Selenium poisoning in dairy cattle (abstract)

Authors: Gill JM
Publication: New Zealand Veterinary Journal, Volume 41, Issue 1, pp 46, Mar 1993
Publisher: Taylor and Francis

Animal type: Cattle, Livestock, Production animal, Ruminant
Subject Terms: Clinical pathology, Diagnostic procedures, Mortality/morbidity, Pathology, Selenium, Trace elements, Toxicology
Article class: Abstract

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Abstract: An outbreak of chronic selenium poisoning occurred in a mob of 30 Friesian dairy cows. These cows were all autumn calvers on a well-managed dairy farm.
Of the nine cows affected, four died and five made a slow recovery.
The affected cows showed the initial signs of poisoning in the first week after calving. Anorexia and progressive weight loss was observed in all affected cows. Some cows also showed a watery diarrhoea, dyspnoea, mastitis or ketosis. Death or recovery usually occurred about a month after the initial signs were seen.
One cow killed in extremis was necropsied. Apart from a marked loss of condition, severe lung oedema was noted.
Liver selenium levels (on a wet weight basis) in this cow and another dying the week before were 82,000 nmol/kg and 111,080 nmol/kg respectively.
Blood selenium levels of three affected cows that made a slow recovery ranged from 8,230 to 19,490 nmol/l (after a month of illness) and the mean blood selenium level of 10 clinically normal cows from the affected group was 7,365 nmol/l.
The affected group of cows had been given two selenium pellets in early February and two magnesium bullets about 1 week before the expected calving date. No other source of selenium was identified on the property and barley fed at the time of the outbreak had very low levels of selenium (0.0016 ppm).
It was hypothesised that an electrochemical reaction between the selenium pellets and magnesium bullets may have caused a sudden massive release of selenium from the pellets.
This has yet to be proven.

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