Responses of bulls to copper supplementation in a record of performance test station.

A Hereford bull from a test station, routinely treated for footrot and not responding, was further examined at the Large Animal Clinic at the Western College of Veterinary Medicine. A slight arthropathy of the right shoulder was radiographically visible. The bull was found to have a marginally low plasma copper level of 0.52 ppm. All bulls in the test station were subsequently sampled for an initial plasma copper determination. At this time 76% of the bulls at the station had plasma copper levels below 0.50 ppm. A mineral mix containing 0.2% copper was added to provide 15 ppm copper in the final ration. All bulls were sampled 28 days later with less than 1% of the bulls showing plasma copper levels below 0.50 ppm.Correlation coefficients between plasma copper levels and average daily gain were +0.067 for the presupplementation period, -0.255 for the supplementation period and -0.085 for the relationship between the change in plasma copper levels and the change in average daily gain. None of these correlations were significant (P > 0.05).During the copper supplementation period plasma copper levels increased for all breeds of bulls studied. However, there was no concomitant improvement in rate of gain by the bulls.