Source:  Ann Bagel Storck, MEATINGPLACE.COM, 4/6/10

The answer to reducing or eliminating salmonella and E. coli O157:H7 in beef cattle may lie in environmentally friendly waste products fed to dairy cattle for decades: orange peel and orange pulp.

USDA's Agricultural Research Service and the National Cattlemen's Beef Association have been funding a study examining whether the essential oils in orange peel and pulp may be a feed ingredient for beef cattle that could fight salmonella and E. coli in the animals' digestive tract. The first phase of the research found sheep that ate this ingredient as part of their diet shed less salmonella.

Todd Callaway, a research microbiologist with ARS who's working on the project, told Meatingplace why he expects the study to have far-reaching results.

When and how did the study begin?

This exact study began about a year ago, but the whole project with the orange peel and orange pulp started about four years ago. It's one of those classic stories of sitting with a couple of friends, and …we basically drew a couple of experiments out on the back of cocktail napkins — literally.

The overall project of looking at the orange peel is all the way from the basic feeding of the animal to the effects on the immune system … [to] finding the specific [essential] oil that we could use as a separate feed additive if the orange peel is not viable to be shipped out to cattle. We're trying to understand what's going on, why it works and how we can tweak it to make it better.

Why focus on the potential benefits of adding orange peel and pulp to feed?

I grew up around dairy cattle in Georgia, and especially in south Georgia we feed a fair amount of [orange peel and pulp] because it's a waste product out of the citrus industry. It's been fed to dairy cattle for probably 30 years. It's got good digestibility for cows, … [but] nobody ever thought about it as value-added product.

We were talking about ways to manipulate gut fermentation and get rid of pathogens, and we drifted into essential oils and other phytocompounds. It hit us that essentials oils are in citrus pulp. [One of my colleagues] had information about essential oils stimulating the immune system. All that fit together really nicely. There was this compound that kills bacteria, we feed it to cows anyway, it's got a really high digestibility and it improves their growth, it's doing something to the microbial population and it stimulates their immune system. What would it do to the pathogens?

Why use sheep in the study, and why was the impact on salmonella populations the first element studied? Is it expected that effects on cattle, and in relation to E. coli O157:H7, would be similar or the same?

The reason for [using sheep] is really simple: logistics. We have to destroy the carcasses, and sheep carcasses are a lot smaller. We can burn them faster, which means we can get a few more animals in a study than we could with cattle.

[As far as focusing on salmonella], it was just making sure everything would work — double check how much the sheep would eat in the study. We always start with the easy study, the one with less risk. Any time you work with E. coli O157 there's a risk. Salmonella is less dangerous, so you do your practice work with the safer bug, work out all your kinks.

Cattle and sheep are a pretty good model of each other because of their rumen nature and the way we're feeding them in this study. It's not exactly 100 percent, but it's 95 percent correct.

Once we complete this study, people will have to go to a feedlot and look at the real world. There are other groups and universities that have feedlots on site and can do a study where they're looking at enough animals. O157 is a pain in the butt, because it shows up sporadically in animals, so you need to get large numbers of animals involved in a study. That is something my unit is just not capable of. We do the proof of concept, and then try to get it carried on by someone else.

Talk about the next phase of the study.

We're going to be starting the E. coli experiment the first week of April. It'll be exactly the same study, just using E. coli O157 and making sure it's susceptible to the essential oils in the same way [as salmonella]. It'll take about three weeks to a month to go through that whole study. Probably a week later we'll have the [E. coli] data and get it back to NCBA.

Are you hopeful you'll see the same results with E. coli?

Yes, because in in-vitro studies [the orange waste products] were just as effective against E. coli as salmonella.

Are there other natural byproducts that might be explored in the future that could have similar properties? What are your expectations about the potential long-term impacts of your research?

I think long term we'll see feedlots and dairies start using more of this in the last phase of finishing right before [animals] go into slaughter plants. If we can show the purified oils as a feed additive can work, that might be includable in rations along the way.

I think this will get into the industry within a year or so. I've heard through the grapevine that some places have put in orders for orange peel already based on the preliminary data, so that's kind of exciting.

I believe in this data. It's not a silver bullet; I'm not going to claim it's going to solve the salmonella and E. coli problems, but in our model, it's reducing [those pathogens by] 10 to 15 times the population [prior to the intervention], which is a pretty significant drop, considering how good a job the slaughter plants do at reducing E. coli and salmonella when it comes in on carcasses. We can reduce what's coming in the front door of plant, and they can be even more effective against what goes through.

We're going to look at more phtyochemicals. This is a very green method —it's something that's environmentally friendly. The more of this stuff that we can do that is green, the better off the industry and consumers will be.

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