Quote: I don't understand what you are saying. What is "weird" to me is that the SAME company considers one type of their kibble(the Adult) to be 5.6oz per "cup" while another type (The Large Breed Puppy) is only 3.6 oz per cup.
Because they are two different formulations--two different "recipes." Peanut butter vs. popcorn is an exaggerated example, but it's the same idea.
The puppy kibble mentioned above weighs less because it is less dense---it either has more air in it, or includes lighter ingredients.
The issue is that a cup is a measure of volume, not weight. It's convenient to talk about kibble in "cups" because it's a handy kitchen measure, but as you've discovered, it is not really meaningful.
Think about it this way--how would you answer the following question: "How much does a cup of food weigh?"
?
Well...it depends. A cup of rice? A cup of grapes? A cup of strained peas?
That's the same issue with kibble. "Kibble" is just a generic word for "food." So if you ask, "How much does a cup of kibble weigh?" You have to know which specific kibble.
Hope this rambling helps a little.