What are reasons to be on a LID diet? What are reasons not to use one?
**This is just my opinion**, but I think that feeding a strictly limited ingredient diet to a dog (or any animal) that doesn't require it can ultimately create a finicky digestive system. That has been my observation of different types of animals that I have owned or cared for.
It's not unlike people who never eat spicy food, or never eat high acid food, or never eat beans, and randomly choose to enjoy a dish of such.... bad results. Or people who only drink "city" or bottled water and end up with stomach gurgles if they travel somewhere and drink "well" water.
Different proteins have different types and ratios of nutrients, fats, and amino acids (and of course Taurine, which is enjoying some time in the spotlight right now). In a healthy animal, feeding diversity leads to a stronger system. If you keep animals (rabbits, goats) on dry hay only, and abruptly feed a big bucket of fruit, you're asking for problems. But if they are accustomed to diversity, they handle windfalls or random stuff without issue.
We have one family dog (non-GSD) that actually needs a LID to keep clear skin and nice coat. There are some foods that absolutely do not work for her. With the other dogs, I deliberately mix things up. Again, this is only my opinion, based on my own observations. If a LID is not required
, I would not use one.