Copper sparks poisoning alert
COPPER poisoning in cattle appears to be on the increase and could be the result of over-enthusiastic use of mineral supplements, believes one expert.
Speaking at the SFT/HGCA meeting held in Coventry last week, Chris Livesey of the Vet Lab Agency warned delegates about a growing copper problem. "Between 1980 and 1999, VLA recorded 34 incidents of bovine copper poisoning, but 33 separate herds were affected between 1999 and 2002."
Of the 33 herds investigated in the last three years, 91% were Holstein Friesian cattle and 9% Jersey, said Mr Livesey. "Incidence in the herds was usually less than 3%. Clinical signs of disease persisted for up to 14 days, but the average duration was two days and recovery was rare."
Typical symptoms of copper poisoning reported by vets to VLA included jaundice, brown mucous membranes, acute milk drop, lack of appetite and red or brown urine, said Mr Livesey.
Worried by the increase in reported cases of copper poisoning, he recorded feed policy of the farms concerned. "On 23 farms, producers were feeding more than 1000mg copper/head a day and this was the cause of copper poisoning. Copper was being provided in concentrates with haphazard additional supplementation and many producers didnt know how much they were supplying. "
The Feedingstuffs Regulations (2000) permit a maximum of 35ppm copper in dairy cow diets – equivalent to 800mg copper/cow a day, explained Mr Livesey.
"Larger amounts of copper can be fed to ruminants, but only on prescription. The Feedingstuffs Regulations limits are well in excess of dairy cow copper requirements, except for cows exposed to high levels of copper antagonists."
Producers should aim for total diet copper levels closer to cow requirements, advised Mr Livesey (see table). "The most common reason given by producers for supplementation was to avoid infertility, but copper status had not been assessed in most affected dairy herds before supplementation. Where high level supplementation is introduced, liver copper concentrations should be monitored to ensure levels are not excessive."
But on 10 farms in the study, there was no evidence of over-supplementation, said Mr Livesey. "It was difficult to tell why cows on these farms had copper poisoning. There may be a genetic influence or diet copper may have been more available to cows."
Although it was unclear why copper poisoning seemed to have increased in recent years, Mr Livesey stressed it was important for producers to be aware of how much they were feeding as it may have implications for milk safety. "Cows with copper poisoning will have higher levels of copper in their milk." Dairy farm assurance schemes could provide a way of monitoring diet copper levels, he suggested. *
Antagonist Diet copper
High case by case.
Antagonists are minerals, such as molybdenum, which interfere with copper metabolism.