Does your cow have ’glasses’?

From the magazine Bovilogisk.

If your cows have too low a daily gain, diarrhoea or faded fur around the eyes, this could be a sign of copper deficiency.

A new feeding season has begun and, this year, several farmers have had to prepare a different feeding programme. This is the result of last year’s warm summer, which affects the quantities of roughage and, not least, the quality.

Lately, several farmers have approached Vilofoss with worries about the so-called ”copper glasses” in their cows. They wanted to know the reason for it; and if they gave enough copper to the cows.

Copper is an essential micromineral in cattle; milking cows too. Copper deficiency shows in the form of poor daily gain, diarrhoea, absent pregnancies and a fading coat, with the first signs typically being around the eyes, where the hair coat is thin – the so-called ‘copper glasses’.

Clinical examinations of copper deficiency reveal anaemia (a lack of haemoglobin in the blood), reduced copper concentration in the blood plasma and the liver, and an increased iron accumulation in the liver.

If the amount of molybdenum in the feed for cattle increases, so does the need for supplementing the feed with copper.
According to literature, the minimum safety copper/molybdenum ratio is 2-4 (Underwood, 1976). A low copper concentration combined with a high molybdenum concentration in the roughage (grass silage) often necessitates an extra copper in the mineral mix. A high level of molybdenum in the roughage increases the risk of copper-molybdenum sequestrants, which make the copper inaccessible to the cow.

Therefore, knowing the contribution of roughage is the best starting point for giving the right amount of copper and ensuring absorption. We recommend analysing the minerals in the feed. The results of the mineral analyses of the 2018 grass silage show very large variations in the micromineral concentrations – and, consequently, in the copper and molybdenum concentrations.

The next question is whether there is enough copper accessible in the grass silage, or whether the stressed growing season means a change in accessibility? Depending on the source, cows utilise absorbed copper by 1-5% only, and approx. 60% of the copper in grass silage will be found in the indigestible elements of the plant (Kincaid, 1983). So, in principle, any substantial changes made to the composition of roughage will also result in considerable changes in feed efficiency.

There are several ways of adding extra copper to the mineral mix. Most often, mineral mixes contain copper sulphate, a relatively non-expensive source of copper. The use of copper sulphate, however, depends on the raw material dissolving in the cow’s digestive tract and the copper ion fixing to a transporter, a so-called ligand, for the copper ion to be absorbed via the intestinal wall. If this does not happen, or if a sequestrant is formed – as mentioned above, via e.g. molybdenum – excretion will take place. Using copper sulphate as a source of copper also implies the risk of the copper ion and the sulphur ion once again binding to a copper sulphide bond, which also makes the copper inaccessible to the cow.

Large quantities of copper sulphate have a negative impact on the bacteria in the cow’s rumen. This can be avoided by using organically bound copper sources, where the copper molecule is chemically bound to an amino acid. This considerably increases the chance of the cow absorbing and utilising the copper.





Sources:

Underwood, E.J. 1976: Molybdenum in animal nutrition. Molybdenum in the environment W.R. Chappell and K.K Peterson, ed. Marcel Dekker, Inc., New York, NY

Kincaid, R.L, Blauwiekel, R.M. and Cronrath, J.D. 1986: Supplementation of Copper as Copper Sulfate or Copper Proteinate for Growing Calves Fed Forages Containing Molybdenum. Department of Animal Sciences Washington State University, J. Dairy Sci 69: 160-163

Kincaid, R.L., and Cronrath J.D. 1983: Amounts and distribution of minerals in Washington Forages. J. Dairy Sci. 66: 821