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Cutting Wormer Dependence


By Alan Harman


The need to rid lambs of worms can be minimized by rotational grazing and by checking animals’ inner eyelid color for signs of anemia, a U.S. Agricultural Research Service (ARS) study confirms.

The finding comes as a result of work by scientists, veterinarians, and extension agents from the Southern Consortium for Small Ruminant Parasite Control, formed in response to the threats posed by worms resistant to parasiticides.

Animal scientist Joan Burke examines FAMACHA scores of lambs. (USDA-ARS photo by Peggy Greb)
Animal scientist Joan Burke examines FAMACHA scores of lambs. (USDA-ARS photo by Peggy Greb)

Unnecessary worming (increasingly referred to as deworming) speeds the development of resistant worms.

“Using alternatives to conventional parasiticides fits well into organic and grass-fed management systems and meets consumer preferences of minimizing chemical residues in the meat,” ARS animal scientist Joan Burke says.

The blood-sucking worm, Haemonchus contortus, can cause severe anemia in animals. It is called the barber pole worm for the females’ spiraling white, egg-filled ovaries around blood-filled intestines.

Worldwide, they cost farmers and ranchers millions of dollars in losses. Animals shed worm eggs with their manure, and the larvae that hatch can be eaten by other livestock.

Burke found that gel capsules filled with copper oxide wire particles eliminated the need for conventional wormers in all but one case. And lambs that also rotated pastures needed fewer wormings with the copper oxide pills.

The researchers used a tool called FAMACHA to determine whether to worm their study animals. They compared the lambs’ eyelid color with FAMACHA photos of the eyelids of sheep at five levels of anemia. The stages range from the red eyelids of healthy livestock (Stage 1) to almost white eyelids of severely anemic livestock (Stage 5).

FAMACHA is named after its developer, South African livestock parasitologist François “Fafa” Malan, and is used by farmers or ranchers to determine when to worm their animals—and to avoid unnecessary wormings.

The researchers tested 71 lambs naturally infected with the barber pole worm in the first-ever study of rotational grazing that started with worm-infested lambs.

The researchers used an alternative wormer, a gel capsule filled with copper oxide wire particles. They wormed only animals whose inner eyelid color was medium pale—Stage 3—on the eye-color chart.

Comparison of the lamb's eyelid color with the FAMACHA card containing photos of sheep eyelids at five levels of anemia. (USDA-ARS photo by Peggy Greb).
Comparison of the lamb’s eyelid color with the FAMACHA card containing photos of sheep eyelids at five levels of anemia. (USDA-ARS photo by Peggy Greb).

Only one lamb did not respond to the copper oxide and required conventional treatment. Nineteen lambs did not need any worming.

Some of the lambs grazed on Bermuda grass in the same pasture all season, and some were rotated every 3.5 to 7 days. They returned to the initial pasture 28 to 35 days later—three times over the 105-day grazing season. The lambs that rotated pastures needed fewer wormings.

“This is the first study of rotational grazing that used lambs that had worms,” Burke says. “This is the only way you can find out whether rotational grazing has any advantages over continuous grazing for organically-managed animals.”

Rotational grazing may prevent animals from concentrating worm larvae because they are not bedding down in the same area every night. Also, neither pasture was overgrazed, an important consideration in both minimizing reinfection of livestock and maintaining healthier pastures.

[Editor's note: Some readers who have enrolled in the FAMACHA program in order to obtain the tightly-controlled evaluation cards have discovered the card's colors tend to fade over time, particularly with repeated use on bright days. Please see the article Organic Worm Control—sheep! Nov/Dec 2008, p. 42—which explains use of paint-store sample chips in fabricating a homemade assessment card. Also in that article: Explanations of one grower's rotations and garlic worming schedules, plus culling to raise overall worm resistance.]





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