Lichen polysaccharides and their relation to reindeer/caribou nutrition

Samples of Cetraria islandica, Cetraria nivalis, Cladina stellaris, Cladina arbuscula Cladina rangiferina and Stereocaulon paschale were collected at 3 sites in 2 mountain areas in Norway. Alectoria ochroleuca was collected a t 3 sites in 1 of the mountain areas. Lichens contained between 83 and 93% fiber, measured by the dietary fiber analysis, with Cladina spp. containing significantly more fiber than the other lichen species. The fiber consiste d mainly of mannose, galactose, and glucose, but the relative content of ea ch monosaccharide differed between species. Fibers from Cetraria spp. and A lectoria ochroleuca contained significantly more glucose than those from Cl adina spp, and Stereocaulon paschale, while Cladina spp. and Stereocaulon p aschale contained significantly more mannose and galactose, The higher gluc ose content in Cetraria spp. and Alectoria ochroleuca was reflected in a hi gh lichenan content in these species, while the Cladina spp. and Stereocaul on paschale contained no lichenan, Solubility of the fiber fraction in hot water was strongly correlated to lichenan content, and great differences ex isted between species. Less than 5% of the dietary fiber was soluble in lic hens of the Cladina genus, while more than 50% of the fiber was soluble in Cetraria islandica and Alectoria ochroleuca. Twenty-one percent of the diet ary fiber was soluble in Cetraria nivalis. In vitro gas production experime nts using rumen inocula from reindeer revealed a higher gas production rate the first 5 hours of incubation in Cetraria islandica, Cetraria nivalis, a nd in Alectoria ochroleuca compared to Cladina spp, and Stereocaulon pascha le, Maximum production rate was observed at about 13 hours and dropped rapi dly thereafter, No systematical differences in gas production rate between lichens species were observed after the initial phase. Differences in gas p roduction rate in the initial phase resulted in higher total gas production in Cetraria islandica, Cetraria nivalis and in Alectoria ochroleuca compar ed to Cladina spp. and Stereocaulon paschale the first 9 hours of incubatio n. Total gas production after 52 hours of incubation did not vary between s pecies. Gas production characteristics indicate that the amount of readily fermentable fraction was greater, whereas the amount slowly fermentable fra ction was lower in lichens of the Cetraria genus and in Alectoria ochroleuc a compared to Cladina spp, and Stereocaulon paschale, The water-soluble fra ction is easy available for rumen micro-organisms and the results indicate a close relationship between high gas production in the initial phase and h igh proportion of water soluble fibers and/or lichenan content. Content, co mposition, and solubility of the fiber fraction could thus be potentially i mportant factors determining nutritive value of the lichen for reindeer/car ibou.