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Zinc’s negative effects on mineral digestibility can be mitigated, study shows

Published June 1, 2017

URBANA, Ill. – Researchers at the University of Illinois have shown that a common strategy for reducing postweaning diarrhea in pigs may have negative effects on calcium and phosphorus digestibility, and are suggesting management practices to counteract the effects.

The biological requirement for zinc in growing pigs is approximately 50 mg/kg body weight. However, pharmacological levels of zinc—2,000 to 3,000 mg/kg—are sometimes included in diets fed to pigs after weaning. The high levels of zinc help to prevent postweaning diarrhea, but are not without drawbacks.

"Zinc competes with calcium for absorption in the small intestine of the pig," says Hans H. Stein, professor in the Department of Animal Sciences at U of I. "In addition, zinc can form complexes with phytate molecules, which prevents them from being hydrolyzed by phytase to release phosphorus. Therefore, if zinc is included at pharmacological levels in the diets, it can reduce calcium and phosphorus digestibility."

Stein led a team of researchers to determine if pharmacological levels of zinc oxide in pig diets affect the ability of microbial phytase to improve calcium and phosphorus digestibility. They fed growing barrows diets containing either 0 or 2,400 mg/kg zinc in the form of zinc oxide, along with either 0, 1,000 or 3,000 units of phytase (FTU) per kilogram.

Standardized total tract digestibility (STTD) of calcium was 70.0 percent for pigs fed diets containing no zinc oxide and no phytase. Apparent total tract digestibility (ATTD) of phosphorus in the same diets was 61.5 percent. However, when zinc oxide was included in the diets, those values dropped to 67.2 percent for STTD of calcium and 55.6 percent for ATTD of phosphorus.

Adding microbial phytase improved calcium and phosphorus digestibility in all diets. However, the improvement in digestibility was reduced in diets containing zinc oxide. In the diets without zinc oxide, adding 3,000 FTU of phytase increased the STTD of calcium by 16 percent, but the increase was only 9.7 percent in the high zinc diets. Adding 3,000 FTU of phytase increased the ATTD of phosphorus by 31 percent and 21 percent, respectively, in diets without and with zinc oxide.

Stein offered guidelines for producers based on the new research.

"If pigs need pharmacological levels of zinc, the calcium and phosphorus in the diets may need to be increased by 4 and 9.5 percent, respectively, for 15 kg pigs. Alternatively, diets can be supplemented with microbial phytase to prevent reduced absorption of calcium and phosphorus, but the efficacy of phytase will be reduced."

The paper, "Effects of zinc oxide and microbial phytase on digestibility of calcium and phosphorus in maize-based diets fed to growing pigs," is published in the Journal of Animal Science. It was co-authored by Laia Blavi of the University of Illinois, and David Sola-Oriol and José Francisco Perez of the Universitat Autònoma de Barcelona.

News Source:

Hans Stein, 217-333-0013

News Writer:

Jennifer Roth, 217-202-5105

More to it than just the milkweed

Published June 1, 2017

URBANA, Ill.–Most Illinois gardeners believe that monarch butterfly populations are declining due to the lack of milkweed in the summer breeding areas of our state. However, researchers Greg Spyreas and David Zaya with the Illinois Natural History Survey are proving there may be more to the monarch story than milkweed.

Illinois is home to 19 native milkweeds. In the last 20 years, milkweed has decreased by 95 percent in agricultural fields, Zaya says. “However, natural areas are buffering that loss, enabling the monarchs to build up their normal population numbers throughout the summer.”

Plant ecologists like Spyreas and Zaya now believe the decline in the monarch population may also be due to a lack of floral resources during the butterflies’ journey back to Mexico. To provide resources to monarchs on their long voyage, scientists are urging gardeners to create a monarch corridor, also known as a floral highway.

Creating floral highways requires planting fall-blooming perennials in gardens in addition to milkweed. “Keep planting milkweed, of course. It’s a larval food source for caterpillars and a highly sought-after nectar resource for adult monarchs,” Zaya says.

If you plan to add new plants to your garden or to begin building a new landscape, Spyreas has several plant recommendations. “Fall-blooming perennials like liatris, joe pye weed,blackeyed Susan, bee balm, aster, coneflower,and helianthus would be excellent additions to your gardens for the late feeding of monarch butterflies,”he says.

Liatris pycnostachya (prairie blazingstar) blooms in mid to late summer on large upright spikes in pink or purple. This plant requires full sun, and is not drought tolerant when young.

Eutrochium purpureum (joe pye weed) blooms in mid-summer to early fall with a pink or purplish-pink panicle of compound flowers. It requires light shade to partial sun.

Rudbeckia hirta (blackeyed Susan) blooms in early to mid-summer with a dark brown central cone and yellow petal-like rays. It requires full sun and is an easy-to-grow but short-lived biennial.

Monarda spp. (bee balm) blooms in summer for up to two months with a 3 to 4 inch ring of tubular flowers ranging from pink to red. This plant requires partial sun and moist conditions.

Symphyotrichum shortii (smooth blue aster) blooms in late summer to fall with flowers featuring blue-violet petal-like rays and a yellow center which last one to two months. It requires partial to full sun and regular pinching to keep compact.

Echinacea purpurea (purple coneflower) blooms mid to late summer with a central brown cone with purple or pink petal-like ray flowers. The plant requires full to partial sun and prefers well-drained soil and is drought tolerant once established.

Helianthus mollis (downy sunflower) blooms in late summer to early fall with a large bright yellow composite flower. It requires full sun, tolerates drought, and forms dense colonies.

Additional gardening practices like adding a water source, planting multiples of one plant type in groups, avoiding pesticide use, allowing herbs to flower,and planting annuals like Mexican sunflower, zinnias,and cosmos can be of great benefit to the traveling monarchs.

University of Illinois Extension horticulture educator Kelly Allsupsays,“By creating a floral highway to help the monarchs, you will also help a host of other pollinators and wildlife by creating habitat they need to survive.”

News Writer:

University of Illinois Extension

At $8 per piece, is buying a Buddha-shaped pear foolish or fun? Your age may predict your answer.

Published May 31, 2017
pear shaped like a Buddha
Photo courtesty of Fruit Mould

URBANA, Ill. – Square watermelons, star- and heart-shaped cucumbers, and even Buddha-shaped pears can be found in some grocery store produce bins. Who buys them? And why? A recent University of Illinois study found younger consumers with an eye for adventure are more likely to purchase these avant-garde fruits.

First of all, growing a pear shaped like a Buddha is not an easy task. There is a lot of physical labor involved. A clear plastic mold must be placed over each new pear fruit as it begins to grow, then removed when the fruit is large enough to fill the mold. The harvest time is critical for shipping. It’s no wonder they retail for $8 to $9 per piece.

“Before we started researching this, we had no idea that there were so many different novelty-shaped fruits and vegetables on the market,” says U of I agricultural communications professor Lulu Rodriguez who led the study. “We were curious. How do growers find buyers for such  unique food products?”

Rodriguez says she and her team started with the theory of reasoned action to help explain why people might purchase something like this. The theory is based on the assumption that human beings usually behave in a sensible manner. Their intention to perform an action, the theory says, is influenced by their attitude toward the behavior and their subjective norms, particularly whether they sense that those who are important to them agree with and support that action.

“At first glance, buying a Buddha-shaped pear seems like an irrational purchase. So we thought, there must be a hedonic, consumer motivation for wanting to own such an unusual item—that is, just for the sheer pleasure of owning it. The undergrads we talked to said at $8 a piece, they’d buy one Buddha pear, take a picture of themselves holding it, and post it on Facebook. It was something to brag about,” she says. “They’re obviously not purchasing the pear for its nutrition. So we included a novelty-seeking component by adding a few questions to the survey and then correlating the answers to see a path of influence.”

For the study, 336 people participated. Respondents first read a news article about the novel pears, then completed a questionnaire that included questions about their attitudes toward the pears, what they think their friends and family think about the idea of buying these products, their novelty-seeking tendencies, whether or not they would buy them, and how much they’d pay for them. The survey also collected demographic information—including gender, age, nationality, education level, religious affiliation, and household income.

The results show that younger consumers with lower incomes are more inclined to purchase the uniquely shaped pears, not older consumers who may have more disposable income to splurge on them.

“That was surprising,” Rodriguez says. “I thought people with higher incomes and more to spare would be more likely to buy a box of the pears to impress a friend or business associate. But we think younger people see them as something adventurous. Older people may just think the pears are foolish.

“Our findings do suggest that marketers can target people who like adventure and seek new experiences by making every effort to reduce boredom, and avant-garde fruit shapes are likely to fill the bill,” Rodriguez says. “Those who sell the regular fruits might try making simple changes that can create a new mood to entice the novelty seekers.”

Rodriguez says the novelty-shaped pears are grown in China in an orchard that is no different than any other, and it’s likely only a small portion of the trees are relegated to growing the novelty-shaped fruit. The unconventional shapes mean big profit for the growers—about 1,000 percent greater return for their investment and labor.

“I doubt that American farmers would try this as a value-added product. It’s just so funky,” Rodriquez says. “It caters to a very niche market. Putting molds on the fruit, monitoring the growth, and harvesting them takes a lot of labor. In China, labor is abundant. It’s easier there for a grower to do that.”

The article, “Testing an extended reasoned action framework to predict intention to purchase fruits with novel shapes,” is published in the Journal of Agricultural and Food Information. The research was conducted by Lulu Rodriguez, Supathida Kulpavaropas, and Sela Sar.

Rodriguez is also the director of the agricultural communications program in the College of Agricultural, Consumer and Environmental Sciences in the Department of Natural Resources and Environmental Sciences and the College of Media.




Too much of a good thing: Developing safe level guidelines for bioactives

Published May 30, 2017

URBANA, Ill. – The good news is out that wine and dark chocolate may be good for your health. That’s because of substances known as bioactives that are contained in those foods.

Research has shown the potential health benefits of bioactive nutrients—those compounds found in foods like fruits, vegetables, tea, and cocoa. And consumers are showing an increased interest in learning more.

But can there be too much of a good thing?

John Erdman, a professor emeritus in the Department of Food Science and Human Nutrition at the University of Illinois, and his lab have studied bioactives and their health benefits for years. Now, Erdman and a team of other scientists want to see recommended maximum intake levels established by public health officials in order to help educate people about what they should be consuming. Such guidelines are needed whether bioactive nutrients are consumed from fruits or vegetables as part of a healthy diet, or from supplements derived from those foods.

In a series of recently published papers, including a study in the journal Regulatory Toxicology and Pharmacology, Erdman and colleagues report that the key to establishing appropriate levels is assessing bioactives’ safety and potential toxicity: In other words, how much is too much before there are adverse side effects?

“There’s been a huge amount of interest in bioactives in foods, not only in the College of ACES at Illinois, but around the world, as they relate to cancer, heart disease, diabetes, and longevity. Often times we’ll use an animal model or cell culture model to test a bioactive to see if it has efficacy. I don’t think very many people think about the safety side, though,” he adds, pointing out that even life-essential things like water or oxygen, can be toxic if too much is taken in.

Tolerable upper intake levels (ULs) for essential nutrients in the United States were set after a review period between 1994 and 2004. But bioactives, as supplements, remain unregulated. Unlike vitamins, such as vitamin C, or essential nutrients like iron or zinc, bioactives are non-essential compounds in food. But they could influence health if consumed by the appropriate population in the right amounts, Erdman says.

So, if bioactives promote health, and scientists can demonstrate that, then what criteria must be met to have recommendations like Recommended Dietary Allowances (RDAs) or Dietary Reference Intakes (DRIs) set for bioactives?

The answer is two-pronged, Erdman says. It’s about determining efficacy (how well it works and how much is needed) and safety (at what level might the compound produce adverse effects), a risk-benefit curve.

“If we’re going to make recommendations for something like resveratrol, a compound in red wine, as an example, or lycopene, the red pigment in tomatoes, we should have an idea about how much is really needed for efficacy. How often do you need to consume it? And are supplements of resveratrol or lycopene absorbed by humans and stable in the bottles? If you just go to a health foods store for supplements, you don’t really know what you’re getting,” he says.   

Erdman and his lab have been interested in bioactives in foods like soy, tomato, and broccoli for some time, particularly for reducing the risk of cancer. They have focused in on carotenoids, which are found in the pigments in foods such as tomato and carrots. Most recently, though, Erdman has focused his research on lutein. Lutein is also a carotenoid primarily found in green leafy vegetables, but also as the pigment of egg yolks and corn.

“There’s been a lot of research showing that lutein is very important in eye health, Erdman says.

Demonstrating the health benefits in these substances and determining the safety of the substances when consumed can be difficult because a lot of data from human clinical trials are required.

“To establish ULs, ideally we would rely on cases where chronic intake of a compound caused an adverse effect. But usually we don’t have that kind of data,” Erdman says. “For vitamin A, for example, there is an UL mostly that’s based on cases where someone took a larger amount of vitamin A and then had some liver problems. Or magnesium where the upper level is based on severe diarrhea, which is not life threatening, but an adverse effect. We can use the same approach for bioactives, but what it requires is human trials. There are many challenges, because they are expensive to run and who is going to pay for them?”

The paper includes case studies in which two bioactive nutrients as supplements were reviewed for risk and benefit; lutein and ECGC, a green tea extract. For lutein, studies showed efficacy and that the only adverse event that’s been shown is non-life threatening yellowing of skin. As far as the ECGC study, Erdman says it serves as a very good warning. “We’ve known for a long time that drinking tea is very helpful and has good benefits in regards to cardiovascular health and, some studies show, blood pressure reduction. But if you pull out one compound from tea and consume it as a dietary supplement at very high levels it can be toxic, and this was shown for the liver in some persons consuming supplements high in ECGC.”

Erdman adds, “You don’t want people thinking they are improving their health by consuming large amounts of the material and are actually causing harm. In order to make recommendations you have to know what the upper safe limit of the material is. In many cases that’s not known very well. There has been much less work done with bioactives.”

Until dietary recommendations are set for bioactives, Erdman says that he and the group of scientists he works with will continue carrying out research and presenting their information at meetings and symposiums. “We all would like to see some guidelines put in place, and recognition that there are some very important bioactives in foods. Let’s recognize them and under what conditions they should be used, and then let the public know. Most of them come from plant foods—fruits or vegetables—and some come from grains. As nutritionists, we want people to eat more fruits and vegetables and whole grains. Hopefully we can give them another reason, and that is because there are bioactives in these foods, not just vitamins. For people who ignore fruits and vegetables and take a vitamin pill, they are not getting these bioactives.” 

“Bioactive nutrients—Time for tolerable upper intake levels to address safety,” is published in Regulatory Toxicology and Pharmacology. Co-authors are Allison A. Yates, John W. Erdman, Andrew Shao, Laurie C. Dolan, and James C. Griffiths.

Chronology of a sideways corn market

Published May 30, 2017

URBANA, Ill. – Expectations for the magnitude of supply, consumption, and ending stocks for the 2017-18 U.S. corn marketing year have remained remarkably stable for the past several months. According to University of Illinois agricultural economist Darrel Good, as a result, futures prices for the 2017-18 marketing year have remained in a narrow range.

“At the Outlook Forum in late February, the USDA projected that the 2017 crop would be more than a billion bushels smaller than the 2016 cropresulting from a reduction in acreage and a return to trend yield,” Good says. “Consumption during the upcoming marketing year was projected to be smaller than during the current year, mainly as a result of smaller exports stemming from the much larger 2017 South American crop.  Year-ending stocks were projected to decline only marginally from the level of ending stocks projected for the current year. December 2017 corn futures were trading near $3.90 at the time those projections. The price of that contract varied between $3.80 and $4.04 leading up to the USDA’s release of the Prospective Plantings report on March 31.”

The Prospective Plantings report confirmed producer intentions to reduce corn acreage by about 4 million acres in 2017. The price of December futures varied between $3.80 and $3.96 following the release of that report and leading up to the USDA’s release of the World Agricultural Supply and Demand Estimates report on May 10. That report contained the first USDA projections of supply and consumption for the 2017-18 marketing year since the Outlook Forum in February. The projections in the WASDE report were very similar to those made in February. The supply forecast was slightly smaller, reflecting prospects for slightly smaller stocks of old-crop corn at the beginning of the marketing year. The projection of feed and residual use and exports were each 25 million bushels smaller than the February projections, but the projection of domestic food and industrial uses was 130 million bushels larger than the February projection.  Stocks at the end of the 2017-18 marketing year were projected at 2.11 billion bushels, 105 million bushels smaller than the February projection and 185 million bushels smaller than the projection of stocks at the end of the current marketing year. Since the release of that report, Good says the price of December futures has varied between $3.82 and $3.95.

“The very narrow range for corn prices over the past three weeks occurred even with   areas of excessive rainfall that delayed planting and has required or will require some replanting,” Good says. “In spite of the delays, planting and emergence progress as of May 21 was very near the average of the past five years and the percentage of the crop planted after May 20 was very near the average since 1986. Initial crop ratings in some of the wetter areas, however, were much lower than normal. With December corn futures now near the low end of the range experienced over the past eight months, the market is clearly not reflecting much concern about the spotty start to the 2017 growing season.”

According to Good, there are likely a number of reasons that the corn market still expects U.S. corn production to be near the 14.1 billion bushels suggested by planting intentions and trend yield.

  • First, planting delays may not have been extensive enough to result in reduced corn acreage due to abandonment, prevented planting, or a switch to soybeans.
  • Second, it is generally recognized that corn yields are mostly influenced by summer weather, not spring weather, and that dry weather represents more threat to yields than wet weather.
  • Third, the recent pattern of U.S. corn yields likely instills confidence of at least a trend yield in 2017. Yields have been at or above the linear trend value in each of the past four years, 12 of the past 14 years, and 17 of the past 21 years. Over that period, the U.S. average yield was below trend value only in 1995, 2002, 2010, and 2012. Yield was substantially below trend only in the drought year of 2012, and 2017 weather conditions are clearly not similar to those of 2012.

“More insight about supply prospects for the 2017-18 marketing year will be provided by the USDA’s June 30 Acreage report.” Good says. “However, as in most years, unknown summer weather holds the key to price direction for the 2017-18 marketing year and beyond. Current prices for that marketing year are near the low end of prices experienced over the past eight months and likely reflect expectations of at least a trend yield in 2017. In addition, the price of December futures is below the February projected price for federally sponsored crop insurance products. With the critical part of the growing season yet to come, some continued patience in pricing the 2017 crop still seems prudent.”