AvoDermNatural Advanced Sensitive Support Trout & Pea Formula Dry Dog Food 22 lb

Is this the duck or the trout formula? The title states "duck" yet the image and the description of the product say "trout"?

If i wanted to get a different flavor of this would i need to intoduce slowly into their diet?

Why is the trout and pea half off everywhere?

How many cups in a bag?