[gemy]

I emailed the Skepvet on the study design for Viszlas: Here in is his Here in is his response the bolding is mine.

skeptvet says:
June 20, 2014 at 4:44 pm

The problem with recall bias and with misclassification of different kinds in studies that use similar methods is a well-recognized source of error. It is not something unique to this study, nor does it automatically invalidate the results. However, it is an uncontrolled source of bias that potentially reduces the internal and external validity of the trial. Similarly, the limitation to one breed clearly does reduce the extent to which we can generalize the results to other breeds or mixed breeds. Again, that doesn’t mean the results aren’t worth considering, but it does mean we cannot reasonably use the results of this one trial to dramatically alter our understanding of the risks and benefits of neutering or our specific practices. It is one bit of evidence out of hundreds of studies with its own strengths and weaknesses, and it must be evaluated in that context.
Automatic neutering of all dogs of both sexes at 6 months of age is absolutely an arbitrary practice with little in the way of evidentiary support. The trick is that when we reject such an arbitrary, non-evidence-based practice we be careful not to replace it with another.