When dealing with large farm or companion animals that have died, veterinarians will typically conduct a post mortem on the animal itself to establish the cause of death.
But in the case of poultry, it is not possible to examine every single bird on a farm or in a flock, which is why the selection of birds to be submitted for post mortem is so important. Failure to choose birds that are representative means the vet will be unable to diagnose accurately.
What is a representative sample for post mortem?
The Minster Veterinary Practice recommends selecting six to eight birds per flock, with a flock defined as the birds that share the same air space.
In free-range situations, two flocks may be in different houses, but they may mix in the range. In this case, both groups may be considered as a single flock.
If the problem is mortality, then fresh, dead birds are needed for post mortem. However, for some bacterial diseases, such as erysipelas, it is advisable to submit birds that look sick, either culling them at the farm or bringing them alive into the practice. This will enable the vet to recover the erysipelas, which would otherwise be difficult to isolate due to the rapid overgrowth of other bacteria such as E coli and pseudomonas in dead birds.
In the case of birds with leg problems, a selection of individuals with mobility issues would be adequate.
But when the problem is wet litter, fresh culled birds would give more information to the vet than dead birds – unless mortality is also present. The reason is that motile protozoa and motile bacteria are still moving in fresh culls, which facilitates the diagnosis.
In addition, due to high temperatures in broiler and turkey sheds, the carcasses tend to decompose very quickly, making it difficult to ascertain whether the colour and consistency of the intestines is relevant, or whether it is a post-mortem change.
What information should I provide my vet?
In addition to the number and type of birds that are sent for post mortem, the history of the flock is crucial when it comes to making an accurate diagnosis.
Some of the problems that are diagnosed by vets are not disease- related and may be due to other factors – such as environmental problems, water quality problems, or breakdowns in biosecurity.
The more information that you can provide, the better. The minimum that is required appears in the post mortem submission form. This includes basic details such as the size of the flock, number of houses, type of bird (broiler, layer, turkey), production system (conventional, free-range, barn, organic), sex and age.
Other information that is normally required includes water and feed consumption, level of egg production (if applicable), body weights, mortality rates, number of culls and vaccination programme. There is normally also space for you to describe the reason for the submission.
Also useful is the type of feed that the flock has received – including the type of coccidiostat, if it is present – and any recent changes. In broiler and turkey houses, a copy of the records with the levels of CO2, temperature and humidity helps to assess the quality of the environment in the affected shed.
Finally, remember to write your personal contact details on the form. The vet may have the producers’ contact details in a database, but a telephone number on the submission form always speeds the process.
What other samples are required for accurate diagnosis?
If a viral disease is suspected, it may be necessary to submit blood samples or swabs for PCR testing.
In the case of blood sampling, paired samples are always advised. These are samples collected four to six weeks apart, so that the level of antibodies can be compared.
For PCR testing, swabs need to be taken from different parts of the birds, depending on which virus is targeted. For instance, for infectious bronchitis, the target organs for swabbing are normally the trachea and the cloaca, but other organs, such as the kidneys, may be tested.
For coccidia, worms and brachyspira investigation, faeces samples from different areas of the house may be more appropriate than submitting whole birds for post mortem.
Overall, the type and number of samples that are submitted to the vet or the lab need to be representative of the problem in the flock. If the wrong sample is taken, the cause of the problem may not be found or the diagnosis may be delayed.