Bighorn Sheep and Disease Issues Cover at PERC Meeting

Bighorn Sheep and Disease Issues Cover at PERC Meeting

Sheep Industry News Contributor

(March 1, 2013) The effort to maintain healthy populations of bighorn sheep on their traditional range has been costly to producers of domestic sheep, owing to the contention by some that domestic sheep transmit deadly ovine pneumonia to bighorns.

Considerable research has gone into ascertaining disease transmission, and so far, says Margaret Highland, DVM, with the U.S. Department of Agriculture’s Animal Health Unit in Pullman, Wash., at least three things can be affirmed:

  • There’s more than one bacteria involved in causing ovine pneumonia.
  • Bighorn sheep can have the bacteria and not get the disease.
  • Scientists have an incomplete understanding of the problem.

“It’s a very complex problem,” says Highland, “and, unfortunately, there is not just one answer how to resolve it.”

Highland is currently embarking on a study that could unravel some of the questions. She noted that most of the experimental studies on disease transmission commingle bighorn and domestic sheep and look at the two species on an equal footing. But in these studies, it’s unknown whether the bighorn sheep were more susceptible to the disease because they had not previously been exposed to bacteria introduced in the experiment.

To help eliminate that variable, Highland has been raising from birth two bighorn lambs that have never been exposed to Mannheimia haemolytica, the bacteria associated with ovine pneumonia. The lambs had no contact with their mother post partum as Highland milked the mother and bottle-fed the lambs.

“This will give us a way to measure that their immune response to the disease is not due to a lack of exposure,” she says. “We’ll be able to get a ground-level knowledge of their immune system in the pulmonary tract.” 

Another study will involve tracking movements of bighorn and domestic sheep known to be in close proximity.

“A big piece of missing information is knowing where bighorn and domestic sheep intermingle,” says Highland. In past studies, bighorns were collared, so their territory was known, and if it happened to be on a sheep allotment, then the domestic sheep were kept off their grazing allotment, a challenge for producers.

But do they ever actually overlap or intermingle? Does a bighorn sheep come near where there is dog or herder activity? 

With a goal to answer that question, Highland says a rangeland proposal has been made to attach GPS tracking collars to sheep in domestic flocks to see if there is actual overlap with bighorns.

Within the next year, she said, this tracking study will be conducted in two locations, one with desert bighorn sheep and the other with Rocky Mountain bighorn sheep.

Research Station
Also in the Production, Education and Research Council (PERC) meeting, Bret Taylor, Ph.D., of the U.S Sheep Experiment Station in Dubois, Idaho, discussed two research station projects, one addressing neonatal scours in sheep and the other on correcting selenium deficiencies.

Taylor says lambs suffer low mortality rates from neonatal scours, but those that have it don’t grow as well. One potential solution is the use of sodium chlorate, which has been shown to reduce problems with E. coli and salmonella in slaughter animals.

“For scours, we’re looking at the effective dose rates, tweaking them to find a level that will work in a production system,” says Taylor.

The current study, involving 40 mature ewes, added chlorate salt to drinking water over five dates at five dose rates, 0, 30, 60, 90 and 120 milligrams per kilogram of bodyweight. So far, it appears that a dose rate of 56-80 mg/kg of bodyweight of sodium chlorate is fairly efficacious without affecting body weight or animal health. 

In 2013, the researchers will work to validate the system in a full-scale production system using potentially thousands of animals.

The study to correct selenium deficiency is a two-year project testing novel, natural products that enhance the long-term selenium status of sheep.

The product being tested is SeCo, manufactured by Intermountain Farmers. With selenium content of 6 ppm, the product is fed for 20-40 days near parturition or early lactation. The ewe consumes SeCo and the lamb gets it through nursing.

Taylor says the treated animals do not need selenium supplement for at least another six months, so it can work while they’re feeding on selenium-deficient range plants. The project is currently being tested on three sheep operations in Oregon.

Range research at the Sheep Experiment Station, says Taylor, includes shrub recovery on recently burned sagebrush communities and grazing practices that can sustain production.

Predator Control
Larry Clark, Ph.D., director of Wildlife Services, told PERC members his agency is currently working on a number of predator control methods, including testing the use of Old World dogs for livestock protection. Three Turkish Kangals to protect sheep from grizzly bears are with flocks now, and six Turkish Kangals for protection against wolves will be added to flocks this year.

As for research on use of  theobromine caffeine to control coyotes, Clark says commercial release depends on showing increased efficacy.

“This looked promising early on,” he says, “but efficacy is the concern.”

Approval requires at least 90-percent efficacy, and research to date has shown only around 70 percent.

Clark noted that where swift fox are found, the use of M-44 ejector device for coyote control has been halted. So Wildlife Services is looking at how to modify the M-44 to reduce impacts on swift fox, including altering the height, pull tension and the mouth piece.

In addition to controlling predators, the agency is looking at how predator control affects natural resources. In Utah, research is assessing the impacts of predator control on mule deer, and, in Wyoming, the impacts of predator control on sage grouse.

An area of new research is focused on control of feral swine, the populations of which are expanding California, New Mexico, Texas and the southeast United States.

“Feral swine carry pathogens and destroy property and habitat,” says Clark, “so we’re looking to see what we can do to curtail the expansion of their range.”

Wildlife Services is developing a toxicant – sodium nitrate – in concert with Australia that Clark said might also serve as a predator control tool.

As with other government agencies, Wildlife Services is concerned about funding.
“Our budget has been flat in real dollars for several years,” says Clark, “But our costs continue to rise. So we’re reaching out to our constituents to see what your priorities are. We’re uncertain about the future as politicians eye budget cuts.”

Mark Boggess, Ph.D., of the USDA Agricultural Research Service, says his agency is also seeking ideas to empower research in light of a potential budget squeeze.

“We’re hoping to recruit members to a sheep industry task force to look at collaborative research projects,” says Boggess, who asked people to contact him with their ideas or their willingness to participate. “We want to build a funding strategy for sheep industry research.”

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