Xuezhao Sun - Academia.edu (original) (raw)

Papers by Xuezhao Sun

Scientific reports, 2015

Ruminant livestock are important sources of human food and global greenhouse gas emissions. Feed ... more Ruminant livestock are important sources of human food and global greenhouse gas emissions. Feed degradation and methane formation by ruminants rely on metabolic interactions between rumen microbes and affect ruminant productivity. Rumen and camelid foregut microbial community composition was determined in 742 samples from 32 animal species and 35 countries, to estimate if this was influenced by diet, host species, or geography. Similar bacteria and archaea dominated in nearly all samples, while protozoal communities were more variable. The dominant bacteria are poorly characterised, but the methanogenic archaea are better known and highly conserved across the world. This universality and limited diversity could make it possible to mitigate methane emissions by developing strategies that target the few dominant methanogens. Differences in microbial community compositions were predominantly attributable to diet, with the host being less influential. There were few strong co-occurrenc...

Scientific reports, 2015

Ruminant livestock are important sources of human food and global greenhouse gas emissions. Feed ... more Ruminant livestock are important sources of human food and global greenhouse gas emissions. Feed degradation and methane formation by ruminants rely on metabolic interactions between rumen microbes and affect ruminant productivity. Rumen and camelid foregut microbial community composition was determined in 742 samples from 32 animal species and 35 countries, to estimate if this was influenced by diet, host species, or geography. Similar bacteria and archaea dominated in nearly all samples, while protozoal communities were more variable. The dominant bacteria are poorly characterised, but the methanogenic archaea are better known and highly conserved across the world. This universality and limited diversity could make it possible to mitigate methane emissions by developing strategies that target the few dominant methanogens. Differences in microbial community compositions were predominantly attributable to diet, with the host being less influential. There were few strong co-occurrenc...

Annals of Animal Science, 2015

PLOS ONE, 2015

The objectives of this study were to examine long-term effects of feeding forage rape (Brassica n... more The objectives of this study were to examine long-term effects of feeding forage rape (Brassica napus L.) on methane yields (g methane per kg of feed dry matter intake), and to propose mechanisms that may be responsible for lower emissions from lambs fed forage rape compared to perennial ryegrass (Lolium perenne L.). The lambs were fed fresh winter forage rape or ryegrass as their sole diet for 15 weeks. Methane yields were measured using open circuit respiration chambers, and were 22-30% smaller from forage rape than from ryegrass (averages of 13.6 g versus 19.5 g after 7 weeks, and 17.8 g versus 22.9 g after 15 weeks). The difference therefore persisted consistently for at least 3 months. The smaller methane yields from forage rape were not related to nitrate or sulfate in the feed, which might act as alternative electron acceptors, or to the levels of the potential inhibitors glucosinolates and S-methyl L-cysteine sulfoxide. Ruminal microbial communities in forage rapefed lambs were different from those in ryegrass-fed lambs, with greater proportions of potentially propionate-forming bacteria, and were consistent with less hydrogen and hence less methane being produced during fermentation. The molar proportions of ruminal acetate were smaller and those of propionate were greater in forage rape-fed lambs, consistent with the larger propionate-forming populations and less hydrogen production. Forage rape contained more readily fermentable carbohydrates and less structural carbohydrates than ryegrass, and was more rapidly degraded in the rumen, which might favour this fermentation profile. The ruminal pH was lower in forage rape-fed lambs, which might inhibit methanogenic activity, shifting the rumen fermentation to more propionate and less hydrogen and methane. The significance of these two mechanisms remains to be investigated. The results suggest that forage rape is a potential methane mitigation tool in pastoral-based sheep production systems.

ABSTRACT Perennial ryegrass is the principal component of diets fed to ruminants in New Zealand. ... more ABSTRACT Perennial ryegrass is the principal component of diets fed to ruminants in New Zealand. Selection for ryegrass improvement should incorporate measures relating to feeding value (i.e. quality×intake) for sheep and cattle. This study was designed to measure the variation in characteristics of nutritive value of three ryegrass cultivars harvested at different stages of regrowth. The cultivars were Grasslands Greenstone (Greenstone; tetraploid), Grasslands Samson (Samson; diploid) and Quartet (tetraploid). They were grown as pure swards with leafy regrowth harvested after 2, 3, 4, 5, 6 and 7 weeks for measurement of chemical composition, physical parameters (i.e. shear force and energy required for mincing), degradation kinetics and distribution of constituents between the immediately degradable (A), potentially degradable (B) and undegradable (C) fractions. Analyses showed that age of regrowth resulted in larger differences in composition and degradation kinetics than cultivar, and emphasised the need to harvest material in a similar condition to that grazed by animals. Cultivar differences were best indicated by chemical composition and ratios of crude protein (CP):neutral detergent fibre (aNDF) in the dry matter (DM), the proportion of CP in the ‘A’ fraction as well as degradation of DM in the ‘B’ fraction. The CP:aNDF ratios averaged for the three cultivars at 2, 3, 4, 5, 6, and 7 weeks were 0.82, 0.76, 0.71, 0.55, 0.48 and 0.42, respectively, with averages at weeks 5 and 6 for Greenstone, Samson and Quartet of 0.59, 0.49 and 0.48, respectively. The ratio differed between ages (P

Published reports of CH4 yields as g CH4/kg dry matter (DM) intake suggest that emissions from sh... more Published reports of CH4 yields as g CH4/kg dry matter (DM) intake suggest that emissions from sheep fed fresh forage chicory (Cichorium intybus) are about 30% lower than from those fed fresh ryegrass. In this study, 2 year old wethers (16; 54±3.8kg liveweight) were fed either mature chicory or perennial ryegrass at 1.3 times maintenance metabolisable energy requirements in the

ABSTRACT Forage chicory (Cichorium intybus) has the potential to mitigate methane emissions from ... more ABSTRACT Forage chicory (Cichorium intybus) has the potential to mitigate methane emissions from ruminants. It was reported that the reduction can be up to 30% compared with perennial ryegrass (Lolium perenne). To accurately evaluate the reduction, fresh chicory and perennial ryegrass in the vegetative state were fed to 24 wethers, 8 of which rumen-fistulated, at 1.3 and 2.2 times maintenance metabolisable energy requirements. Dry matter (DM) intake, whole tract apparent digestibility, rumen fermentation parameters and rumen liquid passage rate were measured in metabolism crates, and methane emissions determined using a calorimetric technique. Chemical analyses showed that chicory contained less DM, organic matter (OM), crude protein, neutral detergent fibre (aNDF), acid detergent fibre (ADF), cellulose and hemicellulose, but more hot water-soluble carbohydrate and pectin, than perennial ryegrass. Methane yield (g/kg DM intake) of wethers fed chicory did not differ from that of those fed perennial ryegrass. Yield was lower at the high versus the low feeding level of ryegrass. Apparent digestibility of DM and OM was higher, and aNDF, ADF, hemicellulose and cellulose was lower, in wethers fed chicory versus perennial ryegrass. In situ DM degradation rate of chicory was higher than that of perennial ryegrass. Rumen liquid passage rate was the same for wethers fed the two forages and higher at the high feeding level. The reduction in methane emissions by feeding vegetative chicory to wethers was limited, but increased feeding level reduces methane yields per unit of DM intake.

Journal of the Science of Food and Agriculture, 2007

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Journal of Applied Microbiology, 2008

Aims: Determine the susceptibility of forage chicory (Cichorium intybus L.) to degradation by rum... more Aims: Determine the susceptibility of forage chicory (Cichorium intybus L.) to degradation by ruminal fibrolytic bacteria and measure the effects on cell-wall pectic polysaccharides. Methods and Results: Large segments of fresh forage chicory were degraded in vitro by Lachnospira multiparus and Fibrobacter succinogenes, but not by Ruminococcus flavefaciens or Butyrivibrio hungatei. Cell-wall pectins were degraded extensively (95%) and rapidly by L. multiparus with a simultaneous release of uronic acids and the pectin-derived neutral monosaccharides arabinose, galactose and rhamnose. Fibrobacter succinogenes also degraded cell-wall pectins extensively, but at a slower rate than L. multiparus. Immunofluorescence microscopy using monoclonal antibodies revealed that, after incubation, homogalacturonans with both low and high degrees of methyl esterification were almost completely lost from walls of all cell types and from the middle lamella between cells. Conclusions: Only two of the four ruminal bacteria with pectinolytic activity degraded fresh chicory leaves, and each showed a different pattern of pectin breakdown. Degradation was greatest for F. succinogenes which also had cellulolytic activity. Significance and Impact of the Study: The finding of extensive removal of pectic polysaccharides from the middle lamella and the consequent decrease in particle size may explain the decreased rumination and the increased intake observed in ruminants grazing forage chicory.

Grass and Forage Science, 2012

ABSTRACT Grasses with fast fibre degradation are required by intensive pasture‐based animal produ... more ABSTRACT Grasses with fast fibre degradation are required by intensive pasture‐based animal production systems to maximize intakes and productivity. To select fast‐degrading elite cultivars, a repeatable, rapid and inexpensive screening method should be developed, so large numbers of samples can be evaluated. This study refined the experimental procedure for the in sacco incubation technique using fresh (not dried) perennial ryegrass (Lolium perenne L.). Pre‐ruminal incubation treatment and ratio of forage weight to the surface area of the in sacco bag have been tested to evaluate their effects on ryegrass degradation kinetic parameters in the bovine rumen. The timing of sampling and the number of sampling time points were also examined. Results indicated that warming the bags in water prior to incubation led to a faster dry‐matter (DM) degradation in the first 12 h. If ratio of forage to bag surface area was between 26 and 45 mg DM cm−2, degradation parameters were not affected by bag fill. Sampling between 9 and 12 h was critical for determining degradation rate. From these results, an improved in sacco incubation procedure is recommended for screening of ryegrasses used for cultivar selection. The principles demonstrated here for ryegrass may be applicable to other forages, although the critical sampling times for measuring degradation rate are likely to differ.

animal, 2013

Water-soluble components of feedstuffs are mainly utilized during the early phase of microbial fe... more Water-soluble components of feedstuffs are mainly utilized during the early phase of microbial fermentation, which could be deemed an important determinant of gas production behavior in vitro. Many studies proposed that the fractional rate of degradation (FRD) estimated by fitting gas production curves to mathematical models might be used to characterize the early incubation for in vitro systems. In this study, the mathematical concept of FRD was developed on the basis of the Logistic-Exponential (LE) model, with initial gas volume being zero (LE0). The FRD of the LE0 model exhibits a continuous increase from initial (FRD 0) toward final asymptotic value (FRD F) with longer incubation time. The relationships between the FRD and gas production at incubation times 2, 4, 6, 8, 12 and 24 h were compared for four models, in addition to LE0, Generalization of the Mitscherlich (GM), c th order Michaelis-Menten (MM) and Exponential with a discrete LAG (EXPLAG). A total of 94 in vitro gas curves from four subsets with a wide range of feedstuffs from different laboratories and incubation periods were used for model testing. Results indicated that compared with the GM, MM and EXPLAG models, the FRD of LE0 model consistently had stronger correlations with gas production across the four subsets, especially at incubation times 2, 4, 6, 8 and 12 h. Thus, the LE0 model was deemed to provide a better representation of the early fermentation rates. Furthermore, the FRD 0 also exhibited strong correlations (P < 0.05) with gas production at early incubation times 2, 4, 6 and 8 h across all four subsets. In summary, the FRD of LE0 model provides an alternative to quantify the rate of early stage incubation, and its initial value could be an important starting parameter of rate.

Animal Production Science, 2011

ABSTRACT Fast degrading perennial ryegrass (Lolium perenne L.) is a desirable characteristic to s... more ABSTRACT Fast degrading perennial ryegrass (Lolium perenne L.) is a desirable characteristic to select for because it can result in increased feed intake by grazing ruminants. Sufficient range in genotypic variation of dry matter (DM) degradation kinetics is a prerequisite for selection. To investigate the genotypic variation, 77 perennial ryegrass accessions sourced internationally, grown in autumn in the same conditions and harvested in the vegetative state, were examined using an in sacco technique. From the time course of DM disappearance, soluble fraction ‘A’, potentially degradable fraction ‘B’, indigestible fraction ‘C’ and the degradation rate k of fraction ‘B’ were estimated. The results indicated that a large range in genotypic variation was present in all degradation parameters. Fraction ‘A’ ranged from 0.48 to 0.60, with the highest five accessions being 21% higher than the lowest five. Degradation rate k of fraction ‘B’ ranged from 0.069 to 0.199/h, with the fastest five being 125% higher than the slowest five. There were no strong correlations between degradation parameters and chemical composition. In conclusion, there was considerable genotypic variation in DM degradation kinetics among perennial ryegrass accessions and this presents plant breeders with ample opportunity to select for fast degrading perennial ryegrasses.

Animal Feed Science and Technology, 2013

ABSTRACT Hydrogen (H-2) is produced in the rumen during the microbial fermentation of dietary car... more ABSTRACT Hydrogen (H-2) is produced in the rumen during the microbial fermentation of dietary carbohydrates, and is consumed as an energy source by H-2-using microbes, especially the methane (CH4)-forming methanogens. In vitro fermentation systems are used to study some aspects of rumen activity, and the kinetics of H-2 accumulation in these systems is a balance between H-2 production and consumption. The fate of H-2 produced during fermentation is either as dissolved H-2 in the liquid phase (dH(2)) or H-2 gas (gH(2)). This study proposes a mathematical model of the processes leading to gH(2) accumulation. The gH(2) was mathematically divided into a dissolvable (x) and non-dissolvable (y) gH(2) fractions. The gH(2) in fraction x was assumed to be available to re-dissolve into the liquid phase and therefore could be consumed by H-2-using microbes. The gH(2) in fraction y represents gH(2) that does not re-dissolve into the dH(2) pool, and thus biologically unavailable for the H-2-using microbes. Our model was developed to describe the changes in gH(2) in an in vitro fermentation system, based on gH(2) production and re-solution. Seven very different profiles of in vitro gH(2) curves were selected to demonstrate the applicability of the new model, including gH(2) accumulation profiles from two feeds and three methanogen inhibitors. The three inhibitors reduced CH4 production in different ways: by partial inhibition of methanogens (bromoethane sulphonate), by complete inhibition of methanogens (root of Rheum palmatum), or by acting as a hydrogen sink (nitrate added as NH4NO3). The new model fitted all seven curves of in vitro gH(2) kinetics satisfactorily. The fitted parameters varied between the different in vitro gH(2) curves, therefore allowing description and classification of the curves, and the underlying interpretations were consistent with current knowledge of H-2 production and consumption. In summary, the mathematical model described here provides biologically meaningful parameters to interpret the process of in vitro gH(2) accumulation. Use of this model in future studies with in vitro systems could confirm its wider application to describe gH(2) kinetics when different inhibitors of methane formation are applied. Crown Copyright

Animal Feed Science and Technology, 2012

ABSTRACT Four forage brassicas, kale (Brassica oleracea L. cv. Kestrel), turnip (B. campestris L.... more ABSTRACT Four forage brassicas, kale (Brassica oleracea L. cv. Kestrel), turnip (B. campestris L. cv. Appin), rape (B. napus L. cv. Titan) and swede (B. napus L. cv. Dominion) were compared with perennial ryegrass (Lolium perenne L. cv. mixture of Delish and Banquet) to examine their potential to mitigate CH4 emissions from sheep. Sixty healthy, one-year-old Romney cryptorchids (liveweight 36 ± 1.0 kg) were randomly allocated to 5 groups of 12. The sheep were initially adapted to their diets for 2 wks on paddocks and 1 wk in indoor pens, then fed at 1.5 times their metabolisable energy (ME) maintenance requirement during measurements. Apparent total tract digestibility (n = 5) and ME (n = 5) of brassicas and ryegrass, and rumen fermentation parameters (n = 10) were measured, and CH4 emissions (n = 9) were determined using open circuit respiration chambers. Correlations between nitrate, sulphur, sulphate, glucosinolates and S-methyl cysteine sulphoxide (SMCO) contents of forages and CH4 emissions were determined. Methane emissions/unit feed dry matter intake (g CH4/kg) from sheep were kale 19.8, rape 16.4, swedes 16.9, turnips 20.6 and ryegrass 22.0. Compared with ryegrass, rape and swedes reduced CH4 yield by 23% and 25%, respectively. Total tract digestibilities were higher for brassicas than for ryegrass: 25% higher for DM, organic matter (OM) and crude protein, and 12–16% higher for neutral detergent fibre (aNDF) and acid detergent fibre (ADF). The ME values (MJ/kg DM) were kale 12.7, rape 13.2, swedes 14.1, turnips 12.1 and ryegrass 9.4. Digestibility (P<0.05) and ME (P<0.001) of the forages were correlated to CH4 yield. The correlation coefficients were −0.570 for OM digestibility, −0.505 for NDF digestibility, −0.469 for ADF digestibility and −0.699 for ME. Although the ratio of acetate to propionate in the rumen of sheep fed brassicas was lower than that measured from those fed ryegrass, this ratio was not correlated to CH4 emissions. There were large variations in nitrate, sulphur, sulphate, glucosinolates and SMCO amongst the forage brassicas and ryegrass, but these parameters could not explain reduced CH4 emissions. Feeding brassica forages to sheep reduced emissions/unit DM intake and digestible OM with the reduction being particularly large for forage rape and swedes. Thus these forages may be a viable option for CH4 mitigation from pastoral based sheep production systems. However the mechanisms underlying the reduction need further investigation.This paper is part of the special issue entitled: Plant Bioactive Compounds in Ruminant Agriculture – Impacts and Opportunities, Guest Edited by A.Z.M. Salem and S. López, and Editor for Animal Feed Science and Technology, P.H. Robinson.

Genetic changes in fibre characteristics of perennial ryegrass (Lolium perenne) may enhance degra... more Genetic changes in fibre characteristics of perennial ryegrass (Lolium perenne) may enhance degradability and thereby improve voluntary feed intake and energy availability from ingested grass. Plant breeding and genetic modification (GM) approaches to altering fibre composition have been initiated, with the ultimate objective of developing cultivars with improved fibre degradability. Ryegrass was modified with gene constructs designed to reduce the activity of key genes in lignin biosynthesis, a major component of fibre that impedes digestion. Concurrently, a grass fungal endophyte was manipulated to express enzymes that digest the structural components of grass fibre. Development of new analytical tools have enabled mining of a diverse collection of ryegrass germplasm, and natural variants were identified for both lignin concentration and levels of specific cell wall compounds that were shown to correlate with forage digestion rate. Both conventional breeding and GM strategies may be exploited to improve degradability traits in perennial ryegrass but further development will be required.

Plant Science, 2006

The polysaccharide compositions of cell walls isolated from the laminae and midribs of chicory (c... more The polysaccharide compositions of cell walls isolated from the laminae and midribs of chicory (cv. Grasslands Puna II) leaves were investigated. The walls, which, except for the walls of xylem tracheary elements in vascular bundles, were non-lignified, were fractionated progressively with 50 mM CDTA, 50 mM Na 2 CO 3 , 1 M KOH, 4 M KOH, 4 M KOH + 3.5% H 3 BO 3 , and hot water. Monosaccharide and linkage analyses of the polysaccharides in the walls and wall fractions indicated that the polysaccharides were similar to those in the nonlignified walls of other dicotyledons. However, the proportions of pectic polysaccharides were particularly high (67% of the total wall polysaccharides in the laminae). These included homogalacturonans (50% of the total wall polysaccharides in the laminae) and rhamnogalacturonan-I (RG-I). In contrast, the proportions of cellulose, xyloglucans, heteroxylans and glucomannans were particularly low. The xyloglucans were probably fucogalactoxyloglucans. The wall polysaccharides from the leaf laminae differed from those from the midribs in having higher proportions of homogalacturonans, lower proportions of non-pectic polysaccharides, and RG-I with a higher ratio of galactan to arabinan. #

Scientific reports, 2015

Ruminant livestock are important sources of human food and global greenhouse gas emissions. Feed ... more Ruminant livestock are important sources of human food and global greenhouse gas emissions. Feed degradation and methane formation by ruminants rely on metabolic interactions between rumen microbes and affect ruminant productivity. Rumen and camelid foregut microbial community composition was determined in 742 samples from 32 animal species and 35 countries, to estimate if this was influenced by diet, host species, or geography. Similar bacteria and archaea dominated in nearly all samples, while protozoal communities were more variable. The dominant bacteria are poorly characterised, but the methanogenic archaea are better known and highly conserved across the world. This universality and limited diversity could make it possible to mitigate methane emissions by developing strategies that target the few dominant methanogens. Differences in microbial community compositions were predominantly attributable to diet, with the host being less influential. There were few strong co-occurrenc...

Scientific reports, 2015

Ruminant livestock are important sources of human food and global greenhouse gas emissions. Feed ... more Ruminant livestock are important sources of human food and global greenhouse gas emissions. Feed degradation and methane formation by ruminants rely on metabolic interactions between rumen microbes and affect ruminant productivity. Rumen and camelid foregut microbial community composition was determined in 742 samples from 32 animal species and 35 countries, to estimate if this was influenced by diet, host species, or geography. Similar bacteria and archaea dominated in nearly all samples, while protozoal communities were more variable. The dominant bacteria are poorly characterised, but the methanogenic archaea are better known and highly conserved across the world. This universality and limited diversity could make it possible to mitigate methane emissions by developing strategies that target the few dominant methanogens. Differences in microbial community compositions were predominantly attributable to diet, with the host being less influential. There were few strong co-occurrenc...

Annals of Animal Science, 2015

PLOS ONE, 2015

The objectives of this study were to examine long-term effects of feeding forage rape (Brassica n... more The objectives of this study were to examine long-term effects of feeding forage rape (Brassica napus L.) on methane yields (g methane per kg of feed dry matter intake), and to propose mechanisms that may be responsible for lower emissions from lambs fed forage rape compared to perennial ryegrass (Lolium perenne L.). The lambs were fed fresh winter forage rape or ryegrass as their sole diet for 15 weeks. Methane yields were measured using open circuit respiration chambers, and were 22-30% smaller from forage rape than from ryegrass (averages of 13.6 g versus 19.5 g after 7 weeks, and 17.8 g versus 22.9 g after 15 weeks). The difference therefore persisted consistently for at least 3 months. The smaller methane yields from forage rape were not related to nitrate or sulfate in the feed, which might act as alternative electron acceptors, or to the levels of the potential inhibitors glucosinolates and S-methyl L-cysteine sulfoxide. Ruminal microbial communities in forage rapefed lambs were different from those in ryegrass-fed lambs, with greater proportions of potentially propionate-forming bacteria, and were consistent with less hydrogen and hence less methane being produced during fermentation. The molar proportions of ruminal acetate were smaller and those of propionate were greater in forage rape-fed lambs, consistent with the larger propionate-forming populations and less hydrogen production. Forage rape contained more readily fermentable carbohydrates and less structural carbohydrates than ryegrass, and was more rapidly degraded in the rumen, which might favour this fermentation profile. The ruminal pH was lower in forage rape-fed lambs, which might inhibit methanogenic activity, shifting the rumen fermentation to more propionate and less hydrogen and methane. The significance of these two mechanisms remains to be investigated. The results suggest that forage rape is a potential methane mitigation tool in pastoral-based sheep production systems.

ABSTRACT Perennial ryegrass is the principal component of diets fed to ruminants in New Zealand. ... more ABSTRACT Perennial ryegrass is the principal component of diets fed to ruminants in New Zealand. Selection for ryegrass improvement should incorporate measures relating to feeding value (i.e. quality×intake) for sheep and cattle. This study was designed to measure the variation in characteristics of nutritive value of three ryegrass cultivars harvested at different stages of regrowth. The cultivars were Grasslands Greenstone (Greenstone; tetraploid), Grasslands Samson (Samson; diploid) and Quartet (tetraploid). They were grown as pure swards with leafy regrowth harvested after 2, 3, 4, 5, 6 and 7 weeks for measurement of chemical composition, physical parameters (i.e. shear force and energy required for mincing), degradation kinetics and distribution of constituents between the immediately degradable (A), potentially degradable (B) and undegradable (C) fractions. Analyses showed that age of regrowth resulted in larger differences in composition and degradation kinetics than cultivar, and emphasised the need to harvest material in a similar condition to that grazed by animals. Cultivar differences were best indicated by chemical composition and ratios of crude protein (CP):neutral detergent fibre (aNDF) in the dry matter (DM), the proportion of CP in the ‘A’ fraction as well as degradation of DM in the ‘B’ fraction. The CP:aNDF ratios averaged for the three cultivars at 2, 3, 4, 5, 6, and 7 weeks were 0.82, 0.76, 0.71, 0.55, 0.48 and 0.42, respectively, with averages at weeks 5 and 6 for Greenstone, Samson and Quartet of 0.59, 0.49 and 0.48, respectively. The ratio differed between ages (P

Published reports of CH4 yields as g CH4/kg dry matter (DM) intake suggest that emissions from sh... more Published reports of CH4 yields as g CH4/kg dry matter (DM) intake suggest that emissions from sheep fed fresh forage chicory (Cichorium intybus) are about 30% lower than from those fed fresh ryegrass. In this study, 2 year old wethers (16; 54±3.8kg liveweight) were fed either mature chicory or perennial ryegrass at 1.3 times maintenance metabolisable energy requirements in the

ABSTRACT Forage chicory (Cichorium intybus) has the potential to mitigate methane emissions from ... more ABSTRACT Forage chicory (Cichorium intybus) has the potential to mitigate methane emissions from ruminants. It was reported that the reduction can be up to 30% compared with perennial ryegrass (Lolium perenne). To accurately evaluate the reduction, fresh chicory and perennial ryegrass in the vegetative state were fed to 24 wethers, 8 of which rumen-fistulated, at 1.3 and 2.2 times maintenance metabolisable energy requirements. Dry matter (DM) intake, whole tract apparent digestibility, rumen fermentation parameters and rumen liquid passage rate were measured in metabolism crates, and methane emissions determined using a calorimetric technique. Chemical analyses showed that chicory contained less DM, organic matter (OM), crude protein, neutral detergent fibre (aNDF), acid detergent fibre (ADF), cellulose and hemicellulose, but more hot water-soluble carbohydrate and pectin, than perennial ryegrass. Methane yield (g/kg DM intake) of wethers fed chicory did not differ from that of those fed perennial ryegrass. Yield was lower at the high versus the low feeding level of ryegrass. Apparent digestibility of DM and OM was higher, and aNDF, ADF, hemicellulose and cellulose was lower, in wethers fed chicory versus perennial ryegrass. In situ DM degradation rate of chicory was higher than that of perennial ryegrass. Rumen liquid passage rate was the same for wethers fed the two forages and higher at the high feeding level. The reduction in methane emissions by feeding vegetative chicory to wethers was limited, but increased feeding level reduces methane yields per unit of DM intake.

Journal of the Science of Food and Agriculture, 2007

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Journal of Applied Microbiology, 2008

Aims: Determine the susceptibility of forage chicory (Cichorium intybus L.) to degradation by rum... more Aims: Determine the susceptibility of forage chicory (Cichorium intybus L.) to degradation by ruminal fibrolytic bacteria and measure the effects on cell-wall pectic polysaccharides. Methods and Results: Large segments of fresh forage chicory were degraded in vitro by Lachnospira multiparus and Fibrobacter succinogenes, but not by Ruminococcus flavefaciens or Butyrivibrio hungatei. Cell-wall pectins were degraded extensively (95%) and rapidly by L. multiparus with a simultaneous release of uronic acids and the pectin-derived neutral monosaccharides arabinose, galactose and rhamnose. Fibrobacter succinogenes also degraded cell-wall pectins extensively, but at a slower rate than L. multiparus. Immunofluorescence microscopy using monoclonal antibodies revealed that, after incubation, homogalacturonans with both low and high degrees of methyl esterification were almost completely lost from walls of all cell types and from the middle lamella between cells. Conclusions: Only two of the four ruminal bacteria with pectinolytic activity degraded fresh chicory leaves, and each showed a different pattern of pectin breakdown. Degradation was greatest for F. succinogenes which also had cellulolytic activity. Significance and Impact of the Study: The finding of extensive removal of pectic polysaccharides from the middle lamella and the consequent decrease in particle size may explain the decreased rumination and the increased intake observed in ruminants grazing forage chicory.

Grass and Forage Science, 2012

ABSTRACT Grasses with fast fibre degradation are required by intensive pasture‐based animal produ... more ABSTRACT Grasses with fast fibre degradation are required by intensive pasture‐based animal production systems to maximize intakes and productivity. To select fast‐degrading elite cultivars, a repeatable, rapid and inexpensive screening method should be developed, so large numbers of samples can be evaluated. This study refined the experimental procedure for the in sacco incubation technique using fresh (not dried) perennial ryegrass (Lolium perenne L.). Pre‐ruminal incubation treatment and ratio of forage weight to the surface area of the in sacco bag have been tested to evaluate their effects on ryegrass degradation kinetic parameters in the bovine rumen. The timing of sampling and the number of sampling time points were also examined. Results indicated that warming the bags in water prior to incubation led to a faster dry‐matter (DM) degradation in the first 12 h. If ratio of forage to bag surface area was between 26 and 45 mg DM cm−2, degradation parameters were not affected by bag fill. Sampling between 9 and 12 h was critical for determining degradation rate. From these results, an improved in sacco incubation procedure is recommended for screening of ryegrasses used for cultivar selection. The principles demonstrated here for ryegrass may be applicable to other forages, although the critical sampling times for measuring degradation rate are likely to differ.

animal, 2013

Water-soluble components of feedstuffs are mainly utilized during the early phase of microbial fe... more Water-soluble components of feedstuffs are mainly utilized during the early phase of microbial fermentation, which could be deemed an important determinant of gas production behavior in vitro. Many studies proposed that the fractional rate of degradation (FRD) estimated by fitting gas production curves to mathematical models might be used to characterize the early incubation for in vitro systems. In this study, the mathematical concept of FRD was developed on the basis of the Logistic-Exponential (LE) model, with initial gas volume being zero (LE0). The FRD of the LE0 model exhibits a continuous increase from initial (FRD 0) toward final asymptotic value (FRD F) with longer incubation time. The relationships between the FRD and gas production at incubation times 2, 4, 6, 8, 12 and 24 h were compared for four models, in addition to LE0, Generalization of the Mitscherlich (GM), c th order Michaelis-Menten (MM) and Exponential with a discrete LAG (EXPLAG). A total of 94 in vitro gas curves from four subsets with a wide range of feedstuffs from different laboratories and incubation periods were used for model testing. Results indicated that compared with the GM, MM and EXPLAG models, the FRD of LE0 model consistently had stronger correlations with gas production across the four subsets, especially at incubation times 2, 4, 6, 8 and 12 h. Thus, the LE0 model was deemed to provide a better representation of the early fermentation rates. Furthermore, the FRD 0 also exhibited strong correlations (P < 0.05) with gas production at early incubation times 2, 4, 6 and 8 h across all four subsets. In summary, the FRD of LE0 model provides an alternative to quantify the rate of early stage incubation, and its initial value could be an important starting parameter of rate.

Animal Production Science, 2011

ABSTRACT Fast degrading perennial ryegrass (Lolium perenne L.) is a desirable characteristic to s... more ABSTRACT Fast degrading perennial ryegrass (Lolium perenne L.) is a desirable characteristic to select for because it can result in increased feed intake by grazing ruminants. Sufficient range in genotypic variation of dry matter (DM) degradation kinetics is a prerequisite for selection. To investigate the genotypic variation, 77 perennial ryegrass accessions sourced internationally, grown in autumn in the same conditions and harvested in the vegetative state, were examined using an in sacco technique. From the time course of DM disappearance, soluble fraction ‘A’, potentially degradable fraction ‘B’, indigestible fraction ‘C’ and the degradation rate k of fraction ‘B’ were estimated. The results indicated that a large range in genotypic variation was present in all degradation parameters. Fraction ‘A’ ranged from 0.48 to 0.60, with the highest five accessions being 21% higher than the lowest five. Degradation rate k of fraction ‘B’ ranged from 0.069 to 0.199/h, with the fastest five being 125% higher than the slowest five. There were no strong correlations between degradation parameters and chemical composition. In conclusion, there was considerable genotypic variation in DM degradation kinetics among perennial ryegrass accessions and this presents plant breeders with ample opportunity to select for fast degrading perennial ryegrasses.

Animal Feed Science and Technology, 2013

ABSTRACT Hydrogen (H-2) is produced in the rumen during the microbial fermentation of dietary car... more ABSTRACT Hydrogen (H-2) is produced in the rumen during the microbial fermentation of dietary carbohydrates, and is consumed as an energy source by H-2-using microbes, especially the methane (CH4)-forming methanogens. In vitro fermentation systems are used to study some aspects of rumen activity, and the kinetics of H-2 accumulation in these systems is a balance between H-2 production and consumption. The fate of H-2 produced during fermentation is either as dissolved H-2 in the liquid phase (dH(2)) or H-2 gas (gH(2)). This study proposes a mathematical model of the processes leading to gH(2) accumulation. The gH(2) was mathematically divided into a dissolvable (x) and non-dissolvable (y) gH(2) fractions. The gH(2) in fraction x was assumed to be available to re-dissolve into the liquid phase and therefore could be consumed by H-2-using microbes. The gH(2) in fraction y represents gH(2) that does not re-dissolve into the dH(2) pool, and thus biologically unavailable for the H-2-using microbes. Our model was developed to describe the changes in gH(2) in an in vitro fermentation system, based on gH(2) production and re-solution. Seven very different profiles of in vitro gH(2) curves were selected to demonstrate the applicability of the new model, including gH(2) accumulation profiles from two feeds and three methanogen inhibitors. The three inhibitors reduced CH4 production in different ways: by partial inhibition of methanogens (bromoethane sulphonate), by complete inhibition of methanogens (root of Rheum palmatum), or by acting as a hydrogen sink (nitrate added as NH4NO3). The new model fitted all seven curves of in vitro gH(2) kinetics satisfactorily. The fitted parameters varied between the different in vitro gH(2) curves, therefore allowing description and classification of the curves, and the underlying interpretations were consistent with current knowledge of H-2 production and consumption. In summary, the mathematical model described here provides biologically meaningful parameters to interpret the process of in vitro gH(2) accumulation. Use of this model in future studies with in vitro systems could confirm its wider application to describe gH(2) kinetics when different inhibitors of methane formation are applied. Crown Copyright

Animal Feed Science and Technology, 2012

ABSTRACT Four forage brassicas, kale (Brassica oleracea L. cv. Kestrel), turnip (B. campestris L.... more ABSTRACT Four forage brassicas, kale (Brassica oleracea L. cv. Kestrel), turnip (B. campestris L. cv. Appin), rape (B. napus L. cv. Titan) and swede (B. napus L. cv. Dominion) were compared with perennial ryegrass (Lolium perenne L. cv. mixture of Delish and Banquet) to examine their potential to mitigate CH4 emissions from sheep. Sixty healthy, one-year-old Romney cryptorchids (liveweight 36 ± 1.0 kg) were randomly allocated to 5 groups of 12. The sheep were initially adapted to their diets for 2 wks on paddocks and 1 wk in indoor pens, then fed at 1.5 times their metabolisable energy (ME) maintenance requirement during measurements. Apparent total tract digestibility (n = 5) and ME (n = 5) of brassicas and ryegrass, and rumen fermentation parameters (n = 10) were measured, and CH4 emissions (n = 9) were determined using open circuit respiration chambers. Correlations between nitrate, sulphur, sulphate, glucosinolates and S-methyl cysteine sulphoxide (SMCO) contents of forages and CH4 emissions were determined. Methane emissions/unit feed dry matter intake (g CH4/kg) from sheep were kale 19.8, rape 16.4, swedes 16.9, turnips 20.6 and ryegrass 22.0. Compared with ryegrass, rape and swedes reduced CH4 yield by 23% and 25%, respectively. Total tract digestibilities were higher for brassicas than for ryegrass: 25% higher for DM, organic matter (OM) and crude protein, and 12–16% higher for neutral detergent fibre (aNDF) and acid detergent fibre (ADF). The ME values (MJ/kg DM) were kale 12.7, rape 13.2, swedes 14.1, turnips 12.1 and ryegrass 9.4. Digestibility (P<0.05) and ME (P<0.001) of the forages were correlated to CH4 yield. The correlation coefficients were −0.570 for OM digestibility, −0.505 for NDF digestibility, −0.469 for ADF digestibility and −0.699 for ME. Although the ratio of acetate to propionate in the rumen of sheep fed brassicas was lower than that measured from those fed ryegrass, this ratio was not correlated to CH4 emissions. There were large variations in nitrate, sulphur, sulphate, glucosinolates and SMCO amongst the forage brassicas and ryegrass, but these parameters could not explain reduced CH4 emissions. Feeding brassica forages to sheep reduced emissions/unit DM intake and digestible OM with the reduction being particularly large for forage rape and swedes. Thus these forages may be a viable option for CH4 mitigation from pastoral based sheep production systems. However the mechanisms underlying the reduction need further investigation.This paper is part of the special issue entitled: Plant Bioactive Compounds in Ruminant Agriculture – Impacts and Opportunities, Guest Edited by A.Z.M. Salem and S. López, and Editor for Animal Feed Science and Technology, P.H. Robinson.

Genetic changes in fibre characteristics of perennial ryegrass (Lolium perenne) may enhance degra... more Genetic changes in fibre characteristics of perennial ryegrass (Lolium perenne) may enhance degradability and thereby improve voluntary feed intake and energy availability from ingested grass. Plant breeding and genetic modification (GM) approaches to altering fibre composition have been initiated, with the ultimate objective of developing cultivars with improved fibre degradability. Ryegrass was modified with gene constructs designed to reduce the activity of key genes in lignin biosynthesis, a major component of fibre that impedes digestion. Concurrently, a grass fungal endophyte was manipulated to express enzymes that digest the structural components of grass fibre. Development of new analytical tools have enabled mining of a diverse collection of ryegrass germplasm, and natural variants were identified for both lignin concentration and levels of specific cell wall compounds that were shown to correlate with forage digestion rate. Both conventional breeding and GM strategies may be exploited to improve degradability traits in perennial ryegrass but further development will be required.

Plant Science, 2006

The polysaccharide compositions of cell walls isolated from the laminae and midribs of chicory (c... more The polysaccharide compositions of cell walls isolated from the laminae and midribs of chicory (cv. Grasslands Puna II) leaves were investigated. The walls, which, except for the walls of xylem tracheary elements in vascular bundles, were non-lignified, were fractionated progressively with 50 mM CDTA, 50 mM Na 2 CO 3 , 1 M KOH, 4 M KOH, 4 M KOH + 3.5% H 3 BO 3 , and hot water. Monosaccharide and linkage analyses of the polysaccharides in the walls and wall fractions indicated that the polysaccharides were similar to those in the nonlignified walls of other dicotyledons. However, the proportions of pectic polysaccharides were particularly high (67% of the total wall polysaccharides in the laminae). These included homogalacturonans (50% of the total wall polysaccharides in the laminae) and rhamnogalacturonan-I (RG-I). In contrast, the proportions of cellulose, xyloglucans, heteroxylans and glucomannans were particularly low. The xyloglucans were probably fucogalactoxyloglucans. The wall polysaccharides from the leaf laminae differed from those from the midribs in having higher proportions of homogalacturonans, lower proportions of non-pectic polysaccharides, and RG-I with a higher ratio of galactan to arabinan. #