Extension Ag Update
September/October 2004
Articles Research Resources Internet Links Ag Facts Education


Farmer Survey Shows Importance of Internet
A survey conducted by the National Farmers Union showed that 86 percent of farmer respondents think future farm success will involve farmers and ranchers and their cooperatives knowing how to effectively manage the Internet for marketing. Fifty-eight percent of the more than 800 responding farmers said they used the Internet for doing farm business for buying and selling. The survey also found that 94 percent of all respondents use a computer, 80 percent use the Internet daily, and 47 percent are interested in marketing the products of their own farm or co-op over the Internet. The survey was conducted both online and at local and state fairs.

Strategies for Rural Revitalization
A new report from the Center for Rural Affairs showcases the efforts rural communities have made to revitalize themselves. Fresh Promises: Highlighting Promising Strategies of the Rural Great Plains and Beyond features economic development strategies employed by a range of communities. These measures include development based on environment, rural microenterprises, agricultural cooperatives for niche markets, and on-farm processing.

Mustard Cover Crops can "biofumigate" the soil for Pest Control
Brassica family plants can be used as a cover crop. As they decompose as green manure, "biofumigation" occurs. Fungi, nematodes and even weed seeds can be killed by this process. Research is continuing in order to understand the processes that cause this effect.

Biodegradable wheat containers could reduce fast food impact

By Marcia Wood, 301-504-1662, MarciaWood@ars.usda.gov, Source- Gregory M. USDA-ARS Bioproduct Chemistry and Engineering Research Unit, (510) 559-5677

Lightweight, biodegradable containers for taking home your fast-food meal or leftovers from your restaurant dinner can be made with wheat starch. Because they're biodegradable, all of these foodservice items offer a more environmentally friendly option than today's petroleum-based, polystyrene foam products. Having a selection of different starches – such as wheat, potato or corn–to choose from gives manufacturers of biodegradable products some purchasing flexibility. That flexibility can help them keep their prices competitive with polystyrene items.

The wheat-based containers can be made in presses or molds that work something like a giant waffle iron. The process begins with pouring the wheat-starch batter onto the heated mold, which is then closed and locked. Moisture in the batter generates steam that, in turn, causes the batter to foam, expand, and fill the mold. The steam is vented and, when the 'baking' is finished, the mold is opened, the product is removed and the cycle starts again. The entire process takes less than a minute. A water-resistant film, added later, helps the container keep its strength and shape.

Using DNA to Detect Pathogens on Plant Seeds

By Sharon Omahen, University of Georgia, 770-229-3219, Source Ron Walcott, rwalcott@uga.edu, 706-542-6963

Using DNA technology, University of Georgia scientists are working to develop a quicker, easier way to detect pathogens on plant seeds. "We started this project in light of our nation's concern over biosecurity in agriculture," said Ron Walcott, a plant pathologist with the UGA College of Agricultural and Environmental Sciences. "Our goal is to develop a system that can detect pathogens in seeds," Walcott said, "whether they were put there intentionally or unintentionally during the seed production process."

The current methods used to screen seeds for fungi, bacteria and viruses can take weeks. The researchers' goal is to develop a quicker, more accurate and precise testing method. "As an example, one of the currently employed tests requires that seeds be planted and grown out to determine if a pathogen is present," Walcott said. "This is time-consuming. And unfortunately, this test is expensive to conduct. And there's a risk of failure, depending on the level of seed infestation." With current methods, he said, it could take weeks to develop a technique to detect a new pathogen suspected to be intentionally introduced into the nation's seed supply. Scientists now use up to five tests to detect different pathogens, he said. A goal of this project is to develop one test that would be used to detect all seed pathogens.

The new detection method will rely on both DNA and RNA to find out whether pathogens are present. "Plants have DNA just like we do, but some viruses have only RNA," Walcott said. "The plan is to use a technique called magnetic capture hybridization to capture and detect the presence of pathogen DNA/RNA in a seed sample." DNA and RNA are the molecules that encode an organism's physiological characteristics. These codes include sequences unique to the organism. By relying on specific DNA or RNA sequences, highly specific and sensitive detection assays can be developed," Walcott said. "As such, this approach is highly applicable for the detection of low levels of pathogens in seeds."

To apply this technique, scientists crush a sample of seeds and mix crude nucleic acids from the seed extract with magnetic, polystyrene beads. The beads are coated with single-stranded DNA, which hybridizes or binds specifically to the pathogen's DNA. The scientists recover the beads with a magnet, then amplify the DNA by polymerase chain reaction. "It's like fishing, but we use mirror-image DNA instead of night crawlers as bait," Walcott said. "This method is highly sensitive and efficient and can work for a wide range of seeds and pathogens. Most important, the turnaround time is just a day." "Once we have the system going, we will have the capability to detect more seedborne pathogens," Walcott said. "If a new one that's not in our database is introduced by terrorists or Mother Nature, it will just take a couple of days to add it to the system."

Organic Farming Is a Winner for Sustainability

By Don Comis, Comis@ars.usda.gov, (301) 504-1625, Source-: Michel Cavigelli, cavigelm@ba.ars.usda.gov, (301) 504-8327 ext. 330, Agricultural Research Center.

An organic crop rotation is at least as sustainable as no-till farming or chisel tillage in terms of nitrogen loss and corn yields, according to an Agricultural Research Service (ARS) study. The five-year study showed that a three-year rotation of organic corn, soybeans, wheat and a legume cover crop had nitrogen losses and corn yields similar to those on land where either chisel-tillage or no-till farming had been used. The organic rotation relied on poultry litter, soybeans and a hairy vetch legume cover crop as nitrogen sources. The study showed the highest risk of leaching nitrogen to groundwater was on fields with no-till or chisel tillage where both commercial fertilizer and poultry litter had been used. Future studies are planned to measure or estimate leaching losses.

Food Safety of 'Organic,' Conventional Beef Not So Different, Ohio State Study Finds

Mauricio Espinoza, espinoza.15@osu.edu, (330) 202-3550, Source: Jeff LeJeune, lejeune.3@osu.edu, (330) 263-3739

Consumers who buy ground beef labeled as "raised without antibiotics" don't always get what they bargained - and likely paid a higher price -- for. A study conducted by Ohio State University food-animal health researcher Jeff LeJeune found similar numbers of food-borne pathogens and antimicrobial-resistant bacteria in samples of ground beef from conventionally reared cattle and from those whose labels claimed to have come from cows that didn't receive any antimicrobial agents.

"At the microbiological level, there was little difference between both sample groups as far as presence of pathogens or resistant organisms," said LeJeune, a scientist with the Food Animal Health Research Program (FAHRP) on the Ohio Agricultural Research and Development Center's (OARDC) Wooster campus. "It's incredible how close these numbers came out."

LeJeune analyzed 150 ground-beef samples (77 conventional, 73 antibiotic-free) bought at retail stores in Ohio, Florida and Washington, D.C. between Jan. 1 and Feb. 28, 2003. While some samples were frozen and others fresh at the time of purchase, all of them were frozen at minus-20 degrees Celsius prior to testing to ensure a uniform analysis -- freezing can damage bacteria and result in a lesser pathogen count.

The beef was cultured and tested for coliforms, E. coli, E. coli O157, Shiga toxin 2-producing E. coli, Salmonella and vancomycin-resistant enterococci. The results: 75.3 percent of conventional beef and 75.3 percent of antibiotic-free beef was contaminated with coliforms; 32.5 percent of conventional and 31.5 percent of antibiotic-free had E. coli; and 8.2 percent of conventional and 3.8 percent of antibiotic-free tested positive for Shiga toxin 2-producing E. coli. Although the numbers vary somewhat, the differences are within the margin of sampling error, LeJeune said.

The level of contamination increased when the meat was cultured in a liquid medium overnight to detect even very low numbers of bacteria that may be present. Still, the difference between beef from conventional and antibiotic-free cattle was still minimal - 87 percent and 89 percent had coliforms, and 77.9 percent and 76.7 percent had E. coli, respectively. No E. coli O157, Salmonella or vancomycin-resistant enterococci were present in any of the 150 samples.

LeJeune said the percentage of contamination and concentration of coliforms found in this study are similar to those reported in the Nationwide Federal Plant Raw Ground Beef Microbiological Survey of 1994. By contrast, E. coli contamination in this study was detected in only half as many samples as reported 10 years ago, and E. coli concentration among positive samples was lower than in the federal survey. "This data suggest that the magnitude and frequency of contamination of ground beef with E. coli has decreased over the past decade, possibly due to the proactive efforts of the processing industry to control microbial hazards," he pointed out. Less E. coli in ground beef is good news. But the presence of antimicrobial-resistant bacteria, especially in the meat from cattle not fed antibiotics, is less encouraging.

Cattle in 83 percent of U.S. commercial feedlots routinely receive antibiotics for disease prevention and growth promotion during the finishing period. This practice, however, has been linked to the development of resistant bacteria, which can be transmitted through food and sicken people with infections that are more difficult or impossible to treat with those same antibiotics.

In the meantime, beef grown without antibiotics is being promoted as less likely to be tainted with antimicrobial-resistant bacteria, and a growing number of consumers are willing to pay higher prices for this assurance. But LeJeune's research shows that at the grocery store, ground beef by any other name can still carry antibiotic-resistant bacteria. LeJeune cultured the same 150 beef samples looking for resistance to 11 antibiotics commonly used in cattle. Again, the difference between conventional and antibiotic-free beef samples was not significant. For example, bacteria resistant to tetracycline -- one of the most commonly used antimicrobial agents in cows -- was found in 18.2 percent of the conventional samples and in 19.2 percent of the antibiotic-free samples. Resistance to the antibiotic ampicillin was detected in 44.2 percent and 32.9 of the samples, respectively.

No data on resistant organisms is available from 1994 to know whether these numbers have increased, decreased or remained constant. "The question is, why are they the same?" LeJeune said. "If the subtherapeutic (growth-promoting) use of antimicrobial agents is the sole driving force for the emergence and persistence of antimicrobial-resistant bacteria in the food supply, one would expect to find fewer antimicrobial-resistant counts in meat derived from cattle raised without the use of antibiotics for growth promotion."

The answer probably lies elsewhere, LeJeune said. Dissemination of antimicrobial-resistant bacteria from farm to farm can occur, possibly though contaminated feed, wildlife and other environmental sources. Cross-contamination can also take place during slaughter and processing. "Meat is sterile in the cow," LeJeune explained. "The majority of coliforms and E. coli that contaminate cuts of beef do not necessarily originate directly from the intestinal tract of the animal from which the carcass is derived. But contamination from other carcasses being processed or processing equipment such as grinders and knives contributes significantly to the spread of bacteria. So if you slaughter and process conventionally reared animals and animals raised without antibiotics in the same place, cross-contamination can easily occur."

LeJeune said that raising cattle without the use of antibiotics will not by itself solve the problem of antimicrobial-resistant bacteria in beef. "From a food safety perspective," he said, "taking away those antibiotics is not going to make a difference unless there is a concerted effort to minimize the spread of resistant bacteria among live animals and reduce bacterial cross-contamination during slaughter and processing."

Food-borne pathogens cause an estimated 76 million cases of illness each year in the United States. Although most bacterial contaminants found in ground beef and other meat products can be destroyed by adequate cooking, 30 percent of Americans eat undercooked hamburger. LeJeune's study was published in the July 2004 issue of the Journal of Food Protection.