|Serum Cu (μmol/L)|
|Liver Cu (μmol/kg fresh tissue)|
|Serum ferroxidase (IU/L)|
|Pasture Cu (mg/kg DM)|
1. The data for Cu are not as robust as that for Se and Co because they are based on the absence or presence of clinical signs. Most of the studies have been done by feeding sheep and cattle Cu deficient diets containing about 1-2 mg Cu/kg DM and noting the concentrations of Cu in the liver and serum that are associated with a clinical sign, usually ataxia or osteoporosis. The only data on pasture fed sheep and cattle in New Zealand are from the studies of Ira Cunningham published in the 1950s.
2. Liver Cu concentration is the best index of Cu status as the liver is a storage organ for Cu and therefore reflects a deficiency as well as varying Cu intakes.
3. The metabolism of Cu is complex as dietary factors such as Mo, Zn and Fe can interfere with its absorption. In grazing livestock in New Zealand, Mo is the most important. In the presence of Mo, a decrease in Cu status has been associated with poor growth rates in young cattle and a decrease in pregnancy rate in cows. This is the only situation where a low Cu status has been observed to be associated with animal response when cattle are supplemented with Cu.
4. This situation is complex but it could be considered as a molybdenosis and the treatment is to supplement with Cu.