Hemorrhagic tracheitis requires attention

Swine producers may be facing an emerging respiratory condition without really knowing about it.

According to Dr. Michael Pierdon with Four-Star Veterinary Services in Pennsylvania, hemorrhagic tracheitis syndrome (HTS) is a clinical respiratory condition that has been identified in pigs that presents with a characteristic gross lesion on necropsy of hemorrhage in the trachea (windpipe) that becomes obstructive. The lesion causes severe coughing and, due to the restricted airway, high mortality.

The pigs develop a hemorrhage underneath the mucosa of the trachea, which creates a “blood blister, for lack of a better term,” that restricts the airway and causes issues with breathing, and ultimately, causes death, he said.

HTS primarily affects growing pigs, with the most dramatic outbreaks occurring in heavier finishing pigs, maybe 125-lbs plus, in Pierdon’s experience. He said he has diagnosed it in younger pigs, including in the nursery, although the severity of the gross lesion is less impressive in younger animals and the mortality doesn’t tend to be as high.

According to Pierdon, mortality rates are in the 1%–2% range. With a sudden acute outbreak of respiratory disease in mid- to late-finishing, with 1%–2% mortality over the course of a week, the losses can be substantial.

HTS is not new, he added, noting that the Swine Health Information Center held a webinar on it in 2020, but it hasn’t gotten a lot of attention because the trachea is not a tissue that is often examined or collected during a routine field necropsy.

The causative agent(s) are also yet to be determined, Pierdon said. “With respiratory conditions, people think lungs. What really put me on the trail of this is finding respiratory outbreaks with severe coughing and high mortality and sudden onset in mycoplasma-negative flows that we would oral-fluid test and find negative for PRRS and influenza.” he said.

While there are really severe lesions inside the trachea, the lungs often do not have significant lesions, he said.

HTS could easily look like influenza, and even that kind of mortality would be typical in an influenza outbreak in late-finishing pigs, Pierdon said, but it’s really telling when there are respiratory outbreaks that test negative for influenza, but those pigs still have those signs.

Clinical management

According to Pierdon, HTS outbreaks should be treated symptomatically with anti-inflammatories and sometime expectorants. He said antibiotic treatments are not particularly helpful given that there hasn’t been a consistent bacterial diagnosis associated with the condition and the affected animals tend to be heavy, market-ready hogs.

He added that it seems to be highly contagious within a barn with symptoms developing over a short period of time (24–72 hours), with the duration of clinical signs lasting 7 to 10 days.

With its rapid onset and lack of definitive cause, Pierdon said it is hard to get in front of the outbreak so it needs to run its course while supportive therapy is provided to clinically manage the pigs through the outbreak.

Critical actions

Pierdon’s goal is to raise awareness of this syndrome or clinical condition as a way of encouraging people to actually open the trachea and look for it. If a barn of pigs experienced an outbreak and oral-fluid samples tested positive for influenza, the assumption would be that it was an influenza case. Pierdon’s hypothesis is that it can’t just be him in Pennsylvania that is finding this problem and he wants other people to know to look at tracheas so those samples can be sent to the diagnostic labs. From there, the diagnosticians and epidemiologists can have more opportunity to try to figure out the actual cause of HTS. If it can be demonstrated that HTS is more common than believed, research funding may become available to further study and understand the problem better.

Pierdon said the lesions are most commonly found inside the trachea between the larynx and the thoracic inlet – in a market hog, about 4 in. behind the larynx. The lesions are most apparent when the trachea is cut in cross-section, he added.

He encouraged swine producers with pigs exhibiting acute and sudden outbreaks of coughing associated with mortality to have pigs necropsied, including an examination of the trachea. Producers can do this themselves or have a veterinarian investigate, but the point is to open the tracheas.

Veterinarians finding HTS lesions should include fresh and fixed pieces of trachea in their diagnostic tissue submissions to the diagnostic lab of their choice for gross diagnosis and histopathology.

By encouraging samples being submitted to diagnostic labs, Pierdon hopes a critical mass of confirmed cases will demonstrate the scope of the problem and make funding available to better understand HTS.

Hot topics in swine nutrition and feed biosecurity

Dr. Jason Woodworth, swine nutritionist at Kansas State University spoke at the Four Star Veterinary Service Pork Industry Conference held in Fort Wayne, Indiana in mid-September about recent nutrition research as well as frequently asked questions.

Gilt development focused on her offspring

“A lot of times we’re focusing on gilt development in relation to her longevity in the herd, as opposed to the impact of gilt development on her future offspring,” said Dr. Woodworth. “We conducted a review looking at factors that influence offspring performance and profitability based on gilt development. This summary table describes the factors to consider when selecting gilts and include birthweight, litter of origin, colostrum intake, etc. The focus is on how to properly develop those gilts to increase the performance and survivability of her offspring.”

Essential fatty acid (EFA) balance

Dr. Woodworth said some of his research is focused on linoleic acid (LA) and alpha linoleic acid (ALA). These types of special fatty acids are found in higher concentrations in vegetable sources and contain much higher amounts of EFAs than other animal-derived fat sources like choice white grease. Research conducted at North Carolina State University studied EFA supplementation to sows and found that when sows go through a typical lactation, their EFA balance decreases. Thus, the amount of EFAs she consumes is less than what she puts out through the milk.

“Net over net, we have a reduction in EFA with some diet formulations currently used. The NCSU data suggested about 125 grams per day of linoleic acid and about 10 grams of alpha linolenic acid per day is the target to maximize performance,” he said. “That’s also in line with a study out of Australia in 2018 that observed reduced piglet mortalities when sows consumed about 120 grams of linoleic acid per day. And a large study we conducted at KSU showed increased piglet weaning weights when EFA were supplemented at increased levels.”

The post-weaning diarrhea challenge

Post weaning diarrhea is an industry challenge in the US. There are three sets of factors that need to be considered.

“From a nutrition standpoint, when we think about post weaning diarrhea, we tend to jump to crude protein pretty quickly,” he said. “We know that when we increase crude protein, a lot of nursery diets will have increased levels of undigested protein going into the hind gut which is helping feed the bacteria there and generating the scours that we’re seeing. The challenge with our mentality of chasing maximum performance, especially in an early weaned pig, is that we also tend to feed excess amounts of crude protein.”

Dr. Woodworth said a change of mindset is needed in our approach to formulate the nursery diet. He recommends a diet with lower crude protein and an amino acid fortified nursery diet spread out over phase one and phase two combination.  He suggests minimizing the inclusion of conventional soybean meal and specialty protein sources while taking advantage of some of the synthetic amino acids.

“The benefit is that it does reduce the incidence of scours, and it also reduces diet cost,” he said. “We need to be thinking about a different target when we approach our performance KPIs for the nursery. Reducing crude protein and nutrient intake may result in lower performance of the pigs, but hopefully it will be associated with less scours which has benefits we see later.”

Another approach to reduce post weaning diarrhea is ABC-4 which stands for acid binding capacity four. ABC-4 isn’t a new concept, but it’s receiving more attention in the US as the industry learns more about the weaning process.

“ABC-4 is important is because a newly weaned pig doesn’t have the capacity to produce enough acid to be able to maximize digestibility of nutrients,” he said. “In the past, we just put acids in the diet. The challenge is that we know some ingredients act as buffers. While we may be pushing some acids in the diet and if we have high levels of limestone, for example, we’re binding them up and those acids aren’t having much of a benefit. So, we started looking at ways to formulate diets to lower the acid binding capacity.”

Dr. Woodworth said nutritionists and producers may be reducing digestibility of some nutrients because the acid isn’t available to break down some feedstuffs. The current push is to figure out how to formulate diets that have low acid binding capacity. Studies are underway looking at ABC-4 and zinc oxide and its impact on average daily gain and removals and mortality.

To summarize, Dr. Woodworth recommends the following to minimize post weaning diarrhea:

  • Reduce excess nutrients like crude protein and feed the right diet to the right pig at the right time
  • Improve digestibility using ABC-4 and enzymes
  • Stimulate gut development with fiber
  • Adjust KPIs to ensure you are aiming at the right target

“The biggest thing is focusing on a whole team approach, especially from a post weaning diet standpoint,” he said. “We can’t do it alone; it takes the whole group. If you’re walking barns with only your nutritionist or only your veterinarian you’ve got a lost opportunity – get the whole team in there together.”

Do grow-finish feed additives make economic sense?

Starting in 2020, the US industry has seen a dramatic increase in fat costs. The rule of thumb of a nutritionist is that a 4:1 ratio of fat to corn price typically allows fat to be used as an energy source. When the ratio is below 4:1, it makes sense to add in some fat, but when it’s higher than 4:1, it doesn’t make sense economically.

“Right now, prices are about 7:1 to 8:1, and so a lot of fat should not be in a diet. However, it may still be there,” he said. “That’s one of the challenges faced by a nutrition supplier. You are often vetted based on your ability to have the best performance. Unfortunately, oftentimes the best performance isn’t necessarily associated with best profitability.”

Dr. Woodworth said the prices agriculture is seeing are not going to change anytime soon, and it’s partly due to the renewable oils push.

“It sounds like the aviation industry is also going to have a big push and initiative to use more renewable oils,” he explained. “What this has driven is, by 2025, to have around 25% more soy crush capacity in the US. Unfortunately for us, the oil will be priced out of our market, but there could be opportunities for lower priced soybean meal as a result of those new crush plants coming online.”

Recent trials assessed the value of added fat (up to 3%) on finishing pigs and showed no change in average daily gain, while 3% fat offered the best feed efficiency. However, the income over feed cost was lowest at the highest inclusion of fat. Dr. Woodworth reminded producers to be mindful of the economics of that decision and measure based on profitability, as opposed to basing it on performance alone.

Consider your feed biosecurity

Prior to the PEDV outbreak about eight years ago, the industry didn’t think much about feed biosecurity.

“We didn’t think about feed being a vector of virus transmission,” he said. “Since then, we’ve learned that viruses like PEDV and even ASFV and bacteria like Salmonella and E. coli can hitch a ride on feed and infect farms. We need to start figuring out how to transfer our sow farm biosecurity mentality to our feed mills and our feed supply chain, because we’re bringing in some of these pathogens through our feed.”

Research has taught us that prevention is the key. It starts with ingredient sourcing and ensuring you’re sourcing from good, trusted suppliers who will do a good job with manufacturing, storage and delivery. He said partner studies with a group in Vietnam assessing ASF transmission showed much of it came down to people in trucks.

“We continue to see with all of our research that getting ASF or other viruses on boots or into truck cabs is really what’s causing some of the transmission issues,” he said. “If we can keep truck drivers in trucks, that’s a big step in the right direction.”

Kansas State University has conducted African swine fever (ASF) research related to feed biosecurity and a summary of the research to-date has shown:

  • While ASF and PEDV are not similar from a virus structure standpoint, they share similar characteristics and behavior within a feed mill
  • Once you bring ASF into a feed mill, it can spread throughout and may be nearly impossible to remove
  • Dust is an excellent carrier of the virus
  • Contamination of feed and surfaces can be detected after multiple batches of feed pass through the equipment
  • Especially with high traffic areas, it’s people who are carrying it throughout the system
  • Mitigants and/or holding feed at different temperatures work to minimize or eliminate the virus

Kansas State University has many swine resources available on their website, including updated Swine Nutrition Guides for producers.

National Pork Board also has resources available to assist producers with biosecurity and foreign animal disease preparedness.

New research on China’s shrinking agricultural land base and what it means for pork imports

Dr. Dermot Hayes, agricultural economist at Iowa State University, shared original ongoing research on the Chinese agricultural market at the Four Star Veterinary Service Pork Industry Conference held in Fort Wayne, Indiana in mid-September.

“The Chinese grain markets are of particular interest in the crop area – how much land they have available,” said Dr. Hayes. “This is a slide showing the value of Chinese imports of wheat, corn, pork, beef, rice, soybeans, poultry, etc. Producers of every one of these products in the US dislikes the China market because the Chinese come and then they go. They come in and buy ethanol and DDGs and then they put duties on that, and then they buy sorghum and then they place a duty on that.”

To any individual commodity market in the US, China has been an unreliable market. However, Dr. Hayes said the chart (below) illustrates that when added together, China’s commodity imports are a reliable growth market. The US just doesn’t know which product they are going to buy.

China was buying pork in 2020, but by the end of 2020 and all 2021, they bought more corn and less pork. He said sometimes they buy products they can substitute like corn and ethanol, using one to make the other. When they do this, it gets political and involves duties. Dr. Hayes bottom line: the import value trend line is going up, and we are seeing about $100 billion in Chinese imports of land intensive products.

“China is driving world commodity prices, even though exporters all over the world really do not like that market,” he said.

Chinese corn imports saw a significant surge in 2020-2021 crop year to about 30 million metric tons. The USDA export estimate for this 2022-2023 crop year shows China is closer to 20 million tons.

“China can only buy corn from the US or Ukraine; they’re not yet set up to buy it from Brazil or Argentina,” he said. “The surprising jump in imports explains why our [US] market started to improve in the fall of 2020.”

Recently, China has been consistent with soybean imports at 100 million metric tons.

“Iowa produces about 10 million acres of soybeans or 12 million metric tons,” said Dr. Hayes. “For one country to buy more soybeans than what the Midwest can produce is quite amazing. Soybeans are the most land intensive crop. This is an economic concept that you can divide goods into land intensive or capital intensive or labor intensive. Almost all the cost of producing soybeans is the acre of land that they are grown on because the seed and fertilizer costs are low relative to other products. What China has done is given up on being self-sufficient in soybeans, they only grow a small amount of domestic soybeans for tofu; all of their soybeans for animal feed are imported.”

Using Google maps, Dr. Hayes shared the images above of the city of Shanghai, China. On the left is Shanghai 20 years ago in 1997 and it’s about 20 miles across. On the right is Shanghai in 2017 and it’s now about 100 miles by 100 miles.

“Shanghai, like the other big cities in China, is located on the land that is the best; that’s how the cities got to be big,” he explained. “If you are out in the desert in China, you couldn’t survive. So, the prosperous cities in China are the ones sitting on good land. The proposition I’m going to set up is how can China claim to have a constant number of crop acres and yet continue to see that kind of growth in their urban areas. It’s not just happening in Shanghai; it’s occurring in Beijing and Tianjin and others. The question is how they are accommodating this rapid growth and urbanization without losing farmland?”

China’s land use policy

“In 2007, an economist in the US wrote a book titled Who Will Feed China, and the answer was – the whole world is going to have to feed China,” said Dr. Hayes. “That scared the Chinese leaders and they said, ‘we’re not going to allow that to happen. We’re going to limit how much crop land we allow for conversion.’ That was in theory, but I’ve been going back frequently and I see more and more land that has been converted.”

According to Dr. Hayes, Chinese leaders, in a typical top-down approach, told the provincial governments that they shouldn’t convert any more land to development.

“What’s different in China is that nobody owns the land itself. The local governments have been making most of their money from converting the land – taking it from peasants and selling it to developers,” he said.  “About 60% of the [provincial] revenue comes from those transactions. So, you can see the central problem. The boss is saying no more conversion of land; but the provincial governments make legitimate revenue from selling communally owned crop land for development.”

For example, consider if every county in Iowa had to report their crop acres to the Iowa state government, and then the state reported those acres into the federal government. The counties aren’t working under any incentive program, so they are reporting accurately that they’re losing land. The state doesn’t want to report their losses to the central government, so about half stopped giving public access to county level data.

“However, the other half continued to publish their losses, which was a mistake, because now we’ve got a look at what they were collecting from the prefecture (like county governments in the US) and what they’re reporting to the Chinese central government. That was an example of what was happening to the land in China before it became political,” he said. “They were losing about 1.5 million hectares (3.7 million acres) a year. Around 2007, it became political, and the government told the provinces they cannot go below a redline set at 120 million hectares, so everyone reported that they were at the redline and not converting any land, which is impossible given what has been reported and what we can see.”

The graph above is from research conducted by Xiaorui Qu, a Ph.D. student who works with Dr. Hayes. The solid line shows China’s claimed crop land. The dotted line above shows where Chinese land now stands based on Xiaorui’s research. China is still losing about 1.5 million hectares a year and they are well below where they say they are. The research estimates China is losing a land base the size of Iowa every decade.

“What does it all mean? It explains the chart showing that China is starting to import a lot of land intensive products,” he noted. “If you ask them, they will say, ‘We are importing corn for a couple of years to rebuild our stocks.’ But the question is, how did their stocks get so depleted in the first place? I think the answer is that if they want to grow wheat and rice to be self-sufficient, then they’ve already given up on soybeans, and I think they are slowly giving up on corn due to the lack of land.”

Dr. Hayes bottom line

“I think US pork exports will resume strong at the end of 2022 and into next year, because of the culling that’s happening in China and Europe,” he said. “I think China will be at import parity for pork going forward, meaning production costs will be at least twice as high and with a 12% import duty, that industry is not protected. I expect to see considerable turmoil in China with considerable imports of pork muscle meat from Europe and pork variety meats from the US. Whether we like China as a customer or not, we’ve got them.”