Poisoning of cattle by Senecio spp. in Brazil: a review

Abstract

Poisoning of cattle by plants of the Senecio genus represents an important cause of death in cattle and has important economic repercussions in southern Brazil. This review is intended to provide a detailed review of Senecio spp. intoxication in cattle and addresses issues regarding the toxic principle and pathogenesis of the disease caused by these plants and the epidemiology, clinical signs, diagnosis, control and prophylaxis of the disease. Senecio brasiliensis is the main species associated with natural intoxication of livestock in Brazil, and the number of cases associated with the ingestion of S. madagascariensis is increasing. The toxic principle of Senecio spp. comprises the hepatotoxic alkaloids of the pyrrolizidine group (pyrrolizidine alkaloids, PAs). The resulting liver lesions are chronic and irreversible and result from the inhibition of hepatocellular mitosis. Deaths of adult cattle may occur both sporadically and in larger outbreaks over an extended period of time. In cattle raising, Senecio spp. are consumed mainly during the winter, when there is a dearth of forage; at this time the poisonous Senecio species are budding and contain high concentrations of PAs. Spontaneous Senecio spp. intoxication in cattle is a chronic condition that frequently involves acute clinical manifestations. Affected cattle may present ascites, emaciation, intermittent dark diarrhea, tenesmus, rectal prolapse, and neurological signs resulting from hepatic encephalopathy. Hepatogenous photosensitization may be observed but is uncommon. Necropsy findings include dependent subcutaneous edema, ascites, and edema of the mesentery, abomasal folds, and gallbladder. The liver is firm, normal or reduced in size with a white, thick capsule. Microscopically, the hallmarks of Senecio-associated disease are varying degrees of hepatocellular megalocytosis, bile duct hyperplasia and fibrosis. Sheep are significantly more resistant to Senecio intoxication than are cattle and avidly ingest Senecio plants; therefore, the use of sheep for grazing infested pasture is recommended for preventing the associated disease in cattle.

Causes of death of beef cattle raised in feedlots

“…poisoning was the second cause of death in feedlots for finishing. Intoxication by this species is one of the most important causes of death in cattle reared in the field in the southern region of Rio Grande do Sul and mainly affects animals older than 18 months (Grecco et al 2010, Panziera et al 2018). In the feedlots for finishing, cattle were older than 18 months and came from this region; thus, cases of intoxication were expected.…”

Adaptive changes of farmers to the continued invasion of Senecio madagascariensis Poir. (fireweed) in pasture-based systems

“…Given the continuing high percentage of respondents overall who attempt to control reweed (76% of those who had it on their farm in 2011), it evidently remains an important weed of grazed pastures throughout its Australian distribution. This is also re ected in its continued importance to livestock enterprise managers in key areas of reweed distribution in places such as South America (Villalba & Fernández 2007, Bandarra et al 2012, Panziera et al 2018.…”

Plants causing poisoning outbreaks of livestock in South America: A review

“…Senecio (Asteraceae) is the genus most often associated with outbreaks in cattle. In Brazil, it is the most important poisonous plant for cattle in the state of Rio Grande do Sul (Southern Brazil); species related to outbreaks include Senecio brasiliensis , Senecio selloi , Senecio cisplatinus , Senecio heterotrichius , Senecio oxyphyllus , Senecio madagascariensis, and Senecio tweedei ( Panziera et al, 2018 ). In Uruguay, there are cases of poisoning by S. brasiliensis , S. selloi , S. oxyphyllus , S. madagascariensis , and Senecio grisebachii ( Rivero et al, 2011a ), and in Argentina by S. tweediei , S. selloi , S. grisebachii , S. madagascariensis , Senecio pampeanus ( Odriozola, 2011 ), and S. brasiliensis .…”

“…In Chile, several species of Senecio occurred, but only Senecio erraticus has been associated with poisoning ( Araya, 2009 ). S. brasiliensis is the most important toxic species in southern Brazil and Uruguay, but S. madagascariensis , despite being less toxic, is a critical invasive weed introduced in the region in the 1990s with great dispersal capacity that allows it to remain throughout the year in pastures ( Panziera et al, 2018 ).…”

“…The disease mainly affects cattle ( Panziera et al, 2018 ) but also horses from southern Brazil ( Panziera et al, 2017 ), Uruguay ( Rivero et al, 2011a ), Argentina ( Micheloud et al, 2017a ), and Chile ( Araya, 2009 ). Significant outbreaks have been diagnosed in horses, with 20–25% mortality associated with the consumption of S. rudbeckiaefolius , S. madagascariensis , and S. hieronymi in Northwest Argentina ( Micheloud et al, 2017a ).…”