Abstract
The influence of different copper and zinc contents in rations on blood serum concentrations in dependence on feeding (Groups A and B) and lactation (Lactation 1 and 2) was tested in a feeding trial with 60 German Holstein cows. All animals received a diet based on maize and grass silage ad libitum. 30 cows received a concentrate supplemented with copper and zinc as recommended (Group A), whereas the other 30 animals were offered a concentrate with roughly double the amount of copper and zinc (Group B). Blood samples were taken several times during the lactation to analyse serum concentrations of copper and zinc. Copper serum concentration was influenced neither by the different feeding (11.7 μmol/L in Group A and 12.3 μmol/L in Group B) nor by the lactation (12.0 μmol/L in Lactation 1 and 12.1 μmol/L in Lactation 2). Zinc serum concentration was significantly influenced as well as by feeding (14.1 μmol/L in Group B and 12.5 μmol/L in Group A) and lactation (14.2 μmol/L in the second lactation and 12.8 μmol/L for first lactating cows). For an exact diagnosis of trace element supply, blood serum is a not qualified indicator; other sources (feedstuffs, liver, hair) must also be investigated.
Highlights
Copper and zinc are essential trace elements and they are involved in many physiological processes in animals [1,2,3,4]
What are the reasons for these discrepancies—are serum samples not qualified for diagnosing trace element supply or must the reference values be adapted to actual feeding conditions? The aim of the Veterinary Medicine International
The higher copper and zinc supply in Group B resulted in a mean dry matter intake of 17.4 ± 3.2 kg/d, which is not significantly different from the mean DM-intake of the animals in Group A (17.3 ± 3.3 kg/d)
Summary
Copper and zinc are essential trace elements and they are involved in many physiological processes in animals [1,2,3,4]. The measured trace element concentrations are compared with so-called reference values to characterise the trace element supply and the status of the animals (deficient, sufficient, overdosed). Such a reference value is defined as a quantitative parameter, which is derived under exactly defined conditions from a group of adequately characterized probands with a definite mathematical-statistical method [5]. In the last ten years, there is an increasing reporting in veterinary practice about a “trace element deficiency without clinical signs” diagnosed only by serum trace element concentrations below the applied reference values. What are the reasons for these discrepancies—are serum samples not qualified for diagnosing trace element supply or must the reference values be adapted to actual feeding conditions? What are the reasons for these discrepancies—are serum samples not qualified for diagnosing trace element supply or must the reference values be adapted to actual feeding conditions? The aim of the Veterinary Medicine International
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