A case of onion poisoning in a cow

There are recorded cases (Cheeke and Shull, 1985) of onion poisoning in cattle and horses that have eaten onions, Allium cepa, but none in New Zealand (Connor, 1977). In this country pigs (Anon, 1978) and a dog (Smith and Ellison, 1986) have been reported as having been poisoned by eating onions. This letter reports a case of poisoning by that plant. A dairy herd of about 160 cows was fed onions daily in conjunction with hay and pasture. Three animals were presented for examination with suspected choking. On examination, one was seen to be dull and depressed. Its rectal temperature was 37°C and its mucous membranes were pallid, with evidence of icterus. The owners had noticed several cows with “very dark urine”, but I did not have the opportunity to examine these. A presumptive diagnosis of onion poisoning was made, and a blood sample was taken. The laboratory examination of the blood sample found….