An assessment of the copper status of dairy herds in the Waikato, Taranaki and Northland in spring and the effects of daily supplementation with copper sulphate

Abstract

The copper status of dairy herds in the Waikato, Taranaki and Northland regions between 1 August and 30 September was assessed by copper determinations made on composite sera from ten cows in each herd. Comparisons were made between two major groups categorised as “as received” and “supplemented”. In the latter, the cows received 2.0–6.0 g/day of copper sulphate orally from late gestation to the end of lactation. Mean copper values were determined from pastures in Taranaki and Northland and from pastures from three soil types in the Waikato. The lowest were in Northland (134.3 μmol/kg) and the highest in Taranaki (173.3 μmol/kg). Calculated dietary available copper levels showed the lowest were from pastures grown on organic soils in the Waikato. These soils also had high molybdenum levels. Serum copper values “as received” were lowest in Northland (7.30 μmol/l), and were marginal folr both Taranaki (9.91 μmol/l) and the Waikato (9.93 μmol/l). The levels in “supplemented” herds were considerably higher, i.e. from the Waikato 11.7 μmol/l and from Taranaki 11.5 μmol/l. When liver and serum copper levels from paired samples were compared there was a reasonable correlation (r = 0.64) but the standard deviation approximated the mean liver copper level, i.e. 155 ± 141 μmol/l. (New Zealand Veterinary Journal 38, 98μ101, 1990)