The following is an edited transcript of the Ag Future podcast episode , hosted by Tom Martin , featuring Amanda Radke . Listen to the episode on Apple Podcasts or Spotify .
Amanda Radke is a fifth-generation cattle rancher from Mitchell , South Dakota , and a blogger for BEEF Magazine who has dedicated her career to serving as a voice for the nation ’ s beef producers . She travels the country speaking to agricultural groups about hot industry topics .
Amanda joins us to talk about a recent experience as a panelist at an Alltechsponsored conference leading up to the U . N . Food System Summit , where she brought a producer ’ s perspective to an important discussion about the efficient use of resources . Welcome to Ag Future , Amanda .
Well , thanks for having me .
The panel that you participated in looked at the future of protein security and how to maximize the efficiency of production resources without unintended social , cultural and environmental consequences . You were the only producer on that panel . And first of all , I ’ m wondering if you went into the discussion anticipating having to defend production practices .
Yeah . I kind of chuckled because I felt , “ Oh , I ’ m missing the ‘ Ph . D .’ behind my name . I ’ m not sure if I ’ m qualified to speak on this .” And , you know , the Alltech folks assured me , “ No , no , we want someone that ’ s actually , you know , managing the land and taking care of the cattle and can offer that perspective .”
And so , I was really proud to be able to represent beef producers from here and around the world and highlight some of the things that we already do very well in regards to managing our land and responsibly taking
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Quite simply, it works. It helps to decrease the incidents of
scouring that we typically see in the post-weaning period,
helps to maintain daily liveweight gain (and) reduce
susceptibility to disease. It’s relatively inexpensive. It’s
readily available. And of course, we’re seeing increasing
regulation just around normal antibiotic use — so not just
antibiotic growth promoter, which is obviously banned in
the European Union.
And there’s many beneficial effects of zinc oxide — so,
improvements in digestion, immunity. It has antibacterial
actions, (is linked to) improvement in intestinal
morphology and integrity and enhanced antioxidant
capability — all those things that help to get that piglet
through that critical post-weaning period.
And now, there is this EU ban, beginning next
summer, on the use of high levels of zinc oxide in
piglet diets. What’s the problem with zinc oxide in
piglet growth and health?
So, there’s a number of issues. (The) first one will be
toxicity. We don’t actually see that too much, but you can
get toxic effects of zinc in the pig if it’s fed for too long.
Now, typically, they’d feed it for two weeks, which isn’t too
And I should also say, when we’re talking about high
levels of zinc oxide, we’re talking about around 2,000,
2,500, 3,000 ppm, whereas the requirement for zinc to
the pig is 150 ppm. So, we’re not talking about meeting
the nutritional requirements of the piglets for zinc, which
will slightly be elevated levels. So, if you fed them for a
prolonged period of time, you can get toxicity in the pigs,
which we don’t see too much of.
But of course, there’s environmental issues, because
you’re getting zinc secretion into the manure, which is
then applied to the land. There’s also issues with zinc
oxide accelerating antibiotic-resistant genes and the
spread of antibiotic resistance. And there’s an increase
in heavy metal-intolerant genes and the spread of that.
And you also get modification of the microbiotic or the
microbial population. So, there’s a number of concerns
that are genuine around use of zinc oxide.
You just touched on this: There have been recent
reports highlighting the environmental impact of zinc
oxide. Can you expand on that for us?
Yeah. So, I like to say the main issue is related to the
environment, because the pig will just — for itself, it will
just utilize the zinc that’s required for maintenance and
growth, which, I’ve said, is about 150 ppm. So, anything
that it doesn’t use is then excreted into manure. And
obviously, we have to get rid of that manure. So, we
apply it to the land. And due to the nonvolatile or non-
degradable physical, chemical properties of zinc, the
long-term continuous application of manure onto crops
and land progressively increases the concentration of
zinc into the soil, and then you also, obviously, get that
into the groundwater.
There was an interesting study that was published that
looks at zinc levels between the period of 1986 and 2014
from lands that have had the application of slurries and
pig farms where they’ve been using zinc oxide. Now, they
saw a great soil zinc concentration of 2–5%, which doesn’t
seem very much, but when you look at the latter period
between 1998 and 2014, there was an average increase
of over 24%. And obviously, there’s a risk, as I’ve said, of it
getting into the water, affecting aquatic species as well.
Now, we do have risk mitigation measures in place, which
are implemented, such as manure dilution, ensuring that
any manure is spread from a safe distance from surface
waters. But the European Medicines Agency concluded
that these precautions just simply delay the inevitable,
really, which is why we’re seeing the ban next year.
How has zinc oxide turned out to contribute to the
spread of antimicrobial resistance?
So, there’s quite a few studies and reports showing that
zinc oxide does contribute to antimicrobial resistance,
and that’s because the high levels of zinc oxide can
increase the proportion of multi-resistant E. coli in the
intestines of pigs, for example. So, a lot of studies have
shown that you can get an increase in the persistence
and prevalence of methicillin-resistant Staphylococcus,
for example. That’s probably due to the co-localization of
zinc and methicillin in resistant genes.
And you also get a diffusion of resistant genes amongst
E. coli in the intestine of the pig. So, you’re enhancing it
in the pig, which is a reservoir, if you will, to enhance that
resistance even further. So then, you see more resistance
in the feces, in the digesta, and in the colon. And you also
have an issue with heavy metal-tolerant E. coli. I mean,
a lot of those have been identified, which can further
jeopardize the efficacy of zinc oxide. So, there’s quite a
few concerns, now, with this whole resistance issue.
Can pharmaceutical-level doses of zinc oxide in the
early post-weaning period suppress the growth of
Yeah. No, again, this is interesting, because the actual
mode of action of zinc oxide is really poorly understood.
We just know that it works, and it helps get that baby
pig through that post-weaning period, but the impact
on the intestinal microbiota isn’t that clear-cut. So, there
is some data that suggests that in minor or transient
modifications to the hindgut bacterial population,
whereas other studies get a remarkable effect on those
populations — and some do show a suppression of the
growth of the beneficial bacteria, such as Lactobacilli,
showing that you get a reduction.
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