Page 100 - July_2023

VETERINARY VIEWS
TRACE MINERALS
Not only is it important to balance energy and protein intake, but at certain times of a horses life, such as during growth,
pregnancy, and lactation, it may also be necessary to supplement trace minerals. It is of particular importance to achieve mineral balances of calcium, phosphorus, copper, zinc, molybdenum, and manganese.
Calcium and phosphorus
Calcium and phosphorus should be balanced in relation to each other, at a ratio of 1.2:1 or up to 2:1 calcium: phosphorus. For an adult horse, this ratio may range from 0.8:1 up to 8:1 without untoward effects; however, a growing horse should not exceed a ratio of 3:1. In a growing horse, imbalances may result in developmental orthopedic disease such as epiphysitis, osteochondrosis, and contracted tendons, as a few examples.
Excess calcium is usually present in legume hays and can have adverse effects
on the growing skeleton. Excess phosphorus and/or deficient calcium intake may lead
to “big-head disease” with mobilization of calcium from bone and replacement of bone with fibrous connective tissue; there will be a corresponding increase in size of the skull and jaw, and problems with joints and the potential to develop splints. High intakes
of wheat bran are often to blame for excess phosphorus that interferes with a proper calcium: phosphorus balance.
Many trace minerals work either in tandem or against each other, such as the interactions seen with copper, molybdenum, and zinc. Excess zinc decreases absorption of calcium and copper – developmental orthopedic disease (DOD) may result. Excess molybdenum or excess sulfur creates a copper deficiency as well.
The trick to balancing minerals relies on feed analysis of hay and attention to labels listed on pelleted feed and grains. For horses in key times of growth and development, it is best to consult with your veterinarian about what and how to feed for your individual situation.
Selenium
In certain areas of the United States, soils may be deficient in selenium, which then means the plants (hay and pasture) grown
in those soils are similarly deficient. Known areas of selenium deficiency occur in the
Excess calcium is usually present in legume hays, such as alfalfa, and can have adverse effects on the growing skeleton.
Northwest, along the Eastern seaboard, and around the Great Lakes. Selenium deficiency is particularly hazardous as “white muscle disease” to foals and growing horses, while
in an adult horse it may contribute to muscle stiffness and myositis also referred to as tying- up syndrome. Selenium may be fed as an
oral supplement or injected into the muscle. Vitamin E is commonly used along with selenium supplementation as an antioxidant.
However, caution should be taken to NOT supplement selenium unless indicated by your veterinarian. Soil areas of the country that
are rich in selenium will grow forage that
has at least sufficient quantities of selenium. Certain plants are known as selenium indicators (milk vetch, woody aster, prince’s plume, gumweed, saltbush) and their presence indicates abundant selenium in the soil, and the potential for toxic levels.
Selenium toxicity can be life-threatening if secondary laminitis develops. Initially, the hair coat becomes brittle and dry, and hair is lost from the mane and tail. The hooves develop
horizontal cracks with the potential to lose
all laminar attachments leading to sloughing of the hoof capsule. Selenium toxicity also may result in blindness and incoordination. Hair or blood samples yield information about the selenium status of a horse so dietary modifications may be made.
THE BOTTOM LINE: LESS IS MORE
Before blithely taking a scoop of something out of a bag or bucket and adding to your horse’s feed pan, think about what you are giving, and why. In many cases, “less is more.” Extra feed materials can have multiple effects, not all of them good. They can:
• Put more of a load on a horse’s system to metabolize and excrete
• Lead to imbalances of necessary micro and macro nutrients
• Adversely affect basic health requirements
• Contribute to performance problems, like tying-up or thumps (irregular contractions of the diaphragm)
Selenium deficiency is particularly hazardous as “white muscle disease” to foals and growing horses, while in an adult horse it may contribute to muscle stiffness and myositis also referred to as tying-up syndrome.
98 SPEEDHORSE July 2023
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