“We can’t lose this technology ; it’s too valuable. But that doesn’t mean that it doesn’t come at a price or without responsibility,” says Dan Thomson , DVM, Jones Professor of Production Medicine and Epidemiology at Kansas State University.
He’s talking about beta-agonists  and the recent debate about their role, if any, in lame, lethargic and non-ambulatory cattle at the packing plant.
Soon after Tyson’s announcement, Merck Animal Health, maker of Zilmax, voluntarily and temporarily suspended sales  of the feed additive in the U.S. and Canada to address these concerns.
“We remain confident in the safety of the product, based on our own extensive research and that of regulators and academic institutions, and are committed to the well-being of the animals that receive it,” explained KJ Varma at the time. He is Merck Animal Health’s senior vice president of global research and development.
Zilmax is one of two beta-agonists  approved for use in the U.S. The other is Elanco’s Optaflexx® (ractopamine hydrochloride). The products increase feed efficiency and partition more dietary energy to the deposition of muscle rather than fat. They are approved for feeding to cattle during the last phase of the finishing period. Beta-agonists fed to cattle pose no threat to human health.
More than one contributor
“I believe we’ll see issues of slow-moving and non-ambulatory cattle whether or not they’re fed beta-agonists,” Thomson says. “In the cases of cattle I’ve examined with these issues, their blood profile is eerily similar to that of pigs with fatigued-pig syndrome  [FPS].”
A fact sheet from the University of Florida defines FPS as “pigs without obvious injury, trauma or disease that refuse to walk or keep up with contemporaries.” Thomson says pigs with FPS often recover after 4-6 hours of rest. He adds that FPS is different than porcine stress syndrome  (PSS), a genetic recessive disorder that makes pigs more susceptible to stress.
“In some of the cases we’ve examined, very preliminary findings indicate we should also be looking at a genetic predisposition to stress in cattle,” Thomson says. “Bovine stress syndrome [BSS] has been documented in Australia. Based on discussions and descriptions of the clinical signs, matched with serum chemistry from affected animals, I do think we have fatigued-cattle syndrome [FCS]. It could be related to or different from BSS, but both are related to stress.”
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In a fact sheet for pork producers at porkgateway.org, “Management Strategies to Reduce Transport Losses in Market Weight Pigs ,” authors say that transport losses are influenced by many factors. Among these are handling intensity and handling tools, genetics, social hierarchy and pecking order, facility design, management (presorting market-weight pigs prior to loading), and transportation (trailer design, mixing unfamiliar pigs during transport, transport floor space, and transport time/distance). Packing plant conditions (waiting time prior to unloading, unloading procedures and lairage time), and environmental factors (season, temperature and relative humidity) are other considerations.
Similar factors are now being explored in near-finished and fed cattle.
Stressors have grown over time
“Beta-agonists represent a technology that’s been used for a decade in the beef industry, and for longer in the swine industry,” Thomson emphasizes. “I commend Tyson  for taking a needed stand for beef cattle welfare. I also commend Merck for pulling the product off the market until the industry can understand what is causing these issues. Dilemmas are only managed, but problems are solved. These groups are stepping forward to find a solution.”
When FPS was becoming an issue at swine slaughter facilities, Thomson says Elanco changed the label for ractopamine , reducing the maximum dose allowed and placing an FPS warning label on the product.
“Elanco also conducted research that showed animal handling, at the time of loading hogs onto trucks to be transported to slaughter — regardless of ractopamine in the diet — was a key to preventing FPS,” Thomson says. “Its research also showed that reducing transport stress from the swine unit to the slaughter facility can be a contributor to FPS occurrence. Management of these issues, along with a reduction in ractopamine feeding levels, has contributed to reducing the incidence of FPS.”
Thomson emphasizes cattle and cattle management  have changed since the introduction of beta-agonists. Cattle are heavier , for one thing, with more average weight packed on cattle in the name of production and cost efficiencies. Based on genetic trends, cattle entering the feedlot have more potential for postweaning growth, too.
“Directly, beta-agonists increase heart rates and serum creatinine phosphokinase concentrations [a stress indicator] in cattle,” Thomson says. “Indirectly, feeding beta-agonists could cause metabolism issues [digestive upsets and laminitis] through altered feeding times and delivery management of certain rations to certain animals coming on and going off the product. This change in schedule and feed delivery management could contribute to digestive upsets.”
Although Tyson’s concerns were obviously directed at market-weight cattle in its plant, Thomson says evidence from cattle feeders shows certain types of cattle receiving beta-agonists at particular times of the year may demonstrate an increasing risk of morbidity or mortality during the last month of the feeding period.
Management in feedlots  has changed, too. Thomson says sorting cattle into harvest groups is more common today, meaning that every head in a load is bumping against the razor-thin line between just right and too done. For that matter, heavier cattle mean that fewer head make a load. Thomson wonders if the extra room means more jostling and could add stress .
If you add heat stress on a too-hot day, too much distance between the finish pen and feedlot load-out, stressful handling at load-out, a lengthy haul to the packing plant, time spent in packer holding pens during hot weather, too long of a walk on concrete from those pens to the knock box, Thomson believes the combined effect of these and other stressors are creating FCS in some cattle, leading to the ambulatory concerns that prompted the current debate.
Rather than a step backward, though, Thomson views the beta-agonist debate as an opportunity for the beef industry to move farther ahead.
“It will revolutionize the way we manage fed cattle at the end of the finishing period,” Thomson says. “When steroid implants were first introduced in the 1950s, it led to more research into the growth physiology of beef cattle than had ever been done. I think we’ll see a similar result from this discussion. I think you’re going to see a lot of research into cattle physiology and cattle management during the last 30 days before harvest.”
First, though, Thomson stresses, “You don’t know what abnormal is until you know what normal is. As an industry, we haven’t yet discussed or decided upon what normal is when it comes to cattle well-being at each stage of production. We all want to do what is right for the cattle and the beef industry.”
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