Pen riders are the first line of defense in most feedlots. An experienced rider might look at several thousand head of calves in a morning's work. Even in the best of situations though, they will tell you how inexact the art and science of pen riding can be in detecting and assessing livestock disease.

So a little up-front help in the feedyard might be appreciated — especially as good pen riders are getting few and far between. That help is available in the form of a health-profiling technology that can assess disease potential in calves before they're delivered from the ranch.

This assessment — oxidative stress testing — has been used for several years in humans. Oxidative stress is the adverse effect cellular oxidants have on physiological function. It's been implicated in the progression of aging and disease afflictions ranging from infertility to schizophrenia.

Oxidative stress is caused by the unchecked activities of free radicals and reactive oxygen species (ROS). These are highly reactive, unstable molecules that, in healthy cells, are created and neutralized as part of normal cell life. It's been shown to be reduced by antioxidants.

However, if the production of free radicals and ROS exceeds the body's natural defense mechanisms, oxidative damage to vital molecules in the body can occur, leading to cell death, explains Bruce Hoffman, DVM, Churchill, MT, director of animal health profiling programs for OXIS International, Inc.

Currently, the Portland, OR-based company is the only firm measuring oxidative stress in cattle blood to help ranchers and feeders identify the early stages of bovine respiratory disease.

“The animal health profiling program assists our clients in recognizing disease,” Hoffman says. “This fall, we'll continue running pre-weaning studies on calves and assess on-ranch risk levels to be used by the feedlots once they arrive.”

The most likely time to take blood samples for oxidative stress testing is at weaning. The animals would then be sorted on arrival at the feedlot based on the test information. Hoffman advises that in order for this profiling system to work, animals must be individually IDed.

“Today, this profiling is more practical for the producer who sells calves into a marketing program or alliance as opposed to a rancher who sells bawling calves through the open market,” Hoffman adds. The volume price for processing the blood samples is about $5 each.

“Tail bleeding is a simple process that just about anyone can do,” he adds. “But, we can provide some training if necessary.”

Oxidative stress profiling might also be valuable in selecting low-risk animals to go into some of the “natural” or no-antibiotic programs. Hoffman says a next logical step for OXIS might be predicting diseases in the dairy industry — mainly mastitis. Beyond that, he says, they may explore relationships between oxidative stress and an animal's genetic programming.

More Accurate Identification

Guy Loneragan is an epidemiologist in the Feedlot Research Group at West Texas A&M University. He's recently published a summary of his six-year study of death loss in 21.8 million placements from 121 U.S. feedlots. His analysis found that respiratory-related deaths are rising significantly.

“We know we've used increasingly better vaccines, antibiotics and other techniques to benefit the health of the herd, but mortality has continued to increase,” he says. “It seems likely that feedlot placements are more susceptible, presumably because they are younger and more immunologically naïve.”

Currently we don't have a way to address high-risk animals beyond blanket administration of antimicrobials to an entire pen of animals.

“The real dilemma is to more accurately identify those animals that need antibiotics and differentiate them from those that don't need the antibiotics,” Loneragan says. “In other words, we really need a better system to both evaluate at-risk animals and treat them accordingly.”

Cattle can be evaluated on a scale ranging from high risk to low risk for likelihood of disease. The rancher or feedlot manager can then manage high-risk cattle to assure early treatment is provided, and likely reduce labor and treatment for lower risk groups in the herd.

Loneragan adds that with increased accountability — to the government, consumers, and within industry alliances — about the overall well being of food animals and the use of antibiotics, health profiling is a valuable resource for veterinary medicine.

Another significant trend affecting the industry is the increasingly short supply of trained feedlot cowboys who are the primary resource for identifying sick animals.

“With the fewer number of trained cowboys and the increasing number of cattle being evaluated per cowboy, the ability of identifying sick cattle is getting more tenuous,” Loneragan explains. “Ultimately, feedlots could allocate a greater proportion of the limited cowboys' hours to those pens that need them the most.”