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Parasites and the feedlot

For Nebraska feedlot operator Tom Heine, deworming all his incoming cattle makes perfect economic sense. He stops internal parasites dead in their tracks and prevents them from wreaking havoc on performance and health. In addition, he kills costly external parasites like lice, grubs and mites, which improves gains and slaughter weights, makes animals more comfortable and diminishes damage to hides.Heine,

For Nebraska feedlot operator Tom Heine, deworming all his incoming cattle makes perfect economic sense. He stops internal parasites dead in their tracks and prevents them from wreaking havoc on performance and health. In addition, he kills costly external parasites like lice, grubs and mites, which improves gains and slaughter weights, makes animals more comfortable and diminishes damage to hides.

Heine, who owns and operates Heine Farms Feedyard, an 8,000-head capacity lot near Fordyce, is a partner in this diversified farming and feeding operation with his brothers. The family has been in the feeding business for more than 80 years, which has allowed them to accumulate a great deal of knowledge about what works and what doesn't in producing finished cattle.

Parasite control is one practice that works, Heine says, and it's well worth the investment. "We've been deworming incoming cattle for about 15 years," he explains. "It makes sense. Worms cause cattle to gain less, and can make cattle sick. Lice and grubs make cattle less comfortable, causing them to rub more, lose hair and eat less. By deworming, we remove these problems. The cattle feel better. They gain better, and the health is better."

On most of his cattle, last year Heine began using a new kind of deworming product - a long-acting pour-on product that kills a broad spectrum of internal and external parasites. He not only wiped out external parasites, such as lice, mites and grubs, but he gained an extended, 28-day window of control over brown stomach worms, intestinal worms and lungworms.

By using the longer-lasting product, he says he's been able to eliminate most problems associated with external parasites, making his lot virtually clean of this problem.

Even so, many feedlots don't place as much value on parasite control as the Heine operation does. That's especially true when fed-cattle prices are in the tank, which causes feedlots to respond by slashing costs. Problem is, when they cut out parasite control programs, they may be cutting into their bank accounts without knowing it.

Simply put, parasites cost money and diminish profits, but parasite control pays dividends. External parasites alone cost the beef industry more than $1 billion each year. Parasites cost U.S. cattle feeders 26-30 lbs. of finish weight per steer.

The first thing every feedlot operator should realize, adds Heine, is that unless incoming cattle have just been dewormed at the ranch or stocker/backgrounder level, most cattle are infected with internal parasites even if they're coming off wheat pasture.

"Generally speaking, the decision to deworm recently weaned calves is a no brainer," says Mike Hildreth, a parasitologist at South Dakota State University. "It has to be done. If the cattle are a little older, the tendency is for the wormload to go down. But if they're coming off grass, they're probably infected. And it will cost more money to conduct a fecal egg count analysis than it will to just go ahead and treat them."

Second, while infection levels of internal parasites are higher in younger calves, yearling cattle should also be dewormed on entry because they're probably infected, too.

"We deworm everything that comes off grass," explains Kenneth Bracht, who owns and manages Bracht Feeders, West Point, NE. "It's really a necessity."

Third, despite popular belief, high-concentrate or hot rations do not kill internal parasites. While the chances of re-infection are low once cattle have been dewormed and entered the feedlot, if cattle remain untreated, both internal and external parasites will continue to thrive unchecked, causing diminished performance and reductions in health throughout the feeding period.

Fourth, when feedlot operators use long-acting endectocides, they need to use the fully prescribed dosage to ensure their animals are treated properly. If they don't, the product won't work as well as it should, results will be disappointing, and the investment in product, time and energy will be lost.

Two studies conducted by Johnson Research of Parma, ID, show the benefits of deworming yearlings and calves. The first study involved 180 head of crossbred steer calves freshly weaned off irrigated pastures.

These cattle ranged from six to eight months of age when they entered the lot, and all were infected with nematode parasites. The cattle were split into three groups: untreated; dewormed with a traditional dewormer; and dewormed with a long-acting endectocide.

At the conclusion of the test, cattle treated with the long-acting endectocide outgained (0.1 lbs. more per day than the untreated cattle), outweighed (20 lbs. more) and had better feed conversion (0.12 lbs. less per day). They also had the lowest breakeven cost ($61.42/cwt.) and the best cost per hundredweight of gain ($52.65/cwt.).

The second study showed similar, if not better, results. This project involved 180 Hereford yearling steers that were 12-17 months of age. The cattle came from California, but were grazed at the Johnson facility for 90 days prior to entering the feedlot. All of the steers were confirmed to be infected with nematode parasites.

As in the first study, the cattle were split into three groups. Cattle treated with the long-acting endectocide had the highest slaughter weights (54 lbs. more than the untreated cattle), the highest average daily gain (0.3 lbs. more), and the best feed conversion (0.30 lbs. less, dry matter basis). They also had the lowest cost per hundredweight of gain ($53/cwt.) and the lowest breakeven ($63.78/cwt.).

Why the improved performance and higher weights by killing internal parasites like the brown stomach worm? Johnson researchers say parasite control helps the animals' digestive systems function properly. These worms also acutely affect an animal's immune system, diminishing its ability to fight disease and resulting in lower performance, greater death loss and fewer salable pounds.

"I think the major benefit of deworming incoming cattle is the effect it has on the immune system," says Dr. Bob Bohlender, a North Platte, NE, veterinarian. "If you time your deworming program properly, and it works especially well when feedlots encourage ranchers todo so when they vaccinate their calves, you can really get some benefits in the health of your cattle."

Bohlender, past chairman of the National Cattlemen's Beef Association's Beef Quality Assurance Task Force, says it's also important for feedlots to look at external parasites like lice, grubs and mites. These parasites are especially problematic because as they gnaw, suck and scratch their host, they cause cattle to gain and eat less while negatively impacting hide quality.

Damage caused by grubs and mites, for instance, is so extensive and widespread that even the 1995 National Beef Quality Audit listed this problem as one of the most significant economic losses facing the industry. All told, the industry loses $2.36/head on every non-fed animal due to insect damage, and $24 (includes losses due to brands, scratches and insect damage) for every fed animal it produces.

"This is a more serious problem than just a bunch of cattle rubbing and scratching on fence posts," says Bohlender.

Simply put, damaged hides place the industry at an economic disadvantage with other countries. They are "difficult to sell at a profit because numerous defects cause the tanner to use more chemicals, as well as finish, in an attempt to disguise the defects," says Robert Koeppen, Leather Technologies, Inc., of St. Joseph, MO. "The marketplace does not command as good a price for these leathers."

While hide damage caused by grubs can often take place on the ranch long before cattle enter the feedlot, the parasite itself can be easily eliminated upon arrival at the yard. Adult fly populations typically peak during the summer. This is when adult female heel flies, or "gad" flies, deposit their eggs on the legs of cattle. When the eggs hatch, larvae emerge, penetrate the skin, and migrate through the animal's connective tissue for four to five months.

The common cattle grub moves primarily through the tissues near the esophagus, while the northern cattle grub moves in the tissues of fat surrounding the spinal cord.

After developing for two to three months, the larvae migrate again, this time to the subcutaneous region over the back. Here, they live in burrowed-out cavities called warbles, breathing through small air holes cut in the skin.

After developing to the third stage, the larvae emerge through the air holes, drop to the ground and form pupae, which eventually develop into adult flies, starting the cycle over again.

Needless to say, the activity of these parasites can cause production losses. During periods of larval migration, cattle become unthrifty, failing to grow or gain weight at a normal rate. Adult heel fly infestations disrupt feeding and resting patterns and infected cattle occasionally suffer bodily injury.

Another external parasite of great concern to feeders is lice, both the biting and sucking varieties. Sucking lice cost millions in economic loss each year due to hide damage, bruising, reduced weight gains, with indirect losses resulting from damage to equipment and fences due to rubbing. Sucking lice also cause anemia in cattle.

Biting lice, while causing less economic loss than sucking lice, still cause cattle to rub against fences, gates and equipment, causing carcass bruising, in some cases hide damage and less time at the feedbunk.

"For us, controlling lice and grubs is a way to improve efficiency," says Tom Feller, Feller & Company, a feeding operation based near Wisner, NE. "It's really unknown to us just how much of an economic benefit it is to treat our cattle, but we definitely think it does us some good. It eliminates the lice and grubs, and that's good, because when we've got a lice outbreak, the cattle are hard on our fences and gates, and grubs are disastrous in the packing house."

Lice infestations normally peak in the winter months when cattle's hair coats are long and cattle are assembled in pens or corrals, where transmission from one animal to another easily takes place. The hair coats of infected animals are dull and scaly, which also diminishes the value of the hide. Cattle also become unthrifty, eat less and don't gain as well as they should. They become restless, and those that lick excessively can develop hairballs. Because they're not eating or resting properly, infected cattle often become predisposed to secondary diseases, such as pneumonia or anemia.

Research in Wisconsin shows that a single, topical application of a long-acting endectocide effectively controls biting and sucking lice, and minimizes hide, facility and equipment damage. In this 112-day study of 20 crossbred beef calves, researchers compared calves treated with a pour-on endectocide to calves that weren't. They co-mingled these animals in pens with calves carrying severe natural infestations of both biting and sucking lice. To maintain a constant challenge, lice-infested feeder steer calves were rotated every two weeks.

While lice were found on nontreated calves within two weeks of exposure, a single topical application of the long-acting endectocide significantly delayed biting lice infestation in treated calves grouped with lice-infested feeder calves for the length of the 16-week study. The same was true for the long-nosed cattle louse.

"The treated calves did not show significant levels of infestations until 12-14 weeks into the study," says Dr. Larry Smith, Wisconsin veterinarian who conducted the study. "This research shows that this type of product offers protection for cattle against lice over a long period of time, and that it will work well for feedlots treating incoming cattle."

In a perfect world, adds South Dakota State's Hildreth, every animal entering the feedyard would have complete information on its breeding, background and a treatment history for parasites, vaccinations and other medications. Unfortunately, it doesn't work that way, which makes the feeding business more risky.

One way to reduce the risk is to introduce new technology, such as longer-acting endectocides, into feedlot parasite control programs, he says. It's also going to become increasingly important for feedlots to work more closely with the ranchers and backgrounders who provide them with calves and yearlings. By doing so, feedlots and producers can work together to eliminate many of the inefficiencies and product quality problems facing the industry.

"If I was a feedlot operator, the most important information I would need is the history of the cattle coming into my lot," says Hildreth. "If I had this information, I could make more informed decisions about what type of parasite control would be necessary for any given pen of cattle. One of the nicer things about these longer-acting endectocides is that they not only give you effective internal worm control, they also provide producers with flexibility to control the external parasites for a longer period of time. People tend to feel that added benefit is worth the investment."

To Tom Heine, it's more than just parasite control; it's about raising quality cattle in a quality way.

"Our goal is to raise cattle efficiently and make sure we're running a profitable operation" he says. "Since we switched to the longer-acting product, the parasites simply haven't been a problem for us. It's a decision we're glad we made."