Kleingrass (Panicum coloratum L.) Poisoning in Sheep

Abstract

Twenty-four lambs grazing pastures of Panicum coloratum developed photosensitization secondary to hepatic dysfunction. Lesions were necrosis of scattered hepatocytes, obstruction of small bile ducts and bile canaliculi by small aggregates of birefringent crystals, and accumulation of birefringent crystals in phagocytes within sinusoids. The number of crystals in livers of affected sheep varied, depending on the amount of time of exposure to toxic plants and severity of hepatic abnormalities. Crystals in the liver were soluble in acidified ethyl alcohol, acetic acid, pyridine, chloral hydrate, and methanol, but not in xylene, petroleum ether, diethyl ether, acetone, water, or cold ethyl alcohol. Crystals were not stained by oil red O. There was necrosis of epithelial cells in renal distal convoluted tubules, papillary muscles of the heart, and the adrenal cortex. Lesions of Panicum coloratum-associated disease are similar to those associated with photosensitization induced by Tribulus terrestris, Agave lecheguilla, and Nolina texana.

Fall Panicum (Panicum dichotomiflorum) Hepatotoxicosis in Horses and Sheep

“…Individual hepatocyte apoptosis was first noted in sheep grazing kleingrass by Bridges et al in 1987, with more acutely and severely affected sheep having scattered necrotic hepatocytes and numerous apparent mitoses. 4 In contrast to previous descriptions of Panicum hepatotoxicosis, microscopic evaluation of liver specimens in this study did not identify bile crystals. Differences in tissue processing techniques conceivably could account for this difference.…”

“…1 However, several reports document hepatogenous photosensitization or hepatopathies in grazing animals after ingestion of various Panicum, 2-6 Brachiaria, 7,8 Tribulus, 9,10 and Narthecium 11 grass species. These plants contain steroidal saponins, 4,8,[10][11][12][13][14][15] and affected ruminants often develop bile crystals composed of the calcium salts of steroidal saponin glucuronides. [16][17][18][19][20] Only 2 reports 6,15 describe hepatotoxicosis in horses after consumption of these grass species.…”

“…The first outbreak 6 involved Panicum coloratum (kleingrass), a species introduced to Texas in 1952 from Kimberly, Union of South Africa, and subsequently widely planted in the state. 3,4 The second involved Panicum virgatum L (switchgrass) and occurred in eastern Nebraska. 15 Anecdotally, 2 other occurrences of hepatotoxicosis in horses have been observed in the Virginia-Maryland region over the past 15 years (TJD, a conversation, January 2005).…”

Estudos histológico, histoquímico e ultra-estrutural de fígados e linfonodos de bovinos com presença de macrófagos espumosos ("foam cells")

“…A imagem negativa das estruturas cristalóides indica que estas foram dissolvidas com solventes usados no processamento das amostras tanto em microscopia ótica como eletrônica; possivelmente por solventes orgânicos usados no processamento das amostras. As alterações encontradas através dos exames histológico e ultra-estrutural deste estudo são semelhantes às descritas por aqueles autores para casos de fotossensibilização com Panicum coloratum (Bridges et al 1987). A ausência de fotossensibilização nos animais do presente estudo pode ser devido a uma menor intensidade das lesões hepáticas.…”

“…A eliminação dos cristais através da bile é confirmada pela presença de sapogeninas esteróides isoladas a partir de cristais contidos na bile de ovinos intoxicados por Panicum dichotomiflorum (Holland et al 1991). A estrutura dos cristais é a mesma das chamadas fendas de colesterol (Bridges et al 1987). Essas alterações histológicas são atualmente atribuídas à constituintes do próprio capim denominados de sapogeninas esteróides contidas em Panicum sp.…”