They no doubt do use whole dead piglets, but it wouldn't make sense to solely train them that way, IMO. Different body parts decompose at different rates and present different "bouquets" (and even these evolve over time). If a dog could only detect a whole cadaver, it wouldn't be much use in a murder investigation involving a chopped-up body discarded in several locations, for example.
There is absolutely no doubt whatsoever that dogs' noses are probably among the most sophisticated sniffing instrument not known to science.
We all know they work ... science can't give a definitive answer as to how they work and science can't tell us what information the dog is taking in through the nose ... but they are working on it.
There is also the question of reliability to be addressed with some dogs performing well under test circumstances and others not so well ... so until results can be consistent and capable of replication to the highest scientific standard ... an indication will remain just that.
**snip
It would be interesting to conduct a study with a lot of dogs and multiple target scents, with lots of samples for training and, where possible, a real test in the end, with real cows, people, mould etc.
Surprisingly, there are relatively few peer-reviewed scientific studies on the training and use of detection dogs.
Clearly, dogs are used very successfully in several fields without the performance (or publication) of scientific studies.
However, it would be desirable for more rigorous studies to be carried out, particularly on training methods.
In the future, fuller understanding of the canine olfactory sense may mean electronic noses can be created to detect the identity of humans or detect cancer as sensitively as dogs, but even more reliably.
http://stud.epsilon.slu.se/6341/7/blom_m_140108.pdfThe above quote is taken from
Use of dogs as odour detectorswhich was printed in 2013 so is as up to date as possible.