Abstract
The objective of the present study was to evaluate the potential of pressurized hot water extracted hemicellulose fractions from various wood species as feeds for ruminants. In Experiment 1, the fermentability of several hemicellulose extracts was screened using an in vitro gas production method. The samples were extracted from spruce (Picea abies) including mainly galactoglucomannan (GGM), from birch (Betula pendula) consisting mainly of xylan and from larch (Larix sibirica) consisting mainly of arabinogalactan. The GGM and xylan samples were readily fermented by rumen microbes while arabinogalactan was not. Based on the in vitro study, GGM was chosen for an in vivo digestibility trial using sheep, where it was fed at increasing proportions of diet dry matter (0, 47, 94 and 141 g kg-1) in a Latin Square design. The in vivo organic matter digestibility of GGM was relatively low, 0.58, but PHWE extracted hemicellulose has some potential as a feed for ruminants.
Highlights
Wood is the most abundant source of carbohydrates worldwide
In several AG incubations, the gas production remained extended periods at a very low level, which indicates that some kind of adaptation of the microbes might eventually have happened, but the total gas production was still low compared to other hemicellulose extracts
The in vitro gas production technique proved useful in screening the ability of rumen microbes to ferment various hemicellulose extracts produced using the pressurized hot water extraction method
Summary
Wood is the most abundant source of carbohydrates worldwide. The predominant components of wood are cellulose (400 to 450 g kg-1 dry matter [DM]), hemicelluloses (200 to 300 g kg-1 DM) and lignin (200 to 300 g kg-1 DM), which comprise more than 900 g kg-1 DM of wood, the rest consisting of protein, minerals and other components (Sjöström 1993). Ruminants naturally utilize cellulose and hemicelluloses as major components of their diets, they typically originate from grasses (Van Soest 1994). Wild ruminants including moose (Alces alces L.) consume coniferous trees such as Pinus and Picea species, their digestibility is low (Stolter et al 2009). The in vitro digestibility of DM of various tree species was poor with a range from 0.002 to 0.035 (Millett et al 1970). Because of the linkages of lignin to the carbohydrate fractions, some chemical or physical treatment or their combination is needed to improve their digestibility for ruminants (Millett et al 1973). Pressurized hot water extraction (PHWE) is a novel method that can be used to extract hemicelluloses from wood (Leppänen et al 2011)
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