Recent research shows salt helps cattle avoid death as a result of grass tetanyWritten by Heather Smith Thomas
The cause of grass tetany or grass staggers has been poorly understood, yet annual death losses cost stockmen millions of dollars. It affects mature cattle grazing lush forage, after weather changes like freezing early spring pastures or sudden growth after rainfall following drought.
This disease is associated with magnesium deficiency, calcium deficiency and excess potassium in the blood of affected animals.
During cool, wet conditions or regrowth after frost or drought damage, sodium levels in certain forage plants plummet, while nitrogen and potassium levels spike. Recommended prevention has been supplemental dietary magnesium, and many producers feed high levels to try to prevent losses.
Standard treatment for acute cases has been to administer oral and/or intravenous magnesium.
After examining cattle lost in 2001 following spring frosts in the Midwest, Thomas Swerckzek, a veterinary pathologist in Kentucky, found clues about the cause and prevention of grass tetany.
A few years earlier, he had collaborated with William McCaw, a veterinarian working with several purebred herds, trying to find answers to some of their health problems.
When Swerckzek started looking at herds, he found one farm with very healthy Hereford crossbreds. The owner was feeding loose salt rather than mineral mixes. Most farmers in that area fed mineral mixes and salt/mineral blocks, and cattle often over-ate the mineral mixes to get the little bit of salt in them.
The farmer with the crossbred cattle had a salt house in every pasture.
“He wasn’t feeding any magnesium. He’d been in the cattle business more than 40 years and had never had a case of grass tetany,” says Swerckzek. “This was a hint that maybe it wasn’t necessary to feed magnesium to prevent grass tetany.”
Swerckzek continues, “Later, when I got several herds off the mineral mix, they quickly started to turn around. Most of the cows had been suffering from diarrhea and wasting away, and within 24 to 48 hours they improved, after giving them plain loose salt instead of mineral.”
At the time, Swerckzek was working with a herd of about 1,000 Angus and driving through that farm with the manager.
“We came across a cow that had been down for several days in spite of multiple treatments with magnesium and calcium,” he says.
Swerckzek had some sea salt and put it in front of that cow. Three hours later, she’d gotten up and wandered off before going down again. The manager put more salt in front of her.
By the next morning, she’d gotten up and rejoined the herd.
There were other cattle in the herd showing signs of grass tetany and going down.
He mentions, “I told the manager to put a handful of salt in front of them or get it into their mouths. Those cows came out of it.”
“We had massive losses in Kentucky one year due to an unusual winter with many warm spells. Grass and clover grew early. Then we had a hard freeze in April. Cattle went down by the thousands with grass tetany and bloat. People were using bloat blocks but this didn’t help because they didn’t have salt,” he explains.
“The same thing happened in 2010. We had a lot of clover, and the farmers using bloat blocks said their cows were eating them like candy, and it didn’t help. The farmers who had salt out didn’t lose cattle,” says Swerckzek.
Reasons for tetany
“The reason cows go down with grass tetany is that they are short on magnesium and calcium, but I didn’t know why salt worked,” Swerckzek says.
Then, he discovered a connection between grass tetany and nitrates.
“We’d been taught for many years that nitrate is not toxic – that nitrite is the problem. In the 1940s when nitrate was discovered as the cause of cornstalk toxicity, it was nitrites causing shortage of oxygen in the blood. But I found that nitrate is 100 times more important in grass tetany than nitrite,” he says.
The body must get rid of the nitrate, and it does this through cations, especially sodium.
“When there isn’t adequate salt in the blood, the body grabs onto the most available cation, which would be magnesium and then calcium,” he explains.
When the spike of nitrate occurs – when the cow consumes frost-damaged forage – her body immediately uses magnesium in the blood to combine with and get rid of the nitrate, which depletes the body’s magnesium, which is why the cow goes down.
“If there’s enough salt available, the body can grab onto the sodium and cows don’t go down with grass tetany or milk fever,” he says. “If they don’t have salt on the day this hits, they go down. It has to be there all the time, and it can’t be hard salt blocks because cattle can’t eat enough when they suddenly need it.”
Potassium and sodium
Another piece of the puzzle fell into place after Swerckzek found that on some farms, even though farmers supplied salt, cattle weren’t eating enough of it.
Potassium levels in grass were spiking to levels 15 times higher than normal after hard frost, especially when it was lush and highly fertilized.
“Since the cation potassium and sodium are so close together, these minerals can substitute for one another. When potassium spikes, even though cattle have salt available, they won’t eat it because the body thinks they already have enough,” he explains. “They are actually sodium-starved, but their bodies didn’t know the difference between an excess amount of potassium and too little sodium.”
The body usually has the ability to keep sodium levels within normal range, but when it drops lower, ranchers may only have a few hours before that animal dies.
“If we feed salt, however, and the animals eat it, they’ll be fine as long as they have plenty of water,” Swerckzek says.
British scientists in the 1930s noticed that salt could prevent grass tetany, but no one put it all together until Swerckzek figured it out.
Antibiotic Resistance - Scientists look at feedlot bacteria to study resistanceWritten by Natasha Wheeler
Lingle – “The big question my group tries to answer is whether or not antimicrobials in livestock cause or contribute to antimicrobial resistant infections in humans,” stated Noelle Noyes, a PhD student at Colorado State University (CSU) Veterinary Teaching Hospital.
Noyes and other scientists gathered at the University of Wyoming James C. Hageman Sustainable Agriculture Research and Extension Center (SAREC) in Lingle on Sept. 10 for the High Plains Nutrition and Management Roundtable to share their recent findings concerning livestock issues.
“This is a very contentious topic, and it gets sensationalized in the media,” noted Noyes.
Human resistance to antibiotics is often blamed on sectors of agricultural production, inspiring Noyes and her team to investigate how bacterial genetics change throughout a feedlot system.
“Typically, when we do surveillance for resistance in livestock, we use a so-called indicator bacteria. This might be a non-type-specific E. coli or Salmonella, for example,” she explained.
The indicator bacteria are isolated and tested for resistance to a particular drug.
“This becomes a little bit suspect when we think about the ecology of where bacteria are actually living,” she stated.
To illustrate her point, Noyes shared a pie chart depicting the thousands of different bacteria present in the environment.
If scientists are only looking at one kind of bacteria instead of all of the different strains, Noyes mentioned, “We may get a really biased picture of what is going on.”
Thanks to new technology, scientists are now able to look at the bigger picture using equipment called Generation Sequencing Machines.
“This technology is becoming very widely available and widely used by different groups. I think it’s important to understand the technology and understand the types of results that we get from it so we can respond to results appropriately,” she continued.
To use the technology, scientists collect samples from soil, water, feces, surfaces or rinsates. All DNA is then extracted from the samples, fragmented into small pieces and catalogued in a library.
“The sequencer reads through all of the little fragments and spits out a file that tells us the DNA sequences of all of the fragments,” she said.
Those sequences are then compared to a catalog of known resistance genes.
“It’s a little more complex than that, but basically, that’s what happens,” she noted.
Noyes and her team have conducted a number of studies using the sequencer, but she focused on two of them in her presentation at the Roundtable.
“In the first study, we went into four feedlots, gathering data from two pens per feedlot, and we followed the cattle from the time they were placed to the time they were shipped,” she explained.
Bacteria samples were collected at various time points from the pens and transport trucks. Samples were also collected from the surface of chuck and round conveyor belts after the cattle went through the slaughter and fabrication process.
“There were 88 samples total, representing 11 per pen across each of the time points,” she stated.
Once the samples were processed, 4 billion DNA fragments were produced, and 1.2 million matched an antibiotic resistant sequence.
“This is where we start worrying about people saying that we found millions of resistance genes in the samples,” Noyes commented.
Although there were millions of resistant genes throughout the samples, many of the DNA sequences were the same. Ninety-five percent of the resistance applied to only two drug types.
“We only identified 319 actual resistance genes,” she explained.
As a side note, she added that no bacteria with resistance genes were found in samples from the slaughter or fabrication process.
After analyzing and graphing the data, Noyes noted, “We are seeing that cattle arrive in the feedyard with a different resistance composition than when they leave the feedyard.”
Also, there appear to be more strains of resistant bacteria when the cattle arrive at the feedlot than there are when they leave.
“This is indicative of selective pressure,” Noyes said. “Only certain bacteria survive and flourish.”
These findings are leading to further research as scientists are still unsure why certain bacteria survive and others don’t.
“There are a lot of other things going on during the feeding period. The cattle are being moved, their diet is being shifted, and they are all coming into one area. A lot of things could be affecting this change,” she commented.
In the second study that Noyes discussed, two pens of commercial cattle were studied over an 11-day period at a feedlot. One pen of cattle received the drug Draxxin, and the other did not.
“There was no difference between the treatments,” Noyes stated.
Results from the second study paralleled results from the first study, indicating that cattle arrived at the feedyard with a greater variety of antibiotic resistant bacteria than they had when they left.
“The take-away is that the transition into the feedlot does have a huge impact,” Noyes commented, adding that further research will be needed to learn more about how that information applies to animal and human health.
“Antimicrobial resistance is really complex,” she remarked. “There are a lot of places where antibiotics are used, and there are a lot of places where people can pick up resistant genes.”
Noyes is hopeful that the new technology will help scientists get a better idea of how bacteria interact and react to their surrounding environments.
“We are looking at these resistant genes as if they are all the same but different genes carry different risks to human health. We need to start coming up with a way to know, when we see these changes in a feedlot, if they are more or less risky. We don’t know yet,” she said.
AES recognizes top researchersWritten by Saige Albert
Laramie – During a Feb. 18 banquet, University of Wyoming’s Agricultural Experiment Station (AES) held it’s 2015 Research Awards and Appreciation Banquet in Laramie and hosted a full room of Extension personnel, College of Agriculture and Natural Resources faculty and staff, University of Wyoming officials and community members.
The event recognized the winners of the Early Career Research Award and the Outstanding Research Award, as well as those researchers with papers to be published in the College’s Reflections magazine.
“The Agricultural Experiment Station has been doing what it does for a century and a quarter,” said UW President Richard McGinity in his opening remarks. “That is really something.”
McGinity noted that AES was established in 1891 to conduct scientific research to advance agriculture and the state’s rural communities.
“AES continues to conduct ag and applied research on agriculture, natural and community issues related to the needs of Wyoming, the region and the world,” he said.
College of Agriculture and Natural Resources Dean Frank Galey continued that the mission of a land-grant university is three-fold, including teaching, research and Extension.
“Research is so critical for everything we do at a land-grant university,” Galey mentioned, noting that the researchers recognized during the banquet, as well as many others throughout the college, are producing a high standard of research.
The Outstanding Research Award is presented to an established researcher in the College of Agriculture. The winner is recognized on a plaque in the AES Hall of Fame and receives a $1,000 award.
This year, Scott Miller was recognized for his work.
John Tanaka, head of the Department of Ecosystems Science and Management, noted, “Dr. Scott Miller came to UW in 2002 as an assistant professor in the Department of Renewable Resources, which is now Ecosystems Science and Management. His research focus is special hydrology.”
Miller pursues research in innovative field and modeling techniques to better understand the transport of water and how humans change the hydrologic response.
The Early Career Research Award also received a $1,000 prize and recognition. Dan Levy of the Department of Molecular Biology received the award for his work on nuclear sizing.
“Dan has a remarkable background in science,” said Department of Molecular Biology Head Mark Stayton. “He joined us in August 2011 as a new assistant professor.”
Prior to joining the University of Wyoming, Levy worked at the University of California – Berkeley on questions of nuclear size and its relation to health, which inspired the research he conducts today.
In his three years at UW, Levy has published nine papers and secured over $2 million in direct research funding.
“The competition was extremely tough in this category, and all of our nominees were extremely deserving,” said Bret Hess, associate dean and AES director.
Each year, UW College of Ag faculty and students submit papers to be published in the research magazine Reflections. Each department elects a representative to draft a paper on behalf of their department for the magazine.
The top paper is recognized with a $1,000 award. In addition, the department from which the research originated from also receives $1,000.
With their paper titled, “Collaboration across continents: Predator compensation policies in the U.S. and France,” Ben Rashford, Tom Foulke, Jordan Steele and Tex Taylor won the honor in the Department of Agriculture and Applied Economics.
UW College of Agriculture student Anna Scofield was also recognized as being the only student to have a paper published in the magazine.
Also during the banquet, AES recognized the work of one employee who went above and beyond in working at UW AES.
Jeremiah Vardiman signed on as the research associate at the Sheridan Research and Extension Center in 2009. As the center expanded and developed due to generous donations, Vardiman continued to accept the challenges associated with the facility.
Vardiman recently moved to Powell to serve as an area Extension educator.
McGinity said, “We have more opportunities than we can take advantage of. The College of Ag and AES is the role model for the outreach that the university really needs to make all across the state.”
“The work going on here is world class, and the people here are world class,” he commented. “The future of the College of Agriculture – and the rest of the university – is bright.”
New research shows faster growing cattle at higher risk for brisket diseaseWritten by Gayle Smith
When cattle producers started PAP testing bulls for high altitude disease, they thought the disease would eventually disappear. However, as researchers dive more into this disease, they are finding it is more complicated that they first thought.
Brisket, or high altitude disease, is pulmonary hypertension that occurs when there is increased pressure in the pulmonary artery. The pulmonary artery takes blood into the lungs to get oxygenated. When cattle have high altitude disease, blood backs up in the venous system causing fluid to build up. This causes brisket edema, mandibular edema or belly draggers in cattle.
When cattle experience pulmonary hypertension, the right side of the heart vessels narrow or constrict causing congestive heart failure, if it gets bad enough.
According to Colorado State University (CSU) veterinarian Frank Garry, brisket disease is not unique to high altitude.
“When it occurs at high altitude, it is because high altitude creates the problem,” he said. “That’s when it's called brisket disease at high altitude.”
Discovering brisket disease
This condition was first discovered in Colorado over 100 years ago when some South Park ranchers asked CSU researchers to determine why their cattle were dying.
“Over the next 30 to 40 years, we determined why it was occurring and developed the Pulmonary Arterial Pressure (PAP) test, which allows us to detect the problem. By 1960, we had determined the pathological pathway,” he explained.
Low oxygen in the environment at high altitude causes the bovine lung to respond to the high altitude by constricting the arteries.
When the arteries are constricted, it puts pressure on the heart, Garry said. Changes in the arteries lead to narrowing of the blood vessels, putting increased pressure on the right side of the heart.
“Some animals do okay with pulmonary hypertension over long periods of time,” he said. “Others will succumb to right side heart failure and brisket disease.”
At one point, scientists told producers to select bulls that, at a high altitude, have low pulmonary pressure for this moderately heritable trait. But it wasn’t enough.
“We don’t dig ourselves out of a reproductive problem by just breeding,” Garry said. “It takes generations of time. We thought that if producers bred their cows to low PAP bulls over time, this problem would just go away.”
What they have found is brisket disease is a progressive condition.
“We have producers who have been testing bulls for 30 years and still have problems with this disease,” Garry explained.
When one of these producers started reporting problems with what he called “summer pneumonia,” Garry sent one of his graduate assistants to investigate. Utilizing producer surveys, pathology and physiology, Garry said his graduate assistant was tasked with finding out if these calves were actually succumbing to summer pneumonia.
“At first, producers thought they just had a toxic plant problem, which they quickly found was not the problem,” he said.
The cattle had more problems with pneumonia and pulmonary hypertension.
Ranching at altitude
“High altitude ranchers face more liability,” Garry said. “It is a tough environment for the cattle to grow up in.”
After performing necropsies on as many calves as possible that summer, it was determined that half had died from bovine respiratory disease (BRD) and the other half from pulmonary hypertension.
“These calves didn’t look like belly dragger calves or calves with classic brisket disease,” Garry said.
Identifying brisket disease
The calves did show higher levels of oxygen stress than researchers had anticipated, which showed that brisket disease is not just a high altitude problem.
“The clinical signs are so similar to pneumonia that it is hard to distinguish between the two, particularly in the early clinical stages,” Garry said. “However, the diseases look different histologically.”
“We have initial evidence that the cardiopulmonary system is undersized for the oxygen requirement,” he continued. “Cattle get different pulse pressure. Blood doesn’t circulate as well at high altitude.”
At this point, PAP testing bulls is still the best tool available to address the disease.
“Brisket disease is increasing in the cattle population, regardless of altitude,” Garry said. “If a producer suspects summer pneumonia, it is really important to get a veterinarian to do a necropsy.”
“It is important to know if we’re are dealing with infectious pneumonia or pulmonary hypertension,” he said.
Garry fears cattle producers are dealing with a similar problem that affected the broiler industry years ago. Broilers were dying because they had been bred for too fast of a growth rate. It makes a difference how cattle are bred, where they are raised and where they go to the feedlot.
Garry said in Nebraska feedlots at 3,500 feet, nearly-finished cattle were dying from high altitude disease that had never been above 4,000 feet.
“Death loss attributed to heart failure in three northern Colorado feedyards in 2014 accounted for 7.1, 9.9 and 6.5 percent of the moralities,” Garry shared. “Management and breeding both figure in to this problem. It is not caused by a single trait.”
The problem may be with the cattle growing really big, really fast. The average live market weight has increased 48 percent since 1944.
“The risk of dying from heart failure has doubled in the U.S. and Canadian feedlots since 2000,” Garry said. “There is a tendency for feedlot cattle to die from heart failure later in the feeding period.”
Cattle pulled and treated for bovine respiratory disease were also found to be more likely to die from heart failure.
Garry said the bovine lung has a decreased alveolar surface area in proportion to body weight, and the cardiac mass, as a proportion of hot carcass weight, is smaller than almost a century ago.
“If we breed fast-growing cattle, we should expect this to continue to be a problem in the feedlots,” Garry summarized. “My recommendations are to PAP test cattle and be aware that if we’re at high altitude and breeding for excessive growth, we are putting cattle at increased risk for physiologic stress. Do things to prevent infectious disease because those diseases cause inflammation, and the combination of these things causes this problem.”
It is important to test yearling bulls before purchasing them for high altitude cattle operations. If the bull tests high at a low altitude, don’t purchase it, Garry said. If the bull tests reasonable at a low altitude, retest it at a high altitude before purchasing it.
Expected Progeny Differences help producers determine economical selectionsWritten by Natasha Wheeler
“It is critical to concentrate on traits that are economically relevant to our breeding objective,” notes Matt Spangler, Extension beef genetic specialist at the University of Nebraska–Lincoln.
When managing expected progeny differences (EPDs) in cattle, producers should consider how various traits relate to one another.
“More isn’t necessarily better,” Spangler explains, using milk production as an example.
In a study from the early 1990s, researchers looked at how milk production correlated to the economic efficiency of calves marketed at weaning and harvest.
“Milk production, especially in environments where feed availability is limited, can be a detriment,” he says.
Lactation potential correlates with increased costs for nutritional requirements, Spangler adds, noting that to achieve high milk production, cows require more feed.
“Even when cows are dry, they require more nutrients due to lactation potential because their visceral organ size is larger,” he explains.
Cows that utilize resources for heavy milk production may not do as well maintaining body condition or fertility.
When considering EPD scores, Spangler notes, “Important maternal traits include female fertility, maternal calving ease, maintenance requirements, longevity, maternal weaning weight, disease susceptibility, regional adaptability and temperament.”
Most breed associations maintain scores for all of these traits, except for disease susceptibility and regional adaptation.
“In terminal sire selection, I consider important traits to be calf survival, male fertility, disease susceptibility, calving ease direct, growth rate, feed efficiency, carcass quality and composition,” he adds.
Although EPD scores are generally not yet available for calf survival and disease susceptibility, they are significantly impacted by crossbreeding.
Spangler explains that producers should also consider environmental factors when selecting animals for breeding.
“Phenotype, or the outward appearance of an animal, is really the sum of genetic effects plus environmental factors,” he says.
This means that two animals can reach the same statistics, but in different ways. For example, two calves can reach the same weight at weaning, but not be identical.
“One calf may get there through superior genetics, while the other may get there through an advantage in the environment,” he explains.
This is important to remember when selecting sires, because the visible, physical traits of a bull may not tell the whole story.
“As we choose sires, we have to realize the only advantage the sire passes on to the next generation is through his genetics, not through the environmental benefits he may have been afforded,” he comments.
To learn about which traits are genetic, researchers and producers analyze an animal’s progeny.
“We get an average for a sire’s calves, compared to their contemporaries,” Spangler states.
These data points become the foundation for EPDs, which are then valued by their expected accuracy.
“We shrink EPDs according to our belief in them,” Spangler says. “In a high accuracy sire, EPDs wouldn’t be shrunk much because we have a very high degree of belief in them. A low accuracy sire, where there is considerable uncertainty, will be shrunk more,” he explains.
From there, producers can use scores to determine values such as input traits for their operation.
Spangler illustrates this, saying, “Angus’ dollar energy value on milk and mature size EPDs give producers a feel for which bulls may sire replacement females that may be lower cost.”
Red Angus’ maintenance energy EPD is another example. It focuses on mature weight that is corrected for body condition score, highlighting the maintenance component of milk production.
“These two tools can be used for producers who really need to get a handle on decreasing input costs in a cowherd,” he states.
There are also EPDs that focus on measures of reproduction.
“We know that fertility is at lease twice as economically relevant as either growth or carcass traits,” he comments.
Several breed associations also publish heifer pregnancy and stayability EPDs. Stayability data refers to the reproductive longevity of cows.
Calving ease is also measured.
“There are two types of calving ease – calving ease direct and calving ease maternal,” he continues.
Calving ease direct refers to a sire’s impact on his direct progeny. Calving ease maternal refers to the ease of the calves produced by his daughters.
“It’s important to select for both of those EPDs if producers are retaining replacement heifers,” he adds.
Spangler concludes that selecting for traits should maintain focus on economic relevance to the operation.
“EPDs are seven to nine times more effective for creating change than selecting on actual measurements alone,” he says.
“Unfortunately, EPDs are specific to a breed, and we can not directly compare EPDs of different breeds against each other,” comments University of Nebraska-Lincoln Extension Specialist Matt Spangler.
To compare across breeds, producers can find across-breed adjustment factors, which are published annually by the U.S. Meat Animal Research Center (MARC).
“These can be used to adjust EPDs so we can get a fair comparison across breeds,” he notes.