ORIGINAL ARTICLE Degradation of forage chicory by ruminal fibrolytic bacteria X.Z. Sun 1,2 , K.N. Joblin 2 , I.G. Andrew 3 , S.O. Hoskin 1,2 and P.J. Harris 4 1 Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand 2 AgResearch Grasslands, Palmerston North, New Zealand 3 Institute of Natural Resources, Massey University, Palmerston North, New Zealand 4 School of Biological Sciences, The University of Auckland, Auckland, New Zealand Introduction Forage chicory (Cichorium intybus L.) is a plant increasi- ngly being used for grazing ruminants because it provides a high quantity of herbage, particularly during summer conditions (Barry 1998). Forage chicory has a high volun- tary feed intake by animals, is more digestible and results in better animal performance than perennial ryegrass (Lolium perenne L.)-based pasture (Hoskin et al. 1995; Kusmartono et al. 1996, 1997; Foster et al. 2002; Neel et al. 2002). Measurements from grazing deer found that they spent much less time ruminating chicory than perennial ryegrass, with 50% of the animals not rumina- ting at all on chicory (Kusmartono et al. 1996). Indoor experiments showed that although deer spent similar times eating chicory and perennial ryegrass, a much shorter time (33 min per 24 h vs 270 min per 24 h) was spent ruminating chicory (Hoskin et al. 1995). This sug- gests that for chicory digestion, breakdown in the rumen is more important than comminution during chewing. The polysaccharide compositions of the cell walls of forage chicory are similar to those of primary cell walls of other eudicotyledonous forages although their pectin con- tent is higher (Sun et al. 2006). Pectic polysaccharides account for 67% of the cell-wall polysaccharides in chic- ory leaf laminae and 59% of the cell-wall polysaccharides in leaf midribs. Pectins have a domain structure with the most common domain being homogalacturonan (HG) composed of (1 fi 4)-a-d-galacturonic acid residues which may be methyl esterified, together with smaller Keywords Butyrivibrio hungatei, cell walls, Fibrobacter succinogenes, forage chicory, Lachnospira multiparus, pectin degradation, ruminal bacteria, Ruminococcus flavefaciens. Correspondence Keith Joblin, Grasslands Research Centre, AgResearch, Private Bag 11008, Palmerston North 4442, New Zealand. E-mail: keith.joblin@xtra.co.nz 2008 ⁄ 0083: received 15 January 2008, revised 11 March 2008 and accepted 23 March 2008 doi:10.1111/j.1365-2672.2008.03861.x Abstract 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 arabi- nose, galactose and rhamnose. Fibrobacter succinogenes also degraded cell-wall pectins extensively, but at a slower rate than L. multiparus. Immunofluores- cence 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 cellulo- lytic activity. Significance and Impact of the Study: The finding of extensive removal of pec- tic 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. Journal of Applied Microbiology ISSN 1364-5072 1286 Journal compilation ª 2008 The Society for Applied Microbiology, Journal of Applied Microbiology 105 (2008) 1286–1297 ª 2008 The Authors