Farming Magazine - July, 2014

COLUMNS

Small Livestock: Not Too Little, Not Too Much

By Sally Colby


Lambs with the skeletal form of white muscle disease appear stiff and hunched, and may shiver or tremble due to pain. When detected and treated in time, most lambs with the skeletal form recover.
Photos by Sally Colby.

Nutritional myodegeneration is a big name for a common problem in calves, sheep, goats, chickens and pigs. Also known as white muscle disease (WMD), stiff lamb disease or nutritional muscular dystrophy, nutritional myodegeneration is one of the most common nutritional diseases of livestock throughout the East and Northeast, where the soil is deficient in selenium.

Selenium is a micronutrient, a substance that is required in very small quantities, but is critical to immune function, disease resistance and other bodily processes. Each micronutrient is essential in animal nutrition; too little can cause significant health issues, and too much can be toxic. Some micronutrients have a symbiotic relationship with other minerals or vitamins. Such is the case with selenium and vitamin E.

Penn State Extension veterinarian Dr. Robert Van Saun explained the relationship between selenium and vitamin E.

"Both vitamin E and selenium act cooperatively as antioxidant agents in cells. Vitamin E is located in cellular membranes and prevents oxidizing agents from altering polyunsaturated fats in the lipid membrane. Selenium performs its antioxidant actions as the enzyme glutathione peroxidase, and it reduces oxidized fats and hydrogen peroxides produced during normal cellular metabolism," Van Saun said. "Collectively, these two essential nutrients protect the whole of the cell from damage that could occur from oxidizing agents produced during metabolism, immune responses or from external environmental sources."

WMD can affect skeletal and/or cardiac muscle. Damage to cell membranes leads to muscle degeneration, which can be quite painful for the animal. When skeletal muscle is affected, the animal appears weak and stiff and may have difficulty rising and walking. If the animal is assisted to a standing position, it may shiver, tremble or stand in a hunched position, which indicates pain. When WMD affects cardiac muscle (the heart), the animal may appear to have pneumonia, with labored breathing, fever and foamy nasal discharge.

Animals that are treated as soon as they show signs of the skeletal form of WMD usually respond well. Although some producers use an oral preparation to supplement lambs or kids, a serious case of WMD probably requires an injectable selenium/vitamin E product, which is only available through a veterinarian.

Mature animals that receive adequate selenium and vitamin E should produce young that do not have deficiencies. Some producers boost selenium and vitamin E levels in pregnant animals by administering injectable selenium/vitamin E prior to kidding or lambing.

If young animals in a herd or flock are showing clinical signs of WMD, adult animals should be evaluated for vitamin E and selenium status. "I prefer to provide nutrients through the diet in a traditional manner, but in clinical disease situations, then parenteral [injected] doses may be necessary to head off serious problems," noted Van Saun.

Animals that are deficient in selenium and vitamin E will be unthrifty and often have reproductive issues, including low conception rate, fetal loss and low milk production. Selenium toxicity can be the result of errors in feed formulations, ingestion of plants that accumulate selenium (not common in the East/Northeast), and overadministration of injectable selenium/vitamin E supplement.

Van Saun said that standards established by the National Research Council (NRC) determine suggested nutrient requirements for a given species. "The recent NRC publication for small ruminants [sheep, goats, cervids, camelids] would suggest the requirement for selenium is 0.3 parts per million of the total diet," he said. "The daily requirement would be approximately 0.7 milligrams selenium per day. As for vitamin E, the requirement will depend upon physiologic state [maintenance, pregnancy, lactating, growing]. Growing kids and lambs have the highest vitamin E requirement."

On some farms, only a portion of newborn animals will show signs of WMD while others appear to be fine, despite all the females receiving the same ration and supplemental minerals. Van Saun said this is due to the fact that not all animals consume exactly the same amount of feed that is offered in a group setting, along with the potential for variation in intake levels of free-choice mineral supplement.

"Selenium is very efficiently transferred from dam to fetus, whereas vitamin E is not," added Van Saun. "Vitamin E can be concentrated in colostrum, which is the first big supplement to the newborn animal. The amount of selenium or vitamin E transfer across the placenta or into colostrum will depend on the dam's nutritional status for that nutrient. With variation in intake across individuals in a herd or flock, there will be more variation among the newborn animals relative to their nutrient status. The more potential variation of nutrient intake among animals due to feed availability, competition within the flock or herd, sorting and selective feeding, [the] more variation among newborns."

Commercial poultry rations are formulated with the correct levels of nutrients, and chickens that have access to good green grass should receive adequate vitamin E. However, they may still be deficient in selenium if they are being raised on pasture. Commercial swine rations also contain nutrient levels to meet the animal's requirements, but pigs being raised on pasture may require supplementation.

If you suspect that your animals might be suffering from a lack of selenium/vitamin E, work closely with your veterinarian to determine how to provide the correct level of supplementation.

The author is a frequent contributor and freelance writer who farms and raises Great Pyrenees in south-central Pennsylvania. Comment or question? Visit http://www.farmingforumsite.com and join in the discussions.