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Exploring the Role of Enzymes in Animal Nutrition

April 21, 2023

Dr. Amy Petry leads a multidisciplinary research lab that works collaboratively with the swine industry to solve critical problems through innovative science.

What insights can we gain about enzymes and their role in animal nutrition? Dr. Amy Petry, assistant professor in the department of animal and food sciences at Texas Tech University, discusses how these enzymes can enhance gut health and fiber fermentability in pigs and improve the energy contribution of fiber in pig diets. Additionally, Dr. Petry shares her experience as a graduate student and provides advice for those interested in pursuing research careers.

The following is an edited transcript of the Ag Future podcast episode with Dr. Amy Petry hosted by Tom Martin. Click below to hear the full audio or listen to the episode on Apple Podcasts, Spotify or Google Podcasts.

Tom:            Welcome to Ag Future, presented by Alltech. Join us from the 2022 Alltech ONE Conference as we explore opportunities within agri-food, business and beyond.


                     I'm Tom Martin for the Alltech Ag Future podcast. Joining us is Dr. Amy Petry, an assistant professor in the department of animal and food sciences at Texas Tech University and an expert in nutritional physiology. Over her career, she has received more than half a million dollars in federal or industry research grants and has published more than 30 referred journal articles, abstracts and book chapters. Dr. Petry leads a multidisciplinary research lab that works collaboratively with the swine industry to conduct basic science that supports, develops or evolves solutions for producers. She's with us today to talk about her work and observations around the use of carbohydrase enzymes in pig diets — particularly xylanase. Welcome, Amy.


Amy:             Thanks, Tom.


Tom:            I mentioned xylanase is a carbohydrase. Tell us about that and how it's beneficial in pig diets.


Amy:             Absolutely. Xylanase is an enzyme that targets dietary fiber. You, me and the pig, we don't produce enzymes that can break down dietary fiber, so we rely on microorganisms to do that. One way that we can help promote fiber degradation, which can be good for improving calorie uptake in the pig — and then, some of the research we've done to improve gut health — is through the use of these carbohydrase enzymes.


                     Xylanase is an enzyme that targets this fiber called arabinoxylan. Arabinoxylan is this really complex non-starch polysaccharide that's found in a lot of cereal grains. Here in the U.S., one of the more predominant sources of this fiber is corn and a lot of the industrial corn co-products that can be commonly seen in U.S. swine diets. Over the past 20 or so years, we've seen an increase in the amount of fiber in a pig's diet due to least-cost (diet) formulation and utilizing more of these industrial corn co-products.


                     What xylanase can do is help break down that dietary fiber. The original goal of supplementing that enzyme was to help improve feed efficiency (and) fiber digestibility and, overall, (to) increase the energetic contribution of fiber. But what has been more fascinating and more consistent of that is this effect — that xylanase likely improves pig viability or reduces finishing pig mortality.


Tom:            You earned your doctorate at Iowa State University. You did that by investigating the properties of xylanase. What were your findings? And how did the information influence your work going forward?


Amy:             Sure. In my Ph.D. work at Iowa State, we really wanted to find out why this enzyme was potentially improving finishing pig mortality, and then (we) tried to “de-dupe” some of the reasons why this enzyme can be ineffective in corn-based products. One of those things comes down to the mechanism of action of this enzyme, what it's actually doing in the pig's gut. We conducted two pretty large experiments that tested five different hypotheses as it relates to how this enzyme might particularly be working in the gut. We did this with seven other collaborators and did a whole slew of data collection. We looked at digestibility across the gastrointestinal tract. We looked at the microbiome, (the) influences of different biomarkers within the serum and within the gut of the pig, as well as taking microscopy pictures of the actual fiber structure.


                     What we found is that this enzyme appears to be doing more than just improving fiber fermentation. When we supplement it, we do get (improved) fiber digestibility. We get a breakdown of this really complex polysaccharide that's in the pig's diet. But in the process of doing that, we really establish more symbiosis with the microbiome.


                     It appears that this enzyme is eliciting two different mechanisms (through) a prebiotic-like effect. In this case, it's selectively upregulating microorganisms that confer health benefits within the pig. We observe this in the small intestine. When we fed pigs this enzyme in the presence of corn-based fiber, we saw an upregulation in three bacterial groups: Lactobacillus, Bifidobacterium and fecal bacterium. The interesting thing about these microorganisms is, in the human sciences, (they) are largely associated with gut health, probiotic candidates and improving gut barrier integrity. The reason for that is they establish this cooperative microbial metabolism where they take these very complex arabinoxylans, the xylanase, (which) we supplement to the pig, (who) breaks it down into these oligosaccharides, and then these microorganisms beneficially digest those oligosaccharides into these things called short-chain fatty acids. Particularly, we see an increase in butyrate production, which is associated with improving gut health. In these studies, we also saw improvements and markers of gut health.


                     This (is the) first indication that there may be a health aspect to feeding a fiber-degrading enzyme that might partially be the causation for why we see a reduction in finishing pig mortality in commercial production. The other half of that is, when we look at the microbiome in the large intestine, where a lot of fiber fermentation actually occurs, xylanase appears to be eliciting what we call a stembiotic mechanism. The concept of stembiotics — particularly in swine nutrition — is pretty new, but it's this concept that an additive can increase fiber digestibility through stimulating the microbiome to further ferment fiber than what the enzyme or the additive is doing itself. We saw that in these pigs, in that, in their cecum, where most of the microbial organisms (reside in) this kind of little vat, that they have actually had more diversity, and they could ferment fiber (at a rate of) three to one compared to that of the control. It was another indication — along with the changes in the microorganisms — that we were indeed improving fiber fermentation. So, those were the two big findings we found.


Tom:            Well, the use of xylanase in pig diets is becoming more prevalent or popular. But does it live up to the promise, to the hype?


Amy:             I think it does for improving finishing pig mortality. We certainly, here in the U.S., know of several field trials — 15-plus — that have shown an improvement in the number of pigs that make it to market. There's still a lot of research to be done in terms of proving feed efficiency. It appears, with this enzyme, when we supplement it with this corn co-product DDGs, that it doesn't really break down the DDGs as much as we had anticipated that it would.


                     I think, for further use of this enzyme, we really need to be able to improve its ability of breaking down DDGs so that we can improve feed efficiency. There's still a bit of a misalignment between those two things. I think, for continual use of this enzyme and improving feed efficiency, we need more research in that area. But certainly, as a tool to potentially improve mortality, it's appearing to live up to the hype.


Tom:            A lot of your enzyme work, as I understand it, has been in growing pigs. How does enzyme supplementation translate to use in cell diets?


Amy:             Yeah. For me, this is a really interesting area, and something that we're trying to do quite a bit of research on. I think that the mechanism that we showed in terms of improving gut health and improving fiber fermentation likely could translate to a cell. There (is) some evidence of that now within the literature. I know of several people, including our own lab, that are doing work in that area. But I think, in terms of improving fiber fermentability and microbiome symbiosis, I certainly think that xylanase could have that role in the cell as well, but it's an area of opportunity for both research and with the utilization of this enzyme in production.


Tom:            I think this began for you as an undergrad at Texas Tech. If you would, tell us about your interest in how diet influences energy.


Amy:             Early on in my research studies, I spent a lot of time reading about dietary energy. My master's work has dealt with, a little bit, in dietary energy. Energy is one of these really complex things that nutritionists have to deal with. It's not a nutrient; it's a part of what nutrients do within the body. We have four different components that provide energy. We have protein, fat, and then we have simple and complex carbohydrates. Particularly in the swine nutrition realm, I think there's a lot of interest in how we can improve dietary energy, because feed costs are high and calories are expensive. It's accounting for — more than 65% of the cost of nutrition in pig production is due to meeting the energy specification of a diet.


                     So, it’s something that I'm really passionate about and keeps me going, and it started early on in my graduate career and then all throughout my Ph.D.: (the question of) how can we improve the energetic contribution of fiber, which is where a lot of the enzyme work comes in. Because fiber is this interesting thing — particularly insoluble fiber from corn — that we don't actually get a lot of calories out (of). In diets that we feed pigs that have DDGs, if you go from 0% DDGs in the diet to about 30%, you increase the amount of fiber in that diet by about 60%. You go from a level (of) between seven and eight (percent) upwards to 15% fiber. Yet the contribution of that fiber to energy is quite small if it's coming from corn — (it accounts for) less than 5% of the total calories that are in the diet. I certainly think there's an opportunity there to improve the amount of energy we can supply the pig if we can understand fiber better and understand fiber fermentation.


Tom:            It's interesting how timing can influence which fork in the road we take in life. I know that you had it on your side after being told that professor John Patience, with whom you'd hoped to do your Ph.D. work, that he was going to be retiring and probably would not be available. But what happened?


Amy:             Yeah. When I was doing my master's work in the area of energy, I was reading a lot of papers around energy. A lot of those came from John and his lab — and particularly his work around energy and feed efficiency. During my master's work, I was looking at a place to go do a Ph.D. I really wanted to study with John because of his interest in energy. At the time, my master's adviser (said), “I don't know if he's taking any more students or if he's got any opening in his programs.” I was pretty early on in my master's (studies), but call it fate. John sent an email to swine nutrition faculty (members) and said, “I am looking for my last Ph.D. student.” I applied and then ended up being John's last Ph.D. student and got to do this really neat stuff with studying xylanase.


Tom:            It's highly unusual to hear of a graduate student who devotes the kind of time and the patience involved in writing a grant to fund their own dissertation research. It's hard work — a full-time job almost.


Amy:             Yes.


Tom:            But you did it. The effort certainly paid off. I think you received about $300,000 (in grants).


Amy:             Yep.


Tom:            I'm just wondering: What advice from that experience can you pass on to others who might be intimidated by that process?


Amy:             The grant writing that happened in my Ph.D. work was in collaboration with John, but John knew that I wanted to do research as, probably, as a future career — and potentially in academia, like I'm doing now. Being involved in the scientific process of putting together hypotheses and an idea and then eliciting funds through it with the industry was a really rewarding experience. I think anybody who's looking to do that kind of work — or in graduate school, in general — you have to have perseverance and a lot of what I like to call grit, the mental fortitude to overcome any kind of obstacles.


                     I think of a lot of times back in my Ph.D. (studies) — you always hit roadblocks when you're doing research. It wouldn't be research if we didn't, and so the persistence of being able to do that (is important). I think, also, being in an environment where you have high collaboration, like we did in that lab, and the ability to learn from others and be supported in those areas was hugely valuable.


Tom:            I did a little bit of reading about your background, Amy. I see that you were a horse girl. Of course, we're here in the horse capital of the world (Lexington, Kentucky), so that leaps off the page to us. But you were a horse girl by upbringing — riding, judging. I just wonder: Could you have imagined then that you would someday become a rising star in the swine world? What attracted you?


Amy:             No, I didn't think that I would. My dad laughs a little bit. When I was graduating college, I said, "I'm going to go (get) a master's in swine nutrition." My dad said, "Of all of my children, I think you're the last person I ever thought would work with pigs." I didn't really know about pigs growing up. I didn't even really know about agriculture a ton. I grew up in an urban background.


                     I was involved in 4-H. That — my connection to horses — was largely through 4-H. But in college, I was able to be exposed to pigs. Working in collaboration with some professors at our pig farm, doing some undergraduate research, was hugely valuable. At the time, I thought I wanted to be a veterinarian, in undergraduate. I really liked chemistry and biology. I was one of those types of students that uncannily liked the hard sciences, but I also liked animals and agriculture. Nutrition really bridged the gap there for me. It combined my interest and learning of chemistry and biology in an application that seemed beneficial to the agriculture sector. Pigs was the model for me to do that, partially through that exposure of undergraduate research, but also because of the swine industry and how committed the swine industry is to making advancements.


Tom:            What sorts of exciting innovations are you seeing in your field, and how will those developments impact your research work?


Amy:             There's a lot of exciting things going on with dietary fiber. You know, our lab, we really focus in on a couple of different areas — looking at the non-nutritive functions of the diet, increasing the energetic contribution of fiber, and then looking at disruptors of the maintenance energy requirements of pigs. In the fiber realm, there's a lot of really interesting data coming out of Europe, where they use a lot more fibrous ingredients, a lot more soluble fiber. (There is some) really interesting work that's looking at the influence of fiber on farrowing efficiency and the rate of stillborns from PEER fields lab. Then there are some others coming out of the University of Queensland.


                     When we think about all these relationships to fiber, I always go back to (one question): What can we do here in the U.S.? There's not all of these things that we — (things that) can be done in other countries maybe are not applicable to the U.S. swine industry. Our group is trying to bridge the gap. How can we utilize fiber? How can we improve our utilization of fiber and really maximize its health potential and attenuate its antinutrient effects? I think enzymes play a role in that. I think there's certainly a place for that — this concept of using designer fibers.


                     So, specific fiber types that we can actually put in very small concentrations within the diet, to me, is really interesting, and (that is) something that's shaping our lab. And then, also, how is the pig actually using the fiber? We've got a really large project coming up that is taking it back to the basics. We're taking it back to, actually, how is the pig utilizing fiber without enzymes? Then we can try to understand what's happening from a host side but also (from) the microbiome that's there fermenting it, from a metabolism perspective, so we can hopefully develop better candidates or evolve current enzyme or other solutions to help improve that contribution of fiber to energy.


Tom:            We've been talking with Dr. Amy Petry, an assistant professor in the department of animal and food sciences at Texas Tech University and an expert in nutritional physiology. Thanks for joining us, Amy.


Amy:             Thank you for having me.


Tom:            For the Alltech Ag Future podcast, I'm Tom Martin. Thank you for joining us. Be sure to subscribe to Ag Future wherever you listen to podcasts.