Pyrrolizidine alkaloid poisoning of yaks: identification of the plants involved

Abstract

A search was undertaken in the most eastern part of the Himalayan kingdom of Bhutan for the plants which are causing severe losses of yaks due to pyrrolizidine alkaloid poisoning. Two Senecio and three Ligularia species were found on yak pastures at altitudes between 3000 and 4000 m, including one so far underscribed Ligularia species. None was previously known to contain pyrrolizidine alkaloids. Another Senecio species was found between 2500 and 3000 m, an altitude too low for yaks to be kept but significant for other cattle. The search was supported by field chemical tests for the alkaloids and the diagnosis was later confirmed by thin layer chromatography and high pressure liquid chromatography. Two of the Senecio species had exceptionally high concentrations of pyrrolizidine alkaloids of about 0.5 per cent in the dry matter.

Sympatric Yaks and Plateau Pikas Promote Microbial Diversity and Similarity by the Mutual Utilization of Gut Microbiota

“…Generally, small mammals possess stronger resistance to PSMs than large mammals [ 67 , 68 ], a trait that is derived from the gut microbiota [ 55 ]. However, yaks and other large herbivorous mammals have an extremely weak capacity to cope with poisonous PSMs [ 67 , 68 , 69 ] and, hence, are often poisoned by accidentally foraging poisonous plants [ 70 ]. Therefore, yaks must employ alternative pathways to degrade PSMs, if possible.…”

Pyrrolizidine alkaloid poisoning in yak

“…Walker and Kirkland (1981) also observed that the scarcity of other feed forces cattle to consume Senecio lautus despite its obvious unpalatability. Although five Senecio species were reported in the Bhutan cases, the toxic cases were due to S raphanifolius (Winter and others 1992, 1994). The findings in the present cases of necrotic lesions on the skin, corneal opacity, affection of joints, febrile conditions, nervous symptoms, abortion, premature/still birth and the rectal folding have not been reported in any of the earlier cases of pyrrolizidine poisoning.…”

“…During this period, yaks survive on wilted and frosted grass residues and will eat any green foliage available, including Senecio species. Winter and others (1994) reported Senecio poisoning cases in yaks from Bhutan, stating that the non‐availability of palatable grass and hunger compelled the yaks to graze on poisonous weeds. Walker and Kirkland (1981) also observed that the scarcity of other feed forces cattle to consume Senecio lautus despite its obvious unpalatability.…”

Susceptibility of yak (Bos grunniens) to copper deficiency

“…Winter and others (1992) described severe losses of free‐ranging domestic yak due to pyrrolizidine alkaloid poisoning, and the suspected toxic plants were later identified as Senecio raphanifolius, Senecio biligulatus, Ligularia mortonii, Ligularia amplexicaulis and a then unknown Ligularia species (Winter and others 1994). Apart from pathological changes corresponding to alkaloid poisoning in other species, skin lesions were a consistent and even pathognomonic symptom, although such lesions have not been described in cases of alkaloid poisoning in other animals.…”