THE EFFECT OF MIXTURES OF SUN-DRIED TROPICAL SHRUB LEGUMES INTAKE ANDNITROGEN-BALANCE BY SHEEP

A feeding trial with sheep was carried out at the Centro Internacional de Agricultura Tropical (CIAT) in Colombia to investigate the concept of using mixtures of sun-dried tropical shrub legumes to dilute tanni n levels in the diet and improve nitrogen (N) utilisation by ruminants . Intake, digestibility and N retention were measured with animals con suming: low quality grass (Brachiaria dictyoneura) alone; low quality grass supplemented with Cratylia argentea alone (49:51); and grass plu s C. argentea with high tannin Flemingia macrophylla at 2 levels (53:3 7:10; 55:26:19). The 2 diets with F. macrophylla averaged 0.5 and 0.9% extractable condensed tannins. Intake and N retention were not signif icantly affected by legume supplementation, even though apparent N dig estibility was higher when legumes were added. Urinary nitrogen was re duced as F.,nacrophylla increased in the legume mixture, suggesting le ss rumen ammonia losses due to protein protection by condensed tannins . However, with more F. macrophylla in the mixture, there was a reduct ion in dry matter and fibre digestion and an increase in faecal N and faecal N-ADF. These results suggest that, in formulating legume mixtur es to supplement low quality forages, it is important to consider not only tannin levels but also the digestibility of the legumes used.