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Teaching Farming Animal Science Through Ag Communications


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100 billion animals: What the data say about GE feeds

Photo by keva999 on Flickr

When our assignments were released for this month’s upcoming issue of the Journal of Animal Science, I was excited to take on this particularly controversial topic. Extra caution had to be taken about the accuracy of all the information presented in this article. The Taking Stock editors were very helpful with making sure everything in it was clear and unbiased.

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Genetically engineered (GE) crops are amongst agriculture’s most disputed topics. Their use directly impacts the livestock industry as “food-producing animals consume 70 to 90% of the GE crop biomass.” Since their introduction in 1996, some 100 billion sheep, goats, pigs, chickens, quail, cattle, water buffalo, rabbits, and fish have consumed GE crops.

University of California-Davis geneticist Dr. Alison Van Eenennaam and research associate Ms. Amy E. Young analyzed GE feedstuffs in one of the most comprehensive reviews of its kind. Their paper, “Prevalence and impacts of genetically engineered feedstuffs on livestock populations,” appeared in October’s edition of the Journal of Animal Science. The paper highlights the most significant data compiled about livestock feed, both conventional and non-conventional, over the last 29 years.

“There have been a handful of sensational studies suggesting that genetically engineered feedstuffs cause health problems in livestock,” Van Eenennaam said. “In this review paper we summarize the findings of the large number of peer-reviewed articles that have documented the effects of GE feed on animal health, and also examine the health trends in the large commercial livestock populations that have been consuming GE feed for well over a decade.”

In the United States, 165 crop events in 19 plant species have been approved, particularly plants used for livestock feed. Extensive testing is required before the approval of any genetically modified crop. Internationally accepted guidelines developed by the Codex Alimentarius Commission are followed during the risk assessment of each plant.

Many long-term and short-term studies have been conducted on GE feeds, including ones extending across multiple generations. Of particular significance were comprehensive feeding studies involving an insecticidal variety of GE corn expressing the Cry1Ab protein from Bacillus thuringiensis, commonly called Bt corn.

Results from these comprehensive studies showed that GE feed had virtually the same composition and nutritional quality as its nonconventional counterpart. Additionally, no long-term adverse effects resulted from the feeding of Bt corn. Neither of the proteins unique to Bt corn was found in the blood, organs, or products of animals fed GE corn. As a result, “neither the intact rDNA nor the intact recombinant protein migrated from the digestive system of the animal into other body tissues or edible animal products.”

“Studies have repeatedly shown that the milk, meat, and eggs derived from animals that have consumed GE feed are indistinguishable from products derived from animals fed a non-GE diet,” Van Eenennaam said.

Authors hypothesize that if genetically engineered feeds had negative impacts on the animals consuming them, animal health and performance would decline as a result. To determine this, livestock production statistics were collected from a number of publicly available databases. Analysis of these data showed that animal health has actually increased since the introduction of GE feeds, with lower mortality rates in the poultry industry, lower somatic cell counts in dairy cows, and lower postmortem condemnation rates in cattle.

Another important observation in the review is the very high prevalence of GE feed globally. Countries that are cultivating large areas of GE corn and soy (Argentina, Brazil, and the United States) are the major livestock feed exporters, with the major importers being animal agriculture in the European Union and China. Since the exchange of GE feeds is so widespread, Van Eenennaam says consistent regulation standards are needed in the industry.

“Given there are a large number of GE crops modified to improve their usefulness as livestock feed in the regulatory pipeline, there is a pressing need for international harmonization of regulations to prevent widespread disruptions in international trade of livestock feedstuffs in the future,” she said. “This has already resulted in trade disruptions between countries that are cultivating GE crops and major import markets.”

Read an ASAS press release about this article.

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Capture treat and reuse: Considerations for feedlot water conservation

Here is another review of a JAM symposium I attended.

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Water is the most essential nutrient to any livestock operation. It is also the most precious due to extensive droughts and declining groundwater availability.

Screen-Shot-2014-09-15-at-12.53.20-AM-300x169This highly valued nutrient was the subject of a symposium at the Joint Annual Meeting held in Kansas City in July. During the symposium, Dr. Kenneth D. Casey, Associate Professor of Air Quality Engineering at Texas A&M AgriLife Research in Amarillo, gave a beef perspective on “Water usage at cattle feedlots and the potential for water conservation.”

It emphasized the Texas High Plains region, a particularly dry area where thousands of cattle are raised. He said there is little potential to reduce cattle water consumption itself, so management of other water-using systems is essential.

“Virtually all of the water in the Texas High Plains region comes from the Ogallala Aquifer,” Casey said. “The amount of water there is declining extremely rapidly, and its use is being exhausted economically.”

Cattle can be particularly active at night when it is cool. During times of high activity large amounts of dust are released into the air. Because of these very dry conditions, many Texas feedyards use sprinkler systems to mitigate dust.

“These systems cost many thousands of dollars to install,” Casey said. “In summer conditions, up to 8% of total fresh water use is a result of these systems.”

In winter months, water troughs are set to overflow to prevent freezing. The water spills onto the ground and is “basically a complete loss of water due to evaporation.” Casey says most operations use this overflow method because it involves less maintenance.

“While managing this sort of system is simple, the cost of obtaining and using water will certainly get [producers’] attention in the future,” Casey said.

He says both dust mitigation and water overflow systems need to be reevaluated in a more environmentally friendly context. Several studies have been conducted to compare the cost and sustainability of alternative methods.

“Capturing, treating, and reusing overflow water has been shown to be cost-effective,” Casey said. “The cost to the producer is the same as pumping new water on site, but it is certainly more environmentally sustainable.”

Preserving water for dust mitigation is a more difficult task. Casey suggests careful and regular maintenance, assuring there are no leaks or faults in the system. Overall, it is the producers’ responsibility to conserve their water use for both financial and environmental benefits.

“If you don’t measure it, you can’t manage it,” Casey said. “It’s important to measure, monitor, manage and certainly maintain any water system.”

Read abstract #0434 “Water usage at cattle feedlots and the potential for water conservation.”


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Sulfur in beef cattle diets: A wealth of knowledge and future directions

The challenge with this article was the wealth of information presented in the study. It was difficult to narrow everything down into what seemed to be the most important aspects. However, I found it very useful to ask the authors themselves what they believe to be of particular note in their research…in this case, Dr. Hansen said she wished to emphasize the effects of S on range cows wintered on corn coproducts.

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Outstanding advances in nutrition research continue to give livestock producers the best tools to manage their herds. Of these successful stories, research regarding sulfur metabolism in ruminants has recently been a particular focus “… primarily fueled by an increase in the S content of cattle diets due to inclusions of high S coproducts of ethanol production,” such as distillers grains with solubles, write Dr. Mary Drewnoski and colleagues in a review article appearing in the September 2014 issue of the Journal of Animal Science. The article compiles a vast array of information gained over the last 10 years concerning the impacts of high S diets in ruminants.

Sulfur-induced polioencephalomalacia, or S-PEM for short, is the primary disease associated with excess sulfur intake, and is characterized by swelling of the brain and damage to the grey matter. Even though S-PEM is mostly diagnosed postmortem, certain side effects can be observed in live animals.

“Because of brain swelling, it’s common for animals to demonstrate head-pressing against posts in their pens or become blind,” said Dr. Stephanie Hansen, coauthor and Assistant Professor at Iowa State University. “We’ve even seen animals walk in circles.”

The inclusion of ethanol coproducts in feed rations is a relatively recent practice resulting from the emergence of corn-based ethanol production. Feedstuffs such as dried distiller grains with solubles (DDGS) contain large amounts of sulfur, which poses the threat of S toxicity if fed in large amounts.

Concerns about S toxicity have long been related to high sulfate water, a problem for many locations throughout the U.S. Hansen says high-sulfate water is actually more worrisome than high-sulfate feed because sulfates in water are already solubilized and are readily available for reduction by rumen bacteria. Hydrogen sulfide is then quickly formed in the rumen, which is what causes S toxicity in the animal.

“In contrast, the sulfates found in feedstuffs may or may not be rapidly soluble in the rumen,” Hansen said. “Depending on the protein degradability by rumen bacteria, the sulfate may never break down and be released as hydrogen sulfide.”

Photo by NDSU Ag Communications on Flickr

Interestingly, most research points to eructation as the primary mechanism leading to brain damage. Rumen bacteria degrade sulfide, which is present in the rumen as hydrogen sulfide gas. When the animal belches, it breathes in the H2S, which then travels to the brain.

Fortunately, PEM can be treated if caught early. Thiamine has “nonspecific therapeutic benefits for cerebral diseases,” so it is the primary means of curing PEM.

“A high dose of thiamine will provide a quick energy boost to brain cells to reduce swelling,” Hansen said. “It’s also important to then get cattle off of the high-sulfur diet and onto a more hay-based diet until they recover.”

Brain damage is not the sole problem presented by excess dietary S. If consumed in excess, S can limit the availability of other trace minerals in the diet. For example, S reduces copper absorption through the formation of copper sulfide in the rumen. The copper is then poorly absorbed later in the intestinal tract, which can result in “a mild to severe copper deficiency,” says Hansen.

This pertains particularly to rangeland cattle, whose diets are usually high-forage, but are often “wintered” on feed containing ethanol coproducts in areas like the Midwest. While S toxicity isn’t likely in cows, excess dietary S can drain their trace mineral reserves during the winter months.

“It’s important for producers to know that decreased trace mineral status can have detrimental effects,” Hansen said. “It can result in lower calf health, calf immunity, and cow fertility.”

Other problems associated with high-S diets include reduced dry matter intake and growth, as well as negative effects on carcass quality. “The concentration of S that interferes with trace minerals is likely less than that which decreases cattle performance; however, the effect of S on trace mineral status may be more easily overcome through nutritional strategies than the negative effects of S on DMI and performance,” state the authors in the article.

There are many ways to counter and prevent S toxicity. In terms of high-S feedstuffs, good nutritional management is key. Hansen says it is particularly important for producers to “get a good handle” on the S content of their diets. Additionally, she suggests methods such as monitoring feed bunks well, feeding multiple times a day, and properly rationing of concentrates and roughage.

“Incorporating an adequate amount of roughage in the diet is very important when balancing high-S feeds,” she said. “This slows down the rate at which animals eat and also raises rumen pH. The higher the rumen pH is, the less hydrogen sulfide will be produced in the rumen.”

The review concludes that future research on the topic should focus on “antioxidants as ameliorators of S toxicity.” Hansen says she is currently working with a team researching the negative effects of S on trace mineral status in feedlot cattle.


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Press Releases

Working for ASAS means sharing information about its members and praising them for their work. Talking to them over the phone provided a lot of insight into their research, extension and teaching. Also…more networking opportunities!

Here is a list of press releases I compiled over the summer:

Dr. Leticia Camacho

Bruno Ieda Cappellozza

Hannah Cunningham

Dr. Jean-Francois Hocquette

Erica Lundy

Dr. Melvin Hunt

Dr. Mark Nelson

Dr. Donald Orr

Ligia Prezotto

Dr. Jason Ross

Dr. Timothy Ross

Dr. Eric Scholljergerdes

Dr. Jerry Shurson

Dr. Alison Van Eenennaam

Brian Welly


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Examining biosolids: The scoop on human fertilizer

Photo by normanack on Flickr

Photo by normanack on Flickr

Yet another first…writing about “human manure.” Definitely a lesson in being flexible and open with writing subjects!

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Much like livestock manure, biosolids, or “human manure” is often applied to land as fertilizer. In fact, approximately 50% of all human excrement in the U.S. is spread on various terrains. This is a cost-friendly, sustainable method of sewage disposal, and currently 40 to 50% of biosolids are used as fertilizer in Europe and the United States.

Biosolids, or processed human sewage sludge, are normally treated to remove bacteria and pollutants before they are applied to land. However, some toxicants are resistant to degradation and remain in the treated product. Chemicals commonly referred to as “endocrine disrupting compounds” (EDC), which interact with and potentially alter physiological systems in the body, can be found in both unprocessed and processed biosolids.

Because human fertilizer is often applied to pastures, grazing animals may be affected by EDC in biosolids. If EDC accumulate in the bodies of grazing animals, the compounds could find their way to the human food chain. In recognition of this potential, U.S. and European regulatory agencies have set concentration limits for individual chemicals in biosolids.

However, these regulations overlook the additive effects that could occur when multiple individual chemicals are present. Scientific evidence has suggested that when these compounds are combined they can have synergistic effects even when present at low amounts.

A research team at the University of Glasgow investigated this possibility in a paper published in theJournal of Animal Science.

“The paper [summarizes] the results, to date, of a unique model of real world exposure to environmental chemicals,” said Dr. Neil P. Evans, Professor of Integrative Physiology at the University of Glasgow. “The work highlights some of the shortfalls of laboratory-based studies.”

Multiple studies of sheep grazing biosolid-treated pasture were analyzed. In contrast to studies with laboratory rodents, these studies in sheep more closely reflect human exposure to the range of chemicals found within our everyday environment.

The researchers studied a wide array of physiological systems in the sheep. Overall, they found effects of EDC exposure to be highly variable.

Collectively, EDC exposure yielded more fragile bones than in the control group. Results differed between sexes, but male bone was more sensitive to EDC than that of females. Moreover, fetal bones were relatively unaffected by biosolid exposure in their mothers.

While there were effects on other fetal characteristics such as thyroid weight, testicular development and ovarian development, these changes were not maintained through adulthood.

“Prolonged maternal exposure to biosolids may activate homeostatic mechanisms that protect the fetus,” the researchers wrote.

In contrast, notable changes in the hypothalamic-pituitary axis were observed. The authors also observed “… that early exposure to a cocktail of pollutants, even at very low individual concentrations, can result in alterations in brain sexual development and dimorphism …” These results suggest that EDC have the potential to affect reproductive development and adult reproductive function.

Evans said the variability in results demonstrates the need for further research on the use of biosolids, in part because EDC are widely distrubuted in the environment of humans and animals alike.

“Biosolids [not] used as fertilizer [are] either buried in landfills or burned,” Evans said. “Some of those chemicals return to the earth in rain, so [burning] does not necessarily get rid of them.”

Conducting studies on biosolids is expensive and labor-intensive. One or two compounds can generally be studied at a time, but there are hundreds or even thousands of chemicals present in EDC .

“We need more work on the effects of chemical mixtures,” Evans said. “We know so little [about biosolids] at the moment.”


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Enviropigs: A lesson in transgenic livestock research

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Image by bertconcepts on Flickr

This was perhaps one of the most challenging yet interesting topics I covered. Dr. Forsberg was excellent at explaining aspects of the research paper I had trouble understanding. He also had great insight into the future of transgenic animal research as well as the public’s view of the issue.

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Because they are produced primarily for human consumption, the creation of transgenic crops or livestock is one of the most groundbreaking, yet controversial technologies emerging in agriculture to date. While millions of people consume genetically modified plants every day, genetically modified livestock are not yet approved as part of the food chain.

“It will be quite some time before we see transgenic animals commercially available for human consumption,” said Dr. Cecil W. Forsberg, Professor Emeritus of Molecular and Cellular Biology at the University of Guelph.

Forsberg and his fellow researchers have studied a transgenic line of pigs, called Enviropigs, that were genetically altered to secrete the enzyme phytase in their saliva.

The purpose of creating the transgenic pigs was to reduce the need to add expensive phytase supplements in swine diets, which is needed for optimal nutrition. Like humans, pigs require phosphorus (P) in their diet, but most phosphorus in cereal grains is contained in the molecule phytate, or phytic acid, that is indigestible by non-ruminants. Not only is the phytate P largely unavailable to the pigs, but undigested P excreted in manure can pollute aquatic ecosystems.

The Enviropig line of transgenic pigs, also called the “Cassie” line, was identical to Yorkshire pigs, except that the transgene was targeted to the parotid salivary gland. Previous research trials indicated no differences in the carcass or nutrient compositions of transgenic swine.

In an article published in the August issue of the Journal of Animal Science, Forsberg and his research team addressed, “Phytase properties and locations in tissues of transgenic pigs secreting phytase in the saliva.” The study was developed to examine expression of the transgene.

As expected, researchers found phytase “… present at high specific activity in the salivary glands.” More importantly, the phytase was not expressed in major food tissues (skeletal muscle) or in other tissues such kidney, liver, and skin, and compared with salivary glands only very low levels of phytase were detected in these tissues.

“[This] provides a solid basis on which to conclude that the major food tissues of [the transgenic] and conventional…pigs [have] essentially the same composition,” the researchers wrote.

There are no current trials being conducted with the transgenic pigs. Forsberg said studies on the Enviropig might be revived if scientists develop a way to “stack” other beneficial traits in transgenic swine.

In the meantime, government regulations on transgenic animal research are an enormous obstacle. Forsberg said unless there is a monumental breakthrough, such as the prevention of disease through transgenics, he believes it will be many years before transgenic food animals are commercially available.

“The expense for meeting testing requirements is astonishing,” Forsberg said. “Every tissue of a four-legged animal requires extensive research and documentation.”


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What the data say about Beta-Agonists

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While at JAM, I had the opportunity to attend and report on several symposia. One of the featured sets of symposia surrounded studies where Beta-Agonists were fed to cattle and swine. Here is what I learned.

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Beef and pork producers are well aware of the increasing global demand for their product. They also know their feed and land resources are exponentially shrinking. For them, modern agricultural technologies are a necessity to keep reasonably priced meat on consumers’ plates.

One of these essential technologies comes in the form of beta-adrenergic agonists, commonly referred to as beta-agonists or BAA’s. Beta-agonists are feed additives given to market hogs and cattle to maximize feed efficiency. They work by more effectively converting feed intake to lean muscle growth.

BAA’s come in two forms: Zilpaterol Hydrochloride (Zilmax), used exclusively in cattle, and Ractopamine Hydrochloride, used in both cattle and swine (Optaflexx and Paylean, respectively). Because they so dramatically improve animal growth, the use of these feed additives raise many questions from consumers and producers alike.

“Beta Agonist Symposium: What the Data Say” was held during the ADSA-ASAS-CSAS Joint Annual Meeting in Kansas City on July 20. The Pre-conference was designed to move away from the hype and focus on the raw, clear-cut data about BAA’s. Livestock professionals around the country provided both scientific and industry perspectives on the subject.

Dr. Todd See, professor and Department Head of Animal Sciences at North Carolina State University, discussed live and carcass traits of hogs fed Paylean. His meta-analytic study shows an increase of 12 percent in average daily gain of treated swine. There are also increases in hot carcass weight, 10th rib backfat, loin muscle area and fat free lean at varying ractopamine concentrations. All of this occurs with lower average daily feed intake.

“From a growth and carcass performance standpoint, beta-agonists work,” See said. “[Incorporating Paylean in the diet] produces leaner, heavier-muscled hog carcasses.”

Dr. Ryan Rathman, assistant professor at Texas Tech University, spoke about a similar meta-analysis regarding beef cattle. Zilmax and Optaflexx were compared and had similar effects. Implementing beta-agonist use increased feed to gain efficiency between 15 and 30 percent. He also emphasized a “very impressive” 10 percent improvement in final yield grade of the beef. Stress level was also researched by calculating rates of speed cattle exited chutes.

“We saw that the body is more able to respond to stress, [particularly] early in the treatment period,” Rathman indicated.

Dr. Kendall Karr, nutritionist for Cactus Feeders in Amarillo, Texas, provided an industry perspective on BAA use. Since 2004, Cactus Feeders has fed beta-agonists to over 8 million head of cattle.

He stressed that the U.S. cattle herd has dropped 3.7 million head since 2008. Drought, land use and the high cost of staying in the beef business are all contributors to the decline. Without beta-agonists, Cactus Feeders alone would have to feed 40,000 more cattle per year.

“Beta agonists are very well-researched, safe for people and animals, and conservative of resources,” Karr emphasized. “They are extremely important to the viability of the beef industry.”

Other topics covered during the symposium include muscle fat and biology, carcass transfer and composition, meat color and palatability, and trade barriers regarding BAA-fed swine and cattle. The session closed with a panel discussion by all speakers.