A veterolegal case of cassava plant toxicity in malabari goats

Abstract

Cassava (Manihot esculenta) plant is a perennial woody shrub belonging to the family Euphorbiaceae originated from South America. It is an annual crop mostly cultivated in the tropical and sub-tropical regions. Cassava plant is considered as one of the most important energy source for humans and animals due to its efficiency in converting solar energy into carbohydrates. Thang et al. (2010) reported that foliage by products of the plant can be used as feed supplements and is a good source of protein for small ruminants. Fresh cassava foliage or cassava hay is also in practice of being fed to ruminants with good results in animals adapted to the consumption of the plant. Cassava foliage is rich in cyanogenic glycosides among which leaves has the higher concentration compared to roots (Bokanga, 1994). The cyanogenic glycosides in cassava are linamarin and lotaustralin, which gets released from leaves following mastication and get transformed to hydrogen cyanide (HCN) by enzymatic action of β-glycosidase or α-hydrocynitrile lyase secreted by gut bacteria. Cyanide is generally considered toxic to animals due to its inherent capacity to bind with iron, manganese and copper ions, which act as functional groups of many active enzymes of cytochrome respiratory chain for ATP production. Cessation of these ions results in energy deprivation (Zagrobelny et al., 2004). The symptoms of acute cassava foliage toxicity include ptyalism, vomiting, excitement, staggering, paralysis, convulsions, coma and death. Symptoms may not be evident in case of chronic exposure to low doses of cyanogenic glycosides. Sheep and goat are highly susceptible to HCN toxicity than monogastric animals due to its rapid hydrolysis by rumen microbes (Kuma, 1992). A case of cassava leaf toxicity confirmed in five goat carcasses is detailed herein.