The degradation of lignin and quantitative aspects of ruminant digestion

Abstract

I. The technique for the quantitative estimation of lignin by digestion with 72 % H,S04 has been investigated. Two methods of pretreatment designed to eliminate interference products of carbohydrates and proteins were compared, namely (a) acid and pepsin and (6) acid detergent. The latter technique gave low lignin yields owing to the colloidal dispersion of lignin in the acid detergent treatment. Erroneous results arise from an inadequate digestion in 72 yo H,SO,. It was found preferable to filter the product lignin without prior dilution of the acid since white particles of material, assumed to be cellulose, flocculated from solution on dilution. Also there is some loss due to colloidal dispersion of lignin during refluxing in dilute acid.2. Analysis of soda lignin and sulphuric acid lignin preparations from hay, duodenal contents and faeces of sheep with exteriorized flow through a re-entrant duodenal fistula provided evidence for the degradation of lignin by digestive processes. Demethoxylation of lignin occurred mainly in the stomach, suggesting that this was the main site of breakdown. 3.A new displacement method of measuring duodenal flow is described. Quantitative results obtained also indicate that lignin is degraded mainly in the stomach to the extent of about 10 %. 4.These results suggest that faecal lignin is an adequate marker for the estimation of duodenal flow, and hence of the extent of changes in the stomach and intestines respectively.The digestibility of components of the diet in various parts of the ruminant alimentary tract has frequently been studied with lignin as a marker. The possible digestion of lignin is the most serious objection to its use but it has advantages over artificial markers in that it is a natural and integral part of the digesta and food.The routine laboratory method which has most frequently been used for the estima- The present investigations attempt to assess the site and extent of lignin digestion in sheep with re-entrant duodenal fistulas, and the validity of lignin as a natural marker for studies of digestion. Duodenal flow has been measured by a new displacement method, and lignin in food, duodenal contents and faeces has been isolated and analysed . E X P E R I M E N T A L A N D R E S U L T S Chemical studiesMethods of pretreatment for the 72 yo H2S04 digest Faeces and samples of digesta taken from a re-entrant duodenal cannula were freeze-dried and prepared in a finely powdered form by use of a coffee grinder. Finely powdered samples of hay or straw were obtained by chopping, grinding in a hammer mill and finally by treating small samples in a coffee grinder.Two methods of chemical pretreatment of samples were examined. The purpose of both is to remove protein and hydrolysable polysaccharides and so prevent the formation of condensation products during the 72 % H2S04 digest. Isolation of soda lignin and sulphuric acid lignin preparationsMaterials from which lignin preparations were isolated were first subjected to the acid and pepsin pretreatment.I n isolating t...

Effects of time and level of energy supplementation on intake and digestibility of low-quality tall fescue hay by sheep

“…33.5 + 3.76 kg) were surgically fitted with permanently-indwelling ruminal and abomasal cannulae as described by Komarek (1981) Ruminal OM digestion was corrected for the contribution of microbial OM to abomasal digesta; this was accomplished by estimating microbial N in abomasal digesta using a nucleic acid N: total microbial N ratio of 0.2, which Smith et al (1968) reported to be relatively constant (Smith 1975 (Faichney 1975). Previous research using automated total collection procedures supports the validity of this assumption (Porter and Singleton 1971), and Muntifering (1982) (Allden and Jennings 1962;Lamb and Eadie 1979). Limited energy supplementation may have no effect on forage intake, or may even stimulate forage intake (Lee et al 1987 For personal use only.…”

The burial of organic carbon as affected by the evolution of land plants

“…For cattle, for example, the digestibility of forage was found to decline from around 80 to around 30% with increases in lignin contents from 2 to 10% (Jung and Vogel, 1986). Digestion of 10% of fodder lignin has been reported for ruminants (Porter and Singleton, 1971). Earthworms excrete lignin without appreciably degrading it (Crawford, 1981).…”

Comparison of acetyl bromide lignin with acid detergent lignin and Klason lignin and correlation with in vitro forage degradability

“…As already mentioned, the ADL method suffers from partial loss of lignin structure dissolved in the acid detergent solution (Porter and Singleton, 1971;Kondo et al, 1987;Lowry et al, 1994;Moore and Jung, 2001). However, we see no plausible explanation for the KL method results since KL is apparently insensitive to the loss of lignin observed with the ADL procedure, and both results are ash-free residues.…”

“…For legumes, the KL measurements were around 1.5 times over ADL values. Hatfield et al (1994) pointed out that the higher values for grass KL residues were not due only to protein contamination or incomplete hydrolysis of carbohydrates, but were more likely due to the solubilization of lignin components by the ADL treatment, as reported by several other authors (Porter and Singleton, 1971;Lowry et al, 1994;Shimojo and Goto, 1984;Jung et al, 1997;Moore and Jung, 2001). Jung et al (1999) used forage compositional analysis and bomb calorimetry to show that ADL concentrations could not account for sufficient gross energy, indicating that ADL might be an underestimate of lignin content.…”