48 to 6.26 g/day (by 80%) and CW-S from 2.58 to 6.56 g/day (by 154%) between feed and feces. The digestibility of total acetyl bromide lignin (ABL) was in accord with that of the monolignol data namely, a small proportion (11.4%) of total ABL disappeared from the gastro-intestine of the WS sheep, but a minor, almost negligible percentage (2.94%) of the ABL was digested by the SO2-WS sheep.

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