Effect of Dietary Extremes on Impala (Aepyceros melampus) Rumen Epimural Flora

The impala, classified as an intermediate feeder among wild ruminants, grazes exclusively on green grasses during the summer rains but turns to an essentially browse habit during the winter, when a diet of leaves, pods, and twigs is supplemented with dried grasses. Scanning electron microscope studies of bacteria attached to the rumen epithelia of animals feeding on digestible, carbohydrate-rich grazing diet showed a high level of surface colonization, with pockets of mixed morphological types occupying spaces vacated by desquamated epithelial cells. Rumen wall colonization in browsing animals on an indigestible, abrasive, low-plane diet showed denudation of distal papillar surfaces with sparse homogeneous adherent flora in the microprotected areas towards the bases. Forage characteristics associated with raised volatile fatty acid concentrations in ingesta, higher rate of epithelial sloughing, and minimum abrasion were interrelated with density and complexity of the adherent bacterial flora.