There is no universal panacea to prevent cannibalism. I also hope that from the above you realize that adding salt to water or feed, while sometimes preventing cannibalism, is a very erroneous approach to the problem. This is assuming that the feed already contains the proper amount of salt. In that case, by adding salt you only create additional stress and you are not removing the primary cause of the problem. Once blood is drawn on a large scale in the flock, other birds join in as they are all carnivorous at heart, but this is secondary.
Cannibalism can be a simple or a very complex problem.
Bright lights, sharp beaks and overcrowding are the main causes and can be dealt with separately or collectively. Reduce light intensity by reducing the sunlight effect or by dimming the artificial light or reducing effect of light colored walls. Beak trimming is a good idea and using an anti-peck paste on birds may be helpful. Giving more room to the birds will definitely be an asset. It must be remembered that the cause has to be removed to get results.