Study of the relation between straw quality and its colonization by rumen micro-organisms

Abstract

SummaryThe relation between the dry-matter degradability (DMD) of different cultivars of barley straw and their colonization by rumen micro-organisms was studied in incubations of straw with the mixed populationin situand with pure cultures of rumen bacteriain vitro.The total attached populationin situwas quantified by particle-associated i glutamate dehydrogenase (GDH) activity, while the cellulolytic population was assessed by bound carboxymethylcellulase (CMCase) activity. CMCase reached a peak between 24 and 36 h incubation, and the peak activity was highly correlated with DMD between 24 ) and 96 h. After 36 h, CMCase activity declined, particularly with the more degradable (varieties. GDH continued to increase after 36 h and had no relation to DMD. The adhesion of pure cultures of both cellulolytic and non-cellulolytic bacteria was measured i turbidimetrically in a 30 min incubation. No relation was found between DMD and the extent of adhesion by any ofRuminococcus flavefaciens, Bacteroides succinogenes,Butyrivibrio fibrisolvensorSelenomonas ruminantium.It was concluded the rate of degradation of straw is not determined by the initial rate of attachment of cellulolytic micro-organisms, but by the way in which colonization subsequently develops after attachment takes place