Intoxicação experimental por Brachiaria decumbens em coelhos

Abstract

Brachiaria spp. are fodder that makes up a large part of pasture in Brazil, due to the easy cultivation, good resistance to drought, good adaptation to different soils and low maintenance cost. However, this grass ingestion is related to photosensitization outbreaks, in bovine and ovine, mainly, causing significant economic losses. The hepatotoxic effects related to the grass ingestion are: the crystals formation and foamy macrophages caused by the accumulation of toxic metabolites, leading to changes in the biliary system causing phylloerythrin retention, and consequently the photosensitization with the skin lesions. In bovine and ovine, commonly, it is observed at necropsy different degrees of jaundice and increased liver size with brownish-yellow coloration. On histological observation, hepatic lesions are composed of vacuolization and swelling or individual necrosis of hepatocytes, biliary system, proliferation of ducts and biliary canaliculis, birefringent crystals and isolated foamy macrophages or small clusters. Histological changes, similar to findings in ruminants, were also described in the liver of naturally intoxicated rabbits in B. decumbens pastures, but in experimental replicates it was not possible to reproduce the liver injury. Therefore, the objective in this present study was to evaluate the sensitivity of rabbits as an experimental model for B. decumbens intoxication, by reproduction of hepatic lesions caused by intoxication. Two experiments were carried out, in the first, the animals showed no clinical signs and no macroscopic and microscopic alterations of B. decumbens intoxication. The rabbits of experiment 2 also did not develop clinical signs and macroscopic lesions, however, in histology it was possible to observe foamy macrophages isolated or small clusters in the liver and in mesenteric lymph nodes. When they were submitted to lectin-histochemistry technique, they showed high reactivity for the sWGA, RCA-I, WGA and GSL lectins, thus highlighting the importance of this work, since it showed histopathological lesions by Brachiaria spp in experiments with rabbits, demonstrating that this animal species can be used as an experimental model.