<human>: Condense the text into a few key points

Hey r/dogs!

I'm looking to start my two 45lb mutts on fish oil soft gels (will likely purchase from Costco). How many mg should be administered per day?

They're fed rotationally on Fromm Surf & Turf/Duckenpfeffer, Zignature Zessential, and whatever decent grain-free kibble I can find for sale on Chewy.

Should I alter how many caps I give them based on the food I feed, or will the food contribution be negligible?

My goal is to see if their slight year-round itchiness subsides as well as to improve the shine of one of the girls' coat. How long might it be before I should notice improvement?
<bot>: How many mg of fish oil for a 45lb slightly itchy/dull-coated dog? Thanks in advance!