Copper is one of a number of micro-minerals required by dairy goats. Even though copper is required in very small amounts in a goat’s diet, both copper deficiency and copper toxicity can occur, often in the presence or non-presence of other minerals. Several key functions of copper are:
- Proper iron metabolism and production of hemoglobin in the blood
- Numerous enzymes needed for growth, reproduction, immunity and the nervous system
- Pigmentation of skin and hair
- Proper hoof growth
- It is a structural component of certain proteins
- Is required by rumen micro-organisms
There are a host of problems that can occur as a result of copper deficiency, some of which are:
- Anemia as a result of reduced iron mobilization
- Spontaneous bone fractures
- Poor hair pigmentation
- Reduced growth
- Reduced Fertility
Copper toxicity can indicated by these symptoms:
- Weight loss
- Depression, weakness, lethargy
To understand the function and availability of copper in goat diets requires an understanding of how elements interact with each other. Since an in-depth study of elemental chemistry is beyond the scope of this article, suffice it to say that all elements are unique in the way they interact or don’t interact with other elements. A well-known elemental combination is salt. Salt is made up of two very reactive elements, sodium and chlorine, both of which are dangerous and poisonous by themselves but, when combined, form a very necessary nutrient. Not all elements, however, combine to form favorable compounds. Cyanide gas is an example of a very bad combination.
Due to similarities in their atomic properties, many elements can compete with other elements in the body. A binding site in an enzyme, for instance, may be fooled into thinking that it’s getting a copper ion when it may really be getting a sulfur ion thus keeping the copper from doing its thing.
Molybdenum reduces copper uptake in a goat’s diet, increases copper excretion and forms an insoluble, useless compound. Low dietary zinc and iron levels and high calcium levels accentuate copper toxicity. Conversely if zinc, iron or sulfur are excessive in a diet, copper will bind to them. Iron and zinc compete with copper for binding sites during absorption in the body. A major key to diagnosing copper deficiencies or toxicities requires knowing what the rest of the diet consists of. A goat owner may be blaming a problem on too little copper, when the real problem might be high molybdenum in a forage or high iron or sulfur in a goat’s water source.
Unfortunately current data on copper requirements for goats is not available. Goats do not exhibit the intolerance to copper like sheep do. Sheep are very susceptible to copper toxicity when dietary copper levels approach or exceed 20 ppm (parts-per-million or milligrams per kilogram). Mineral and vitamin pre-mixes or complete feeds formulated for sheep have no added copper. A feed intended specifically for sheep should not be fed to goats—unless an additional source of copper is supplied to the goat. Most dairy goat breeds weigh about 1/10th of a large-breed dairy cow. Extrapolation of copper requirements for dairy cows places copper requirements at 15 to 20 milligrams per day for goats. Dairy cows have been found to tolerate copper levels of 100 ppm in the diet with no ill effects and even higher levels for short periods of time. Copper accumulates in the liver for a time, and then large quantities are released into the blood-stream, causing a hemolytic crisis associated with jaundice and liver necrosis and, eventually, death. If copper toxicity is suspected, a necropsy of the liver is the best means of finding out. Unless a goat owner is very sure that there are issues with antagonistic elements in the goat’s diet, attempting to put a diet together with excessive levels of copper is irresponsible and would be ill-advised considering the current expense of copper products in recent years. Attempts should be made to correct the other issues before adding copper to a diet.
Forage, which is the foundation for all ruminant diets, is usually very low in copper content. Grass and alfalfa will test from 4 to 10 ppm—a fairly large range. Grasses test lower in copper and alfalfa tests higher. Leaves have more copper than stems so if goats must eat a lot of stemmy grass or hay they will be consuming less copper. A goat whose diet consists solely of forage and eats 3 kilograms (dry matter) per day will be consuming between 12 and 30 milligrams of copper. This may be acceptable depending on the expectations of the goat and how much of any other antagonistic elements may be consumed in that same forage. Iron and sulfur levels are usually low in forages as well. But it’s common for water sources to have high levels of both iron and sulfur which will bind with the copper. Any amount of molybdenum found beyond trace amounts in forages should be cause for concern and the diet should be examined by a nutritional expert. (Note: If a forage analysis comes back with high iron or manganese it means there was a lot of dirt in the sample.)
Goat owners should have their forages tested, especially when making significant changes from one forage to another—for instance changing pastures or a different cutting of hay. They should also have a very good idea of how much dry matter their goats consume in order to know how much copper is being consumed. Dairy goat diets often include a grain mix fortified with vitamins and minerals which nearly always includes added copper.
Copper nutrition is needed for a healthy immune system—but again it doesn’t take much. Copper is needed for proper development of antibodies and white blood cells as well as antioxidant enzyme production. Since goats seem to tolerate copper well, it’s prudent to keep copper levels in breeding, pregnant and lactating does perhaps as high as 40 to 50 ppm. Work closely with a nutritionist when considering elevated levels of dietary copper since there are so many variables that may affect how much should be fed.
When trying to diagnose a copper deficiency, one of the first areas to look at is whether the goat is anemic. Copper works as a catalyst necessary for the absorption of iron into hemoglobin. Since anemia in goats can also be caused by parasites, careful diagnosis is necessary before adding more copper to a diet.
Copper sulfate and copper chloride are the most common sources of added copper in diets. Copper oxide should be avoided since its bio-availability is near zero. There are now several companies marketing chelated (also known as proteinates) forms of copper. These products chemically bind a protein or amino acid to the copper ion which makes the copper more bio-available. (The products can also be known as organic trace minerals.) Some copper chelates are marketed in combination with zinc, manganese and cobalt chelates to ensure a proper balance of all four of these essential minerals. Since copper plays a role in immune function there may be some advantage to including selenium and vitamin-E in diets as well since selenium is deficient in many regions of the U.S. Research on all mineral and vitamin requirements for goats is something that is sorely needed. Copper along with all mineral metabolism in goats is complex. A full understanding of the entire mineral profile in a diet is essential when diagnosing a copper deficiency or toxicity.