Tag Archives: poultry

The story behind “Light Turkey Syndrome” in Minnesota

Our lab recently published an article in PeerJ describing the succession of the bacterial microbiome in the ileum of commercial turkeys, and the relationship between this bacterial succession and a condition known as Light Turkey Syndrome or LTS. I thought it might be useful to describe the history surrounding this condition in a little more detail.

LTS has been talked about by commercial turkey growers in Minnesota for nearly 10 years. When I first started talking to industry people about LTS, several notable observations surfaced. First, this condition is different than classical disease conditions with known pathology in commercial turkeys. LTS does not involve any known pathology in the digestive or respiratory systems. This is different from a condition known as Poult Enteritis and Mortality Syndrome (PEMS), where there is notable watery droppings in poults, dehydration, stunting, spiked mortality, and acute enteritis. LTS is a benign condition, with only two primary observations that are considered abnormal: 1) high variations in weights between poults within a flock, and 2) lower-than-average flock market weights on the order of 1-3 pounds per bird. 

So, LTS is a problem that is much different than classical diseases seen in the turkey industry over the past fifty years. Dr. Sally Noll’s lab first looked at flocks experiencing LTS to see if there were any notable differences between lighter and heavier birds within the same commercial flock. They first looked for some common gut pathogens, including Salmonella, Campylobacter, E. coli, astroviruses, rotaviruses, and reoviruses. They found no differences between lighter and heavier birds in the presence of these potential pathogens, and they found no differences overall between lighter and heavier flocks for the presence of these potential pathogens. They also did histological analyses of gut and immune tissue and measured xylose absorption on these birds, and found no major differences between light and heavy birds/flocks. To some extent, this ruled out active disease, gut development, and immune status as causes of LTS.

What about external factors? Here are some anecdotal observations. Poults hatched from the same source in Minnesota go to farms within Minnesota and elsewhere in the world. The industry has tracked the market weights of these flocks over a number of years, on farms that have very similar management systems and similar nutritional plans. Based upon an expected market weight established using flocks outside of Minnesota, the vast majority of flocks within Minnesota rarely achieve these weights. 

LTS can be reproduced via inoculation studies. Inoculation of research flocks with fecal homogenates from LTS flocks depresses growth. This suggests something about the gut microbiome that induces LTS. There are a lot of additional refined animal experiments that are needed to fully understand the nature of the gut microbiome-LTS relationship. Is there an unknown bacteria or virus in LTS flocks that asymptomatically depresses growth and performance? Or more likely, is it shifts in the entire gut microbiome that impacts growth and development? Now that we know the succession of bacteria in the turkey ileum and how it is impacted or slowed in LTS flocks, can we modulate it? And is this approach enough to solve the LTS problem?


Salmonella and misinformation?

Every now and then we hear news of potential outbreaks of Salmonella linked to food products. If you have followed the news you will note a recent outbreak linked to raw chicken (an excellent article by Maryn McKenna is here). Many people, including myself, read these articles and then read comments posted below the articles. Comments are great because it connects the public with the author and allows for free discussion. However, I was amazed at the misinformation that is also spread via these forums. I thought it would be worthwhile to revisit Salmonella basics related to 1) cooking and 2) antimicrobial resistance.

1) Cooking. Salmonella are basically E. coli that have evolved to acquire the ability to become intracellular pathogens and cause both diarrhea and systemic disease. However, the basic cellular components between these bacteria are still the same. They are both Gram-negative bacterial cells that do not form spores. Salmonella also do not release toxins like Clostridium botulinum (the cause of botulism) that can kill you even when the bacteria are dead. Therefore, from a foodborne illness standpoint, heat is an extremely effective way to eliminate Salmonella. Cooking meat to an internal temperature of 165 degrees F will ensure that you have zero risk of getting a Salmonella infection from the food itself.

The mistake most people make, though, is in food preparation. The bacteria can be present on raw meat (you should always assume it is). Therefore, separating the “raw” food prep area from the cooked prep area, and washing everything including your hands immediately after dealing with raw product, will substantially reduce your chances of spreading live bacteria to somewhere where they can be ingested. Keep in mind that household pets can also be carriers of Salmonella! If you give your dog raw meat, he/she can then pass the live cells on to the kids that the dog licks five minutes later. Following these basic practices reduces your chances of getting Salmonella from meat at home to very little / none.

It’s also worth noting that regulations are in place to keep Salmonella counts on retail raw meats down. A division of USDA called FSIS monitors the amount of Salmonella-positive samples from live birds and raw meat coming from large commercial broiler and turkey operations. One might ask, “why allow any Salmonella in raw meat products?” A simple answer is that it is currently impossible to eliminate Salmonella from live poultry operations. Birds are an ideal niche for Salmonella because they can carry many of the human-relevant serovars of Salmonella asymptomatically, meaning birds carry the Salmonella in their guts and display no signs of illness. One might also reason that buying organic chicken and turkey is safer than conventionally-raised birds. In fact, there is no difference between these two types of meat, both contain Salmonella along with Campylobacter (example study here). From the time that humans have started raising chickens and turkeys, there has been Salmonella – and that is not going to change anytime soon.

The bigger danger is eating raw vegetable and other foods contaminated with Salmonella. The extensive list of Salmonella outbreaks on the CDC website include foods such as mangoes, cantaloupe, sprouts, nuts, and tomatoes. These present a much greater risk because you may not be cooking these food products. It is advisable to thoroughly wash any raw vegetables and even soak them if possible to reduce your chances of getting infected. Fortunately the presence of Salmonella on these types of food is much less common than on raw meats.

2) Antimicrobial resistance. A final point is that there is major concern about antimicrobial resistance in Salmonella. This is a valid and true concern, as it is evident that Salmonella along with many other pathogens are evolving to become resistant to many therapeutic options available for disease treatment. Fortunately, if you get a Salmonella infection it is very unlikely that you will require antibiotic treatment unless you are infant/elderly. This doesn’t discount though that many Salmonella are now resistant to the most commonly used drugs to treat these infections, and it presents a great risk to immunocompromised populations. Before we jump to conclusions about banning antibiotics from agriculture, though, we probably need to look in the mirror. I have no doubts that all antibiotic use in some way contributes to the emergence of antimicrobial resistant bacteria. However, there are many necessary scientific studies needed to get at the actual risk posed by different applications of antibiotics. For example, which is worse: treating with a very low concentration of an antibiotic not used in human disease therapy for extended time, or hitting with a high dose of an essential human antibiotic for short duration? There is a wealth of literature out there, but even among scientists there still exists debate about this topic. Before jumping to any legislative conclusions, we need more science and data to support these decisions.