If the poo was ok on the grocery store brand, you need to go back to that and get her stabilized before trying to introduce another new food. The large poo means she is not digesting the food properly which may or may not have anything to do with fiber. It probably has more to do with totally new ingredients, higher protein and fat. Look at the bag of the grocery store food and compare protein, fat, and fiber to the Wilderness food. Unless you get a limited ingredient grain free food, most are not as easily digested as the grain inclusive brands. If you want better food, go on Chewy and look at the ingredients, protein, fat and fiber in other foods and find one that is closer to what she is doing ok on. If you want to try a grain free food to see how she does, then choose one with very limited ingredients to start, such as Natural Balance or Wellness Simple.
