Post-mortem exams help determine mortality causes and which health challenges birds are encountering. But conducting necropsies on healthy birds can also provide the perspective needed to distinguish between what’s normal and abnormal for a particular flock. That’s helpful because cases in the real world are never as clear-cut as in textbooks.
“Doing necropsies is my happy place,” Jenny Nicholds, DVM, Prairie Livestock Veterinarians, told participants of the Canadian Broiler School series. “They can tell you so much about a flock.”
Which birds to select depends on what you want to find out. “Recently dead birds and healthy birds are good options to get a perspective of what’s normal for your flock,” she said. “If you suspect health problems, look for fresh mortalities and sick birds.”
The process can be overwhelming for the layman because it requires investigating unfamiliar territory. “If you’re worried that you don’t know what you’re looking at, that’s OK. If you can recognize normal, you can take photos of the abnormal and talk to your veterinary team to determine what to do.”
Be aware that the most effective outcomes rely on significant preparation before you even cut into the birds.
Required tools
You will need a proper workstation, so set up a designated area and collect the tools before you bring in the birds. Nicholds offers her list of must-haves:
- A flat, clean surface: “This can be a table, or you can flip over a couple of garbage cans and lay plywood on top,” she noted.
- Good lighting: Use a headlamp, flashlight or strong overhead lighting.
- Quality, flexible gloves: Gloves are necessary to protect yourself from possible crossover infection.
- A camera or cell phone: It is best to have an assistant to take notes and photos. “Make sure photos are in focus,” Nicholds emphasized. “Also, show that the abnormality is occurring in multiple birds. For example, take photos of five livers or whatever area is abnormal.”
- A sharp knife, and big and little scissors.
- Cleanup supplies: Wipes, garbage bags and cans.
- Sampling supplies: Swabs, Ziploc bags, containers and a cooler to preserve tissues are helpful to follow up with your veterinarian or send samples to the lab.
Establish the health history
This is a key step. A health history sheds light on what is normal and abnormal for the flock. “The bird never lies,” Nicholds said.
Start with the birds’ age. What are the most likely causes of mortality at this age? “For example, with chicks, bacteria, dehydration, starve outs and failure to thrive are common health challenges,” she noted. “In older birds, there are still bacterial infections but also rickets, coccidiosis, necrotic enteritis and such.”
Next, look within the barn for anything that’s not optimal. “You want to be FLAWLESS,” and Nicholds spelled out those details:
- Feed — Proper access to clean feed that’s aligned to the birds’ age.
- Light — Appropriate for the birds’ age.
- Air/ventilation — The objective is to remove moisture, bring in fresh air and minimize ammonia levels.
- Water — Proper access and a clean supply.
- Litter — What’s the overall condition? Has it been changed recently?
- Employees — Do they understand biosecurity, bird-care and handling procedures?
- Space — Are the birds housed at the proper space and density? Have there been any changes that could be impacting the flock this cycle?
- Sanitation — This applies to between flocks but also within the house. Are there any biosecurity breaches?
Also, look for any recent changes overall. “Is the mortality pattern abnormal? Has anything been added to the water? Have there been any feed changes or a feed outage? Has there been any severe weather?” she added.
Start with the head
Plan to take a consistent approach, following the same process every time you conduct an exam. “That way you won’t miss anything,” Nicholds said.
Start by inspecting the outside of the bird. Look at the eyes, ears, comb, beak, wattles, hock and shank. “We can’t just focus on the inside of the bird,” she added. “You want to ensure there’s no pasting at the vent, no unusual feather loss or skin issues.”
Nicholds recommended starting at the head end for both the outside and the inside exams. “The boring bits,” she noted. “They can be easy to overlook.”
Use scissors to press down on the eye and cut out the lid. Look for conjunctivitis around the eye tissue, and check the eye surface for ulcers, which are often caused by ammonia.
Put the scissors in the mouth to open the oral cavity and look down the esophagus. There may be a bit of feed, but the areas should be clean and smooth. Look for oral ulcers and white spots, which can occur due to high levels of supplemental copper sulfate in drinking water or some mycotoxins. Make note of this.
Next, use the scissors to open the trachea to see inside the upper respiratory tract. This is a critical first line of defense, as the mucociliary apparatus (cilia, or “little hairs”) helps remove mucus that traps particles, allowing the bird to swallow them as it breathes.
“This is known as the respiratory escalator and is especially important as winter ventilation rates decline and ammonia levels rise,” Nicholds pointed out. “If this is damaged, bacteria, viruses or other particles can get deeper into the respiratory system or enter the bird’s abdomen and cause problems, increasing mortality or condemnations at the processing plant.”
If the bird was euthanized, you may observe that it aspirated feed into the trachea. Overall, look for anything abnormal, which can be as simple as having an increased amount of mucus or “slimy gunk” in the trachea.
When the respiratory tract is functioning well, you will be able to see through the air sac membrane. A damaged tract produces a sudsy-looking air sac, which can get progressively worse, even developing a chunky material. There is a three-point scoring system for this.
The brain isn’t a priority unless birds show neurological signs or are gazing skyward. The cerebellum is key for regulating fine-motor skills and should be light pink and smooth. A dark cherry red is abnormal and may be due to vitamin E deficiencies or a bacterial infection.
Consider joints and bones
Before moving on to the body cavity, dislocate the hip/ball-socket joint. If the hip breaks easily, it could reveal bone weakness, arthritis or infection, often called osteomyelitis, Nicholds said.
Examine bones, joints, tendons and legs, and cut into the growth plates. “Broilers are fast growing, but their growth plates aren’t closed yet,” she added. “This is the place to look for evidence of infection or nutritional issues that could contribute to improper bone mineralization and lameness.”
Hold the drumstick bone (femur) and use the knife to cut up toward the line of fat that marks the knee joint. Evaluate the area. There should be some clear fluid in the joint. If it’s cloudy, contains blood or is jelly-like, something is causing inflammation.
“This can be bacterial or viral,” Nicholds said. “Also, if the shank looks thickened or cigar-shaped, that’s a red flag.”
When you cut open the growth plate, note whether it looks normal or thickened. “Broilers occasionally develop rickets, which can show up as a thickened growth plate in the upper area but also can present as a shallow growth plate where the lower zone is thickened,” she noted.
Combinations of calcium, vitamin D3 or phosphorus deficiencies or excesses can cause rickets, impacting the growth-plate presentations.
Check the femur to see that it doesn’t break easily or fold under pressure. This is a good way to test beak strength as well.
Cut into the femur and look for a yellow plug. The long bones grow from a temporary cartilage plate where the bones’ blood vessels deposit bone on that template. “With tibial dyschondroplasia, the cartilage templated doesn’t reabsorb properly,” Nicholds said. “It can create weakness and instability, resulting in pain and lameness.”
Move to the body cavity
Start with the breast muscle. Make a snip in it at the tip of the keel bone, then pull the skin away from the breast to look at the muscle. A purplish discoloration can signal dehydration, but clostridial infections cause gangrenous dermatitis, which can also take on that color. “There’s likely a lot of blood-tinged fluid, and if you push your fingers on this tissue, it might feel like bubble-wrap popping because Clostridium produces gas,” Nicholds said.
If the breast muscle looks greenish, it may indicate necrosis. “If there’s been a weather event or flightiness in the flock with birds flapping wings, it can cause tenderness or necrosis in the deep pectoral muscle,” she noted. “You might not hear about that until the birds go to the processing plant. Look for those changes.”
Follow the lines of fat that run down both sides of the breast muscle. Cut through the ribs and remove the breast muscle and keel to access the body cavity.
The heart is cone-shaped, and if you cut it in half, it should be hard to distinguish the ventricles. “In an abnormal heart, you can see the dilated and oversized ventricles,” Nicholds pointed out. “Some may have cauliflower-type nubbins or cheesy-looking pieces caused by bacterial infections.”
Check the spleen and lungs, which have a bubble-gum coloring.
A normal liver has a mahogany color. It’s worth noting that if the bird was euthanized via dislocation, significant blood may pool in the neck and drain out of the liver, producing a lighter color.
“The liver does all kinds of pathology, so it’s important to recognize if it doesn’t look normal, and then talk to your veterinary team,” she added.
If you find a greenish liver, it may be due to bile buildup. “I try to determine if the bird was lame and wasn’t drinking, causing bile to build up,” Nicholds said.
Chalky white material may be urates, also signaling dehydration. Other abnormal signs are air bubbles, which could be clostridial organisms or viral hepatitis. There may be tumors or granulomas due to a bacterial infection, or fibrin and inflammatory exudate on the liver’s surface.
“We’re seeing a lot more inclusion body hepatitis (IBH), so look for white splotches on the liver,” she added.
Reach in, grab the gizzard and pull it off to the left side. As you do that, look for clear membranes, which will break when stretched. There should be no frothy or chunky bits. Cut the gizzard open; if it’s empty or greenish, the bird is not eating or feeling well. If it’s eating litter, you’ll find it in the gizzard. Also, if you’re feeding whole wheat without the proper supplemental enzymes, you’ll see it in the gizzard.
The digestive tract
Cut into and examine the small intestine, and don’t forget the ceca. “In broilers, we’re worried about intestinal parasites,” Nicholds noted. “They like to live in certain parts of the gut.”
The upper gut/small intestine is the duodenum, where the coccidial organism Eimeria acervulina hangs out. It is one of the few parasites that you can see with the naked eye as little white spots, she added. The oocysts often cluster together.
E. maxima is found in the mid-gut and is a predisposing factor for necrotic enteritis. It doesn’t produce noticeable gross lesions but can cause the intestine to balloon, have a rough internal surface or produce pinpoint blood spots on the outside of the gut. However, other things can cause that as well, Nicholds said. “Veterinarians will scrape this area for samples to look at under a microscope. Severe cases will have bloody contents in the gut.”
At the tail end of the bird, you can find E. tenella. Again, it doesn’t create obvious lesions, but severe infections will cause blood-filled intestines and dying birds with bloody vents.
“Guts are difficult to evaluate in dead birds because birds that die naturally quickly auto-digest versus euthanized birds,” she noted. “So, keep that in mind.”
A note about necrotic enteritis: Coccidiosis isn’t the only culprit. Out-of-feed events, changing feed at the wrong time, inappropriate feed for the birds’ age or whole-wheat diets that lack certain enzymes can also contribute to necrotic enteritis development.
“The most common period for these parasites to challenge birds is 3 to 6 weeks of age,” Nicholds said. “It’s uncommon but possible to affect birds at 2 weeks and highly unusual at 1 week.”
Look at the kidneys, which are long and recessed toward the birds’ backbone. “We don’t see a lot of issues in broilers,” she noted. “Birds with IBH tend to have swollen kidneys. In cases of excess dietary supplementation, such as calcium, we may see urates and stones.”
Finally, look at the bursa. “Think B for B cells, an important antibody factory. The bursa sits past the lower bottom end of the kidneys, at the top of the cloaca,” Nicholds said. “Evaluate this in young birds.”
Final notes
Conduct a post-mortem within 24 hours of death; within 12 hours is ideal. “Cooling down the carcass can help buy you some time,” Nicholds said.
Some companies and veterinary clinics provide post-mortem sampling kits. But it’s important to note that labs will require a veterinary relationship to test samples.
Combining post-mortem exams with necropsies will provide a clearer picture of what’s normal and abnormal through the life stages of your flock. “Understand what the birds look like, and then what you commonly see later through the growing stages,” she concluded. “Consult with your veterinarian. It all will help you determine what to address.”
