THE ROLE OF LEGUME FORAGES AS SUPPLEMENTS TO LOW-QUALITY ROUGHAGES - ILRI EXPERIENCE

Supplementation of basal diets with multipurpose trees (MPTs) increase s essential nutrients available to rumen microbes, increases rate of p assage of particulate matter by 23-53% and of liquid matter by 9-43%. Supplementing teff straw with graded levels of cowpea or lablab signif icantly increased microbial N supply in calves. Supplements of Sesbani a and Chamaecytisus sp, promoted higher N retention compared with unsu pplemented roughage. The ILRI's work on evaluation of MPTs demonstrate d that type, form and quantity affect microbe-MPT interactions and, co nsequently, the utilization of the basal diet. Using gas production as an index of fermentation, it was shown that Chamaecytisus palmensis ( Tagasaste) is fermented rapidly while Acacia angustissima is fermented slowly by mixed ruminal microbes. Volatile fatty acid (VFA) analysis showed that mixed ruminal microbes produced most (63.9 mu mol/ml) VFAs from Sesbania sesban while A. angustissima fermentation produced the least (15 mu mol/ml) amount at 12 h. Extracts of A. angustissima inhib ited the growth of pure cultures of rumen bacteria (Ruminococcus albus , Ruminococcus flavefaciens, Prevotella ruminicola and Streptococcus b ovis). Multipurpose trees affect protozoal populations in sheep differ ently. Sesbania sesban significantly (P < 0.04) increased while Acacia cynophylla decreased the numbers of protozoa in Ethiopian highland sh eep fed a basal diet of maize stover supplemented with various MPTs. M ilk production and growth responses of cattle supplemented with MPTs o r browses were variable. (C) 1997 Elsevier Science B.V.