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Preserving Availability Of Antibiotics

The University of Minnesota is working with the National Pork Board to develop a decision-making model to preserve antibiotic use in the prevention and control of swine diseases.

The University of Minnesota is working with the National Pork Board to develop a decision-making model to preserve antibiotic use in the prevention and control of swine diseases.

The European Union's move to ban the routine use of antibiotics in animals, and the Food and Drug Administration's proposal to curtail their use in the U.S., has helped launch a modeling project to defend their use.

“Many critics argue that the current restrictions of use in food animals (and in humans) are inadequate and that excessive use is leading to unacceptable risks to humans,” says John Deen, DVM, director of the University of Minnesota Swine Center.

To effectively respond to these charges, he and fellow researcher Robert Morrison, DVM, are designing a decision framework that sets out objectives to create new descriptions for antibiotic use and refines drug use on farms.

Model Objectives

The model will take into account three objectives:

  • Reducing the potential effects on the welfare of pigs by swine diseases. “We are used to describing problems in economic terms such as morbidity and mortality (Figure 1). But we have to describe it (the use of antibiotics) in welfare terms as well,” explains Deen. “The number of days that a pig is sick is often a conditional measure of pig welfare. We also have to point out that the use of antibiotics does improve the welfare of the pig.”

    He continues: “We've got to answer the antibiotic critics and point out that there is a care component to all of this.

    “Frankly, that is an emphasis that has been lost and that vernacular needs to be put back into veterinary medicine,” stresses Deen, chair of the American Association of Swine Veterinarians animal welfare committee.

  • Measuring the financial impact of swine disease and the costs of intervention, including antibiotic use.

  • Accounting for the amount of antibiotics consumed to address some concerns of an indirect relationship between antibiotic use and the development of resistance.

Deen says the goal of this model is not to formulate a “final answer” for proper animal antibiotic use. Rather, it will model the benefits and costs to different groups.

The model can't define the proper balance between consumer safety, pig well-being and economic benefit. Each group should be involved in a dialogue that expresses their needs, he notes.

Drug Treatment Dilemma

A major obstacle inherent in the pork industry is that the costs and benefits of pig production and antibiotic use are seldom limited to a single animal.

Pork producers work with groups of animals at a time. “In other words, treating a pig in the nursery has an effect upon that pig, but also affects the likelihood of disease transmission and thus, the overall extent of the disease,” observes Deen.

Many critics don't understand that concept. They think antibiotic use should be limited to treatment, just treating the pigs that are observed as being sick. The problem with that approach is seldom are all of the animals in a population sick at the same time, he says.

The use of antibiotics for prevention and control of disease is a common but poorly documented practice.

“Much of what has been attributed to growth promotion is actually prevention and control of disease,” Deen emphasizes.

Modeling Challenge

Modeling disease treatment is fairly simple, he says, because you can pick out the sick pigs, determine the antibiotic treatment needed and assess the outcome of that treatment.

The use of antibiotics in prevention and control, however, doesn't offer those types of ready answers.

But a preventive antibiotic program can work well for diseases such as Streptococcus suis. “When you see a case, you've got to move beyond treating affected pigs, because diseases like Strep. suis hit the pig so hard that demanding a treatment protocol is really naïve; you simply can't catch them that fast,” says Deen. Figure 2 models the results of different treatment protocols for an outbreak of Strep. suis in the nursery.

In short, a main goal of the model being developed will be to show that therapeutic treatment restrictions — only treating visibly sick pigs — takes away the ability to prevent and control problems.

With some diseases, untreated penmates may turn up sick a week later, and that's providing poor animal welfare, says Deen.

Deen's talk was given at Pork Academy prior to World Pork Expo in Des Moines, IA.