COPPER- MOREHARM THANGOOD…?
COPPER toxicity is well recognised in sheep, but fewer are aware that it can also cause death in cattle. Yet recent submissions to the Vet Lab Agency show a significant increase in reporting over the past few years.
Speaking at the British Cattle Veterinary Association conference, Cornelia Bidewell vet investigation officer at Winchester VLA explained how copper poisoning appeared to be increasing.
"Between 1980 and 1999, VLA laboratories recorded a total of 34 incidents of copper poisoning in cattle, but 33 separate herds were affected in the three years from 1999 until 2002."
Typical clinical symptoms for cows with copper poisoning include jaundice, acute milk drop, red/brown urine and chocolate coloured mucous membranes, she explained. "Cows usually died within 2-3 days; those surviving a few days longer were usually culled before death."
Although detailed investigations were carried out for each of the 33 recently affected farms, it was difficult to pin down the cause in every case, said Ms Bidewell. Thirteen herds were receiving no more than 1000mg copper/cow a day, nine were fed between 1001mg and 2200mg/day with one herd feeding 8000mg/day.
"Although 1000mg copper/day is well above the normal requirement for copper, it is considered to be insufficiently high to cause copper poisoning," she said.
However, Chris Livesey of VLA Weybridge, also involved in investigating these cases, is concerned by the level of over-supplementation of copper he believes is happening on some farms. "The feedingstuffs regulations allow a maximum of 35ppm of copper, equivalent to 840mg/day, in dairy cow diets. Larger amounts can be fed to cattle, but only on prescription.
"In this study, nine herds were supplying more than 1000mg copper/cow a day with one farm supplying in excess of 2200mg. This is excessive according to all current recommendations from the US and UK and supplementation was not usually under vet prescription (see panel).
"Feedingstuffs regulation limits are also well in excess of dairy cow copper requirements except for cows exposed to high levels of copper antagonists, such as molybdenum."
On 23 of the 33 affected farms, copper supplements were being fed in addition to copper in purchased concentrates, said Mr Livesey. "The most common reason given for supplementation was avoidance of infertility, but copper status should have been assessed before supplementation.
"The possibility of improving fertility by providing additional copper may have led some producers to supplement unwisely. Investigate other causes of infertility first," he advised.
"Supplementation should only be necessary when cattle have classical copper deficiency or are being exposed to high molybdenum levels. There is no other reason for doing it." *
• Low antagonists 12ppm.
• Mod antagonists 25ppm.
• High antagonists case by
Copper is unlikely to improve fertilty and may do harm, warns Chris Livesey.