Hot summer months present some challenges for diagnosing health problems in pigs. While it’s much more pleasant to perform postmortem examinations in the daylight with temperatures above freezing, it’s also more difficult to obtain good quality samples because of the rapid onset of tissue decomposition.
Most producers are aware of this and have some means of working around the complications presented by the heat. It’s a worthwhile discussion to have with your veterinarian, however, if you are in the midst of working up a particular problem. The chances of coming up with meaningful diagnostic results declines pretty quickly as the pigs begin to decompose.
Following are a few recommendations for collecting good quality samples for laboratory analysis during this time of year:
- Contact your veterinarian early. Because of the race against the clock and the sun, performing necropsies on pigs becomes more urgent in hot weather. Giving notice early in the day helps your veterinarian try to work them into the schedule earlier. That said, necropsies may be held off until later in the day for biosecurity reasons.
- Store the pig in a cool place. The sun certainly accelerates the rate of decomposition, so anything that can be done to keep the pig cool will help. Placing the pig on the shade side of a building or in a central load-out area helps.
- Perform the necropsy and chill the tissues. If you have worked with your veterinarian to learn how to perform postmortem examinations safely, this is the ideal time for you to use those skills.
- Bring pigs to the clinic for necropsy. Some clinics are set up to receive pigs to perform the necropsy at the clinic. Others do not offer this service due to biosecurity or carcass disposal issues. In general, pigs that have more than a hint of green color in the flank are not good quality pigs for sampling.
- Bring pigs to the diagnostic lab. If you are located within a reasonable drive of a diagnostic laboratory, ask your veterinarian to coordinate direct delivery. This is a very good option for having good samples that can be handled well.
- Have your veterinarian euthanize representative pigs for optimum sample quality. If the situation warrants it, euthanizing live pigs that are typical of the condition you are trying to diagnose provides the best samples and avoids the issues of tissue decomposition entirely.
- Fix tissues in buffered formalin as soon as possible. Even with all of the high technology diagnostic tests available, looking at tissues under the microscope is still one of our most important diagnostic tools. We simply can’t learn much from decomposed tissues, so getting thin sections of tissues fixed in formalin as soon as possible is a tremendous help.
- Chill tissues prior to shipping. We can’t expect frozen gel packs to do much more than keep tissues cool during shipment. Therefore, it is helpful to chill the tissues prior to shipping, especially if heads or entire fetuses or piglets are being shipped.
- Ship overnight. Trying to trim costs by two-day shipping isn’t recommended in the summer heat.
- Use extra frozen gel packs when shipping. Increasing the usual number of frozen gel packs is critical during the warm months. Use a 2:1 ratio of gel packs to tissues and ship in Styrofoam insulated boxes.
Jerry Torrison DVM, ACVPM
Minnesota Veterinary Diagnostic Laboratory