Abstract
Crop residues are often referred to as ‘lignocellulosics’ as they are rich in cellulose which is bound with a biopolymer lignin. Rumen microbiota (bacteria, protozoa and fungi), even with their hydrolytic enzymes, are not very competent enough to break these bonds efficiently. Biological treatment of such crop residues using white rot fungi (WRF) can break the ligno-cellulose complexes, liberating free cellulose and thus enhancing their feeding value for ruminants. Biologically treated roughages have higher digestibility for most of the nutrients (both cell walls and cell solubles) with an increase in crude protein content as compared to untreated material, besides ensuring more fermentable substrates in the rumen. Further, recent studies have indicated low methane emission from feedstuffs subjected to solid state fermentation (SSF) with ligninolytic fungi as a result of their improved digestion and nutrient assimilation. This review primarily deals with the nature and composition of crop residues, their inherent nutritive constraints as ruminant feed and to overcome the same by means of biological treatments. The progresses to date in in vitro and in vivostudies on biologically treated lignocellulosics have also been reviewed. Key words: Crop residues, ligninolytic fungi, ruminant, digestibility, methane.
Highlights
Ruminant animals in many tropical countries subsist mainly on crop residue based diets
A vast energy potential is locked in these lignocellulosic crop residues (Jung, 1989), these are not utilized to their fullest potential for ruminant feeding due to poor digestibility, low nitrogen and mineral contents which rendered them to be classified under non-maintenance type of feeds
The biological treatments of crop residues to improve the accessibility of cellulosic fractions, improving their digestibility and feeding value have been attracting the extensive interests among researchers (Zhang et al, 2007; Yu et al, 2009) this process has a long history
Summary
Rumen microbiota (bacteria, protozoa and fungi), even with their hydrolytic enzymes, are not very competent enough to break these bonds efficiently. Biological treatment of such crop residues using white rot fungi (WRF) can break the ligno-cellulose complexes, liberating free cellulose and enhancing their feeding value for ruminants. Recent studies have indicated low methane emission from feedstuffs subjected to solid state fermentation (SSF) with ligninolytic fungi as a result of their improved digestion and nutrient assimilation. This review primarily deals with the nature and composition of crop residues, their inherent nutritive constraints as ruminant feed and to overcome the same by means of biological treatments.
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