The first trial reported is summarized in Table I and was carried out on cows grazing pasture known to produce both copper and selenium de- (6) 1 52(8) 1 88(8) 288 (2) 0 (10) 69(6) ts2 (4) 188 (8)
Balance studies were carried out on four Suffolk-cross lambs which were fed a diet containing only 1.2 mg zinc/kg dry matter; zinc deficiency was induced within three weeks. After a period during which the deficiency was relieved by a pica, the zinc deficient state was re-established. Each sheep was then treated with a soluble glass bolus containing zinc, cobalt and selenium. The plasma zinc concentration of the sheep rapidly increased and was maintained for between six and 10 weeks. The bolus was able to supply the daily requirement of the sheep for zinc, with no detrimental effect on their copper status.
Signs of clinical copper deficiency in ruminant animals include infertility. Blood copper concentrations alone are not an adequate indicator of copper status, as they take no account of the thiomolybdate challenge to the animal. The use of the ratio of caeruloplasmin activity to plasma copper concentration should provide a better indicator of molybdenum induced copper problems. The objectives of this study were to obtain veterinary feedback on the University of Leeds Trace Element Laboratory's (ULTEL) assessment of copper status and responses to any recommended supplementation. Blood samples from 713 female cattle from 114 herds were assessed for copper status, including plasma copper concentrations, serum caeruloplasmin activities and the ratio between the caeruloplasmin and plasma copper (CP/PlCu ratio). On the basis of only plasma copper analysis 95.0 % of the cattle were classified as being of normal copper status using Veterinary Laboratory Agency reference ranges. However, when the CP/PlCu ratio was also considered only 35.6 % of the cattle would be classed as having normal copper status. Appropriate copper supplementation would be required by 30.7 % of the cattle and a further 27.8 % could also benefit from additional copper. Veterinary responses to a questionnaire (80 % returned) indicated that infertility was a major problem in their clients’ herds. Where copper supplementation was recommended and administered an increase infertility was observed. In herds showing poor or lack ofoestrous behaviour/ later embryo loss (signs of clinical copper deficiency), 91.7 % reported that these signs were reduced by copper supplementation. The relevance of the CP/PlCu ratio as a diagnostic aid in the identification of copper responsive infertility has been supported by the responses of the veterinary surgeons.
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