A lot of the arguing going on here would make some sense if genetics was an exact science. It’s not. If it were, we would have seen the last of HD and other health problems generations ago.
To attempt to isolate a simple genetic cause/effect in response to the research question, “what causes bloat”?, is extremely naive.
If there is a suspected genetic component to any trait/disorder, it is more likely than not influenced by more than just one simple genetic mutation that can somehow be removed from the gene pool. Or a mutation that will inherit in some sort of predictable straight line process. These things are multifactoral.
To assume it’s possible to exclude the impact of environmental influences also makes no sense.
Dogs don’t live in isolation tanks.
Part of conducting a valid study requires controlling for as many extraneous variables as possible. If your subjects are dogs living in home environments, there will be a nearly unlimited number of extraneous variables for which you can’t control.
The study can control for things like breed, age, size, and general health, along with what’s known of the ancestors. But, then you’re doing breed specific research. How do you then generalize that to the total dog population?
To simplify; you always begin a research project with a research question. When it’s one as big as “what causes bloat”, or “is bloat genetic”, the difficulties is setting up your study are legion. (Actual research questions are typically much more refined, of course); unless your subjects live out their lives in research labs under tightly controlled circumstances.
Any study of bloat will have to be longitudinal. No valid conclusions can be reached unless the subjects are followed throughout their lives.
Again, there is no way to control for all of the variables that will impinge on the subjects outside of the lab setting.
The only way to counterbalance this effect is via replication studies. And, you certainly want to look for large sample sizes.
Not all studies are created equal.
Again, it’s telling, but, not surprising, that after nearly 30 years of research, there is still no firm conclusion from the people who actually understand what they’re talking about.
Because of the speed with which technology is advancing, we will probably know a lot more in the near future.
None of this should be construed to suggest that bloat does not have genetic components. I would offer that many factors about any individual dog that are heritable make certain dogs more bloat prone.
Ideally, researchers will ultimately identify the combinations of genetic and environmental factors that set up the highest risks that whatever genetic mutations may be involved are most likely to manifest. Once we know that, breeders can incorporate the information into their breeding decisions.
The takeaway should be that when you examine a phenomenon as complex as bloat, there is no simple genetic on/off, yes/no switch.