Thoughts on ALS versus Large Breed kibble

Fat is the main energy source in dog diets, and so it's very normal for kibbles with a higher fat percentage to require smaller serving sizes - they need to eat less of it to meet their caloric needs. In the case of complete diets like most kibbles, any serving large enough to meet a dog's caloric needs is going to meet the rest of their nutritional needs as well, even if it's smaller than the recommended serving size for their weight (which it almost always is - most recommended servings on dog food are on the high end for most pet dogs).

As for whether you'd be feeding more fat total with the Large Breed vs. the ALS in that case, you do have a little hiccup with your decimal placement of the percentages. It should read: 3.625 cups food * .13 = 0.471 cups fat a day, and 4 cups food * .145 = 0.58 cups fat a day. So you'd still be feeding more fat daily with the recommended portions of ALS food, even though they're smaller. However, it's worth remembering that these percentages are only minimums, not exact numbers as it's easy for macronutrients to vary slightly between batches of food, so it's good to avoid getting too caught up in the exact numbers.

I hope that helps clear things up a bit. I personally don't try to get too bogged down in the numbers when it comes to complete, commercial diets following AAFCO (or similar) guidelines (obviously the exceptions are when trying to manage a medical condition with food or balancing a homemade diet), and mostly evaluate what brand/amount is working based on how my dogs look, feel, and behave. Saves me a lot of stress, because it's easy for me to get caught up and freaked out over minutia when my dogs are actually doing just fine.

You're right, my bad there! Yeah, you'd be giving slightly less fat in that case, then, but it's still unpredictable due to those numbers being guaranteed minimums only and not 100% accurate all the time. The math is one of the reasons I try not to get bogged down in the exact numbers, haha, I understand how to do the equations in theory but find it really easy to lose track of the numbers themselves.

The only issue I know of with calcium for large breeds is in regards to growing puppies, because it's especially important that they don't grow too quickly so their bones and joints develop properly, so some puppy foods with too much calcium (or a poor calcium to phosphorus ratio) aren't appropriate. I am absolutely not an expert on large breeds (or dog nutrition in general) though, so take that with a grain of salt!

I have done homemade raw diets before, and honestly the convenience of having a brand that's already been tested and approved as following guidelines set by reputable organizations (like the AAFCO mentioned) is that you can have the confidence that, insofar as we understand dog nutrition and health at this moment, they will not cause deficiencies or imbalances or result in disease due to the food alone. Of course certain dogs are going to have allergies, intolerances, medical conditions, etc. that can make certain foods inappropriate or even dangerous for them, and of course we do not know everything about dog nutrition and health there is to know (heck, we don't even fully understand human nutrition). That's why there's no such thing as one 'best' dog food/diet, commercial or otherwise, and why it's important to listen to your dog and adjust your feeding if there's signs that the food (and/or portion size) isn't working for them. But in general, it's extremely rare that a commercial, complete kibble that meets modern nutritional standards is going to make an otherwise healthy dog who's tolerating the food well sick due to imbalances/deficiencies.

Currently I do like to swap foods every bag or two, mostly because I feel my dogs enjoy the variety, so if your dog is one that handles transitioning to different kibbles well, you could always rotate between a few different formulas/brands if you feel more comfortable knowing she has some variety. Some dogs have no problem with new foods thrown in here and there while others have more delicate stomachs and don't handle it as well, so again, it's an individual thing whether that's a good option in your scenario.