In all honesty, we don’t really have the full answer to this question. We can however, assume that dogs would not eat their own stool, other dog’s stools and cat poop unless there was a reason. Often the easy answer is that they enjoy it! although this may be a strange concept for most people to accept.
There have been many studies looking for nutritional deficiencies associated with eating feces, but so far, there isn’t any hard evidence to support specific nutrient deficiencies as the cause for eating stools. There is, however, some evidence that this behavior can be acquired when dogs are bored or stressed when home alone or similar scenarios. Still, this doesn’t fully explain why so many dogs show this behavior. It seems that we just have to accept that it occurs and that usually it will not cause too much harm. There are some risks associated with eating feces though. It is a sure fire way of acquiring diseases such as parvo virus and intestinal worms. Cat poop is less likely to lead to disease than dog’s stools but there is still some risk.
So what can be done about this behavior? The easiest solution is to make it impossible for your dog to get to other dog’s stools or the cat litter tray. Walking your dog on a leash is a good start. Put your cats litter tray inside a cardboard box or behind a baby gate to prevent access. There are several products on the market, one is called “Forbid”. It seems to work only for some dogs. Other commonly used tactics are to place a small amount of meat tenderizer on the dog’s food to discourage stool eating. Obviously, this will only work when you are feeding the dog whose stools your dog is eating.
Some people advise adding something like Tabasco sauce to the feces to discourage eating the stool. Hiding the hot sauce by splitting a stool in half and adding some of the sauce inside the stool, then putting it back together seems to work better in discouraging the behavior. But for the dirty work to do this it may be better to just invest in a muzzle or pick up the feces before your dog gets to it.