Dr. Karen Robertson (Lehe) explains the role of “therapeutic zinc” in pig production, as well as risks associated with its use, including effects on the environment and antibiotic resistance. She also offers insights on other approaches to support piglet health through diet and management.

Q: What role does zinc play in piglet health? 

Dr. Robertson: Zinc, obviously, is a nutrient that pigs need. It’s a part of many enzymes in the body, so it needs to be in pig diets. Zinc can be supplied to pigs in a number of ways, as there are different forms of zinc. However, zinc is also a therapeutic agent. In high levels, 2,500-3,000 parts per million (PPM), zinc oxide, that chemical version of zinc is actually used to mitigate the negative effects of E. coli infections in little pigs.

Zinc oxide is one of the versions of zinc that’s not well absorbed into the pig’s body, so it’s not well absorbed and incorporated into enzymes and things the pig needs for growth and to thrive. But it does interrupt the colonization of E. coli in the gut. So in nurseries where E. coli infections are causing diarrhea, often zinc oxide is added in these therapeutic levels to prevent the diarrhea but also to reduce the amount of antibiotics that are needed to treat that condition at that time.

Q: Are there risks to treating piglets with therapeutic levels of zinc (2,400 PPM)? 

Dr. Robertson: Yes, zinc oxide has a downside when it’s used therapeutically. For one thing, it’s an environmental contaminant, that’s because again, it is poorly absorbed, so it goes straight through the pig. It does its work in the gut for the pig when it comes to E. coli, but then it’s put right out into the feces, which eventually end up on fields and in our environment. Usually on fields that we grow corn, soybeans, and things like that on and so yes, we can have contamination of our environment with zinc.

That’s why some countries are now regulating the use of zinc oxide at these high levels. For example, in 2017 the European Commission said that they’re going to stop allowing zinc oxide at therapeutic levels in little pig diets and have given five years for alternatives to be found so that can be reduced over time. The rule has been made and will be implemented in the next five years, so definitely alternatives to it need to be discovered. The other negative to zinc oxide is that research has shown that its use at these high levels actually contributes to antibiotic resistance. So while on the one hand we’re reducing the use of antibiotics by putting in the zinc oxide instead, we’re also potentially impacting the efficacy of antibiotics, which is a negative. So yes, zinc oxide works great for enteric E. coli, but we need a better solution that doesn’t have the negatives.

Q: More than 20% of US pork is exported. Is zinc a factor in the global pork trade? 

Dr. Robertson: Since zinc oxide is not absorbed by the pig, we’re not talking about a problem with zinc in the meat having too high levels for export markets, similar to antibiotics if you’d have a residue. We’re not really looking at it in the same way in terms of residue, we’re looking at environmental impact. So where that pig is growing is where the environmental impact is going to be the greatest.

Q: Are there alternative strategies to therapeutic zinc that provide similar benefits?

Dr. Robertson: I think the solution to therapeutic zinc is similar to the solution to antibiotic use. That is that if we do everything that we need to do to keep the pig healthy. If we are raising that pig in the conditions we know to be ideal for rearing pigs, if we have strict biosecurity and minimize the introduction of disease, if we utilize vaccines to prevent as much disease as possible, then we’re way ahead in terms of reducing even the need to use these things. Pigs are still going to get sick, we’ll need to be able to still offer them some support.

There are a lot of new technologies being looked at to improve gut health, to understand how the microbiome is set up, to give the pig a strong immune system, and to help it, in cases of disease, support it so that it’s fighting the disease better on its own. By using its own internal mechanisms to take care of pathogens and us offering any kind of support that we can offer for gut integrity of course is going to help with these enteric pathogens. So we’re exploring all kinds of new technologies as an industry to support not just the gut health but also the immune system of the pig. However that’s not enough on its own, we also have to look at environment management. Also, taking out non-nutritive things in the diet that may be damaging to the pig, dealing with things like mycotoxins that create a stress in the diet, all of those things working together to make sure the pig has the best chance to grow and thrive and become wholesome protein for consumption, without being faced with a disease challenge.