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  • Title: Rates of change in liver copper concentration in cattle given a copper-deficient diet, with or without pre-treatment with tetrathiomolybdate, for evaluation of two parenteral copper supplements.
    Author: Suttle NF.
    Journal: N Z Vet J; 2013 May; 61(3):154-8. PubMed ID: 23013209.
    Abstract:
    AIM: To minimise the impact of initial variation in liver copper (Cu) on assessments of Cu supplements for cattle in depletion/repletion experiments. METHODS: Efficacy of two Cu injections was assessed with 18 calves, weighing 200-250 kg, given a Cu-deficient barley diet, containing 4.1 mg Cu/kg dry matter (DM) and added molybdenum (3 mg/kg) and sulphur (3 g/kg). Initial liver biopsy Cu ranged from 3.15-14.17 mmol/kg DM and nine calves with the highest values were given three subcutaneous injections of 235 mg tetrathiomolybdate (TTM) after 42-46 days depletion to lower liver Cu. Untreated (L) and TTM-treated (H) calves were ranked separately for liver Cu after 50 days depletion and allocated to one of three treatments: 100 mg Cu given subcutaneously as CuCaEDTA in either a paraffin (CuP) or aqueous base (CuA) after 56 days depletion (Day 0) or no injection (O). Thereafter, plasma and liver biopsy Cu were measured every 2-4 weeks for 16 weeks. Responses in liver Cu to Cu injections were compared with and without loge transformation and by linear regression. RESULTS: Prior to Cu injection, the fractional decline in liver Cu concentration (FDLCu) after 50 days depletion was 0.64 (SE 0.066) and 0.80 (SE 0.090) in H and L calves, respectively (p=0.09) and mean liver Cu did not differ on Day -6 (6.65 (SE 0.516) and 4.91 (SE 0.681) mmol/kg DM, respectively). Mean plasma Cu was higher in H than L calves on Day 0 (16.6 (SE 0.52) and 13.3 (SE 0.49) μmol/L, respectively (p<0.001)). Rates of decline in loge liver Cu between Days 0-84 in treatments L and H were: 0.0138 and 0.0071 for Groups O; 0.0033 and 0.0016 for Groups CuP; 0.0073 and 0.0049 for Groups CuA (pooled SE 0.0014) mmol/kg DM/day, respectively. Between Days 84-114, FDLCu was uniformly high across experiments and groups (0.59 (SE 0.042)). Cu injections did not affect plasma Cu, which remained 3.1 (SE 0.41) umol/L higher in Experiment H than in L (p=0.017). CONCLUSIONS: The use of rates of change in liver copper concentrations improved the assessment of efficacy for two parental copper supplements and that of pre-treatment with tetrathiomolybdate, which, contrary to expectation, slowed Cu turnover by mechanisms that remain unclear.
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