Intoxicação experimental por Brachiaria decumbens em ovinos confinados

Abstract

Brachiaria decumbens was fed as exclusive source of food to feedlot sheep. Sheep were evaluated in three periods of the year, of 60 days each, regarding their clinical status and was performed collection of blood samples to measure enzymatic activity of gamma glutamyltransferase and aspartate aminotransferase to evaluate their diagnostic importance and usefulness besides the clinical signs, necropsy and histopathology finds in hepatogenous photosensitization Brachiaria related. Out of 24 feedlot sheep, five died in the first period (February-April), four in the second (June-August) and two in the third (October-December). Main clinical signs were anorexia, jaundice, photophobia and two cases of slight dermatitis, besides dehydration, apathy and corneal opacity. Necropsy revealed generalized jaundice, distended gall bladder and liver with evident lobular pattern. The histological changes varied in severity according the time after the beginning of the plant ingestion; they were more significant in the liver and included bilestasis, swelling and vacuolation of hepatocytes, foammy macrophages, bile duct proliferation and mononuclear inflammatory cell infiltration, further crystal negative images were found within cytoplasm of macrophages present inside of hepatic sinusoid and in the periportal space and also optically active refringent crystal in the lumen of bile tubules. These finds are characteristic of hepatogenous photosensitization, mainly by presence of photophobia, even when the sheep did not present photodermatitis. The results of serum biochemistry activity, during the course of poisoning with strong relation between increased gamma glutamyltransferase activity, and lethality. Onset of arising gama glutamyltransferase activity was 11 days, in average, before beginning of clinical signs. Aspartate aminotransferase had increased activity only close to the beginning of clinical signs. Serum biochemistry results of GGT suggest that they are useful for a precocious diagnosis preventing deaths caused by ingestion of B. decumbens. Thirteen sheep didn't show clinical signs despite significant increases on serum enzyme activity, suggesting the existence of tolerant/resistant individuals. The experimental model of feedlot was adequate to study B. decumbens toxicosis in sheep.INDEX TERMS: Brachiaria decumbens, photosensitization, sheep, pathology, feedlot.

Spontaneous poisoning by Brachiaria decumbens in goats

“…animals from herds that have never had contact with the Brachiaria grasses are more susceptible than those created in this pastures (Lemos et al 1996, Oliveira et al 2012.Perhaps this genetic resistance observed in animals raised in Brachiaria pasture is due to reducing of the mechanism of the toxic effect of the plant such as greatermetabolization capacityand degradation of toxic principle ) and adaptation of ruminal microbiota (Albernaz et al 2010). Moreover, it has been proven the existence of individual sensitivity to intoxication (Saturnino et al 2010. For these reasons, explained a relatively small number of animals have been affected by intoxication in this property.…”

Identification of lamb flocks susceptible and resistant against Brachiaria poisoning

“…Although there are circumstantial evidences that genetics play an important role in the resistance to this toxicosis (Riet-Correa et al 2011) and different degrees of individual susceptibility have been demonstrated (Castro et al 2007, Saturnino et al 2010, Faccin et al 2014), up to date there were no reported studies comparing descendants lambs from susceptible and resistant progenitors in relation to Brachiaria spp. poisoning.…”

“…poisoning (Brum et al 2007, Castro et al 2007, Saturnino et al 2010, Albernaz et al 2010, Mustafa et al 2012, Oliveira et al 2012, Faccin et al 2014.…”

“…Affected animals show apathy, anorexia, icterus, skin pruritus, photophobia, serous ocular discharge, subcutaneous edema in the face and ears; in the skin of poorly pigmented areas there are lesions characterized by erythema, hair loss, and crusts. These areas evolve to necrosis and sloughing of patchy areas of affected skin, associated in many cases to deformity of the ears due to scarring of these lesions (Brum et al 2007, Saturnino et al 2010, Albernaz et al 2010, Mustafa et al 2012, Oliveira et al 2012, Faccin et al 2014.…”

“…An alternative measure of control is the identification of animals resistant to the intoxication by Brachiaria spp. (Riet-Correa & Medeiros 2001) since it has already been reported that within one given herd there may be animals with different degrees of susceptibility (Castro et al 2007, Saturnino et al 2010.…”