Johnson: Livestock producers should be aware

Published 12:00 am Friday, March 25, 2011

By Brad Johnson
For the Salisbury Post
As spring is “springing” all around us, there are several items for livestock producers to be reminded of.
Grass tetany, sometimes called grass staggers, wheat pasture poisoning, lactation tetany and hypomagnesemia, usually occurs when animals, primarily ruminants, are grazing lush pastures in the spring, according to information from New Mexico State University. Grass tetany can also occur in the fall and winter, but much less frequently. Lactating, older cows are the most susceptible. Grass tetany is a worldwide problem with sporadic and unpredictable occurrence for any given area.
Grass tetany is caused by a deficiency of serum magnesium, frequently accompanied by a less-marked decrease in serum calcium. Clinical signs are often not observed and the only evidence is a dead cow. Animals affected by acute grass tetany may suddenly stop grazing, appear discomforted and show unusual alertness, such as staring and keeping their heads and ears in erect positions. Also, they may stagger; have twitching skin, especially on the face, ears, and flanks; and lie down and get up frequently.
Animals get grass tetany most often while grazing cool-season grasses or small grain pastures in spring or fall. Rapidly growing, lush grasses are most dangerous. Grass tetany also occurs when livestock are wintered on low magnesium grass hay or corn stover. It is not usually a problem on legume pastures on in animals wintered on legume hay.
Cattle in the early stages of grass tetany should be handled gently, producing the least stress and exertion possible. Early treatment by, or on the advice of, a veterinarian is very important.
In general, to prevent grass tetany, applying magnesium fertilizer and dolomitic limestone to the soil may increase the magnesium concentration in plants. Local recommendations should be obtained before fertilization. Also, animals can be fed high magnesium mineral, available as a block, mineral salt mixture, or added to a protein supplement. The majority of cattle producers offer high magnesium mineral to their stock.
I’ve seen quite a few cattle around the countryside with bald spots, usually a good indicator of lice and it’s that general time of year.
According to information from the University of Nebraska, the USDA estimates that U.S. livestock producers lose $125 million per year to cattle lice. Heavy lice populations cause lowered milk production, loss of flesh, stunted growth, general unthriftiness and anemia. University of Nebraska studies and studies of others indicate that moderate to heavy lice populations may reduce weight gains of calves by as much as 0.21 pounds per day.
The life cycle of all lice is similar. Lice are host specific and spend all their lives on the animal. Eggs (nits) are deposited on the hairs of cattle. The life cycle from egg to adult is from three to four weeks during cold weather. Reproduction slows dramatically in warm weather.
In the summer, lice generally can be found only in the folds of skin between the legs and body of cattle. In the winter, as populations increase, lice move around the body, often the back, sides, and tailhead.
There are many specific insecticides recommended for lice control. Read, understand, and comply with insecticide labels when treating livestock.
Examine treated livestock after about 14 days regardless of treatment method to determine if a second or continued treatment is necessary.
Most insecticides are not effective against eggs, so lice hatched after treatment may re-infest the animal.
Enjoy the spring weather.
Brad Johnson is an N.C. Cooperative Extension agent in livestock.