Back from The Vet: Mineral Intake in Goats
What minerals do your goats need, and what are the signs of deficiency and overdose?
Reading Time: 7 minutes
If you have spent any time perusing your local feed store, then you are well versed in the multitude of available mineral supplements made for goats and other livestock. These supplements come in all forms, from blocks and tubs to loose and pelleted. They are made for goats of all stages, and even targeted to improve performance. With all of these choices, it is difficult to know what supplement will work best for your herd. Understanding where these minerals are found in common feedstuffs, and what their toxicity or deficiency may cause, is helpful for choosing the right mineral supplement for your farm. In these winter months, when forage may be scarce, offering the appropriate mineral supplement can greatly improve herd health.
Minerals can be divided into two categories: macrominerals and microminerals. Macrominerals are present at a larger amount in the body, and thus the diet. Microminerals, or trace minerals, are found in much smaller amounts. The macrominerals include calcium, phosphorus, magnesium, potassium, sodium, and chlorine. The microminerals of most importance are iron, iodine, zinc, copper, and selenium. Goats have different macro and micromineral requirements than other ruminant species. When selecting a mineral supplement for your herd, choosing one made specifically for goats will be best at meeting the needs of your animals.
Appropriate calcium intake is imperative for good health. It is necessary for growth, as well as for good milk production. Calcium is found in higher concentrations in plants of the legume family, such as alfalfa and clover. Non-dairy goats are generally able to meet their calcium requirements through grazing or consumption of good quality hay. Heavily lactating animals, however, require much more calcium, as it is excreted in milk. These animals also tend to consume more grains, or concentrates, which are generally lower in calcium than forages. Calcium intake can be increased with an increase in alfalfa intake or the addition of a mineral supplement such as dicalcium phosphate. Deficiency in calcium can cause decreased milk production in lactating does. Low calcium can also cause milk fever. Milk fever is a sudden decrease in blood calcium levels associated with kidding or early lactation. While the treatment for this is intravenous calcium and fluid support, prevention is not just the addition of calcium to the diet. In fact, heavily pregnant goats fed a high calcium diet are more likely to develop milk fever, as their body is less capable of mobilizing calcium stores from the bone. Heavily pregnant does should rather be fed a quality forage, such as grass or grass alfalfa mix prior to kidding. This lower calcium diet increases their ability to mobilize calcium stores. After kidding, improving calcium intake can provide increased milk production, especially in dairy goats.
Abnormalities in the intake of phosphorus can have severe ramifications, either when too high or too low. Higher concentrations of phosphorus are found in cereal grains, like wheat and oats. Goats with a deficiency in phosphorus intake show ill-thrift. This can be exhibited by poor rate of growth, poor hair coat, and decreased fertility. Goats with low phosphorous can also show pica, the abnormal ingestion of items like sticks and rocks. Elevated phosphorus intake can cause urethral stones and obstruction. This occurs particularly in male goats, as they have a long, small-diameter urethra. Phosphorous content of the diet should be managed carefully in conjunction with the calcium content. The ratio of calcium to phosphorous should be maintained around 1.5-2:1. Causes for increased phosphorous content include high grain intake and forages fertilized with a high phosphorous fertilizer like chicken litter. When buying hay, it is important to know what fertilizing products were utilized.
Magnesium is another mineral found in high concentrations in legumes. Lack of magnesium intake can result in a condition called grass tetany. This condition, though more common in sheep and cattle, can also occur in goats. In grazing animals, this often occurs in the spring, during times of rapid grass growth, resulting in lower levels of magnesium in the plant. Lactating adult animals are most affected. Some areas with high soil concentrations of potassium and nitrogen can also increase the risk of hypomagnesemia. Animals show signs of sudden convulsions, muscle spasms, and death. This condition is treated with intravenous mineral supplementation. Providing appropriate mineral supplementation is most helpful in preventing grass tetany, especially during times of increased risk.
Potassium is not only a macromineral but is also considered an electrolyte. It is found in higher concentrations in forages and is low in cereal grains. As goat diets are generally high in forage, deficiencies are rare. Animals fed high-grain diets can result in lower intake levels. Animals experiencing diarrhea also tend to have low potassium, in addition to sodium and chloride. Prolonged low potassium levels can yield poor appetite and even contribute to the formation of urinary calculi, while elevated levels may be associated with hypocalcemia in lactating goats.
Sodium chloride, or salt, provides two primary macrominerals. Salt is generally not high in concentration in most forages, though legumes tend to have higher levels than others. It is frequently used as a carrier to ensure the intake of other minerals, as goats have the drive to consume it. Unlike other species, goats have a tendency to eat salt at increased amounts when offered free choice, which — though not harmful — can sometimes result in depressed appetite. Low sodium in the diet can result in decreased growth and also pica.
The micro or trace mineral iron is found readily in forages. Grazing goats rarely have deficiencies. Animals, especially young kids, reared in confinement should be offered iron within a mineral supplement, as they can be more prone to deficiency. Heavily parasitized animals may also suffer from iron deficiency.
Just as in people, deficiency in iodine can result in severe disease. Iodine is deficient in certain soil areas. In the United States, this includes the mountainous West and Great Lakes regions. When buying feed from those regions, testing or supplementation is encouraged. Iodine is supplemented by addition to salt, or in complete mineral supplements. Deficiency in iodine leads to the inability of the thyroid gland to function and produce its hormone. The thyroid hormone is responsible for the control of metabolism. In deficiency, the thyroid gland can enlarge, creating a goiter, or swelling in the neck. Animals can also show signs of poor growth, decreased milk production, and reproductive difficulties — such as retained placentas. Grazing animals, even those being supplemented with iodine, can also suffer deficiency by consumption of goitrogenic plants. Among these plants are soybeans, kale, cabbage, and turnips. These plants inhibit the thyroid’s ability to function, as in iodine deficiency.
The trace mineral zinc is essential for skin growth, as well as male reproduction. Zinc is found in higher levels in cereal grains, rather than forages. Animals suffering from deficiency have dry, flakey skin with poor hair coat and coat growth. Intact male animals show decreased reproductive abilities with smaller testicles and low sexual drive. Some goats also exhibit a condition referred to as zinc responsive dermatosis. These animals show signs of zinc deficiency even when fed mineral supplement with zinc. This is assumed to be an inherited condition in which affected animals do not appropriately absorb dietary zinc and require supplementation at increased levels. When supplemented appropriately these goats return to normal.
Copper is a trace mineral of great importance in small ruminants. It is responsible for the health of red blood cells, as well as the immune system and nerve function. Copper is found in varying levels in the soil. Copper must be managed in relation to molybdenum, as increases in molybdenum prevent the absorption of dietary copper. It is imperative to understand the soil in your area to ensure appropriate supplementation. Deficiencies in copper can result in poor overall health, with anemia, faded hair coats, and even diarrhea. Small ruminants require very small amounts of copper. While goats are less sensitive to copper toxicity than are sheep, they are still at greater risk than other livestock. Copper toxicity can be indicated by abortion, jaundice, weakness, red urine, and pale gums. It generally occurs when goats consume mineral supplements or complete feeds made for other species, such as cattle or swine. Animals suffering from liver disease are also at increased risk of toxicity, as copper is stored in the liver, and is released during disease. Copper toxicity is a serious condition that often results in death.
Selenium is another trace mineral found in varying amounts in the soil. It too can be over- or under-supplemented easily, as its supplemental range is small. Selenium works closely with vitamin E within the body, and when assessing for deficiency, they must be managed together. Deficiency of selenium leads to poor growth, reproductive ill-health — retained placentas and metritis, and in young kids a condition known as white muscle disease. White muscle disease affects young rapidly growing kids, either in the cardiac or skeletal muscles. When affecting the cardiac muscles, kids show signs of respiratory distress and weakness. The condition is generally fatal in less than 24 hours, despite medical treatment. When affecting the skeletal muscles, the kids are weak and stiff, often showing a “saw-horse” stance. These kids respond favorably to supportive care and treatment with vitamin E and selenium. Goats can also suffer from selenium toxicity. This is usually indicated by loss of hair coat, lameness, and diarrhea.
As is seen in this short overview, there is a multitude of factors to consider when choosing a mineral supplement for your animals. Having a good understanding of forages and soils in your area is very helpful. This can be accomplished by talking to your local extension agent or forage suppliers. When creating your herd nutrition plan, it is helpful to consult with a veterinarian or licensed animal nutritionist to ensure the optimum health of your animals. If you are concerned that your herd, or particular animals, are suffering from deficiencies or toxicities of certain minerals, contact your herd veterinarian. Blood concentrations of macrominerals can often be assessed at in-house labs. Trace mineral concentrations can also be assessed by blood sampling, though certain trace minerals are often better assessed via tissue sample, such as liver biopsy. Always, when choosing a mineral supplement, ensure that it is made specifically for goats. Livestock has different mineral requirements. Supplements made for other species, or those for multiple species, will not provide the most optimum supplementation levels. They may even be harmful.
Katie Estill, DVM, is a veterinarian consultant for Goat Journal, Countryside & Small Stock Journal, and Countryside online. She works with goats and other large livestock at Desert Trails Veterinary Services in Winnemucca, Nevada.
Originally published in the November/December 2019 issue of Goat Journal and regularly vetted for accuracy.