Estudo sobre a sensibilidade dos caprinos à toxidez de crotalárias tóxicas para bovinos, visando a sua utilização na profilaxia

Abstract

Plant poisoning of farm animals in Brazil is known to be one of the most important causes of death. As there are not many possibilities for treatment of those cases, all efforts must focus on the application of alternative prophylactic measures, among them the use of a less sensitive animal species in areas of the occurrence of certain plants. This study aimed to ascertain the sensibility of goats to crotalarias (Crotalaria spectabilis and Crotalaria juncea), so that this animal species could be used as a prophylactic measure against those plants poisonous for cattle. In order to perform the experiments, 8 young adult goats of both sexes were used, which were randomly divided into two groups of 4 goats, e.g. one group for each plant. None of the 4 goats that received single or daily doses of Crotalaria juncea seeds, developed clinical signs of poisoning or showed changes in the biochemistry examinations, except one goat that exhibited an isolated rise in the levels of alkaline phosphatase. Out of the 4 goats that received single or daily doses of Crotalaria spectabilis seeds, three died. Among these, only the goat that received a 10g/kg single dose of the seeds survived and did not show any clinical sign or biochemical changes during the experiment. The goat that received a 20g/kg single dose of seeds died two days after the intake and exhibited loss of appetite, apathy and ruminal hypotonia. Postmortem and histopathological examination revealed marked centrilobular hemorrhagic necrosis. The goat that received daily doses of 2g/kg of Crotalaria spectabilis seeds for 35 days and died 58 days after the beginning of the experiment showed clinical signs of apathy, anorexia and a growing respiratory distress, besides the yellowish color of the blood serum. At histopathology the main lesion was interstitial pneumonia. This goat exhibited transient changes in the liver of AST, ALP, GGT, total protein, and direct and indirect bilirubin. The goat that received daily doses of 2g/kg of seeds for 150 days was euthanized in extremis. The clinical profile was loss of appetite, progressive emaciation, apathy, ruminal hypotonia and yellowish discoloration of mucous membranes and blood serum. At postmortem and histopathological examination, there was prevalence of the hepatic lesion. The most important microscopic lesions were megalocytosis and bizarre appearance of liver cells and epithelial cells of kidney tubules. Biochemistry showed transient changes in the activity of AST, ALT, ALP, GGT, total protein, urea and direct and indirect bilirubin levels. The results of the present study showed that goats are not indicated to be used as a prophylactic measure against poisoning by Crotalaria spectabilis, but can be recommended as an animal species to graze in areas invaded by Crotalaria juncea for the prevention of poisoning.