, Coconut oil has no EFAs. If you want to, say, add EPA/DHA to the diet, you won't get any of that from CO. Fish oil has a different kind of lipid than CO, so they are not interchangeable.
CO may potentially have some other benefits though, so you might reasonably choose to give both. (However, CO's benefits are somewhat speculative as there's no peer-reviewed literature confirming any of the CO benefits in dogs at this point in time
-- just lots of extrapolation from in vitro studies). The Internet Commentariat makes it sound like it's a cure-all and proven winner...and the science just isn't there to support that, at least not yet -- but there are some promising in vitro studies, and it's generally harmless, so it's reasonable to see if you get a benefit, particularly where there are lots of anecdotal reports of it helping.
2. Fish oil is something I've been doing a fair amount of reading lately, as it's a complicated product. It can easily be rancid, contain other oil than that on the label, or contain mercury or other contaminants. We have to all ask ourselves why we are assuming any particular brand is good quality. The marketing? The price? The pretty label? The website?
In the USA, it's not FDA regulated--whether for pets OR people. No government agency is testing it. If it's not third-party certified, this industry is so ugly that there is really no reason to assume you are even getting the type of fish specified on the label -- or even any EFAs. Ask whether it's third-party certified -- and then dig into what that certification means.
Consumer Lab tests it (but it's behind a paywall). A new startup called Lab Door also started testing various human brands: https://labdoor.com/rankings/fish-oil
IMHO human-grade is better ONLY because you can get it easily with a reliable third-party certification of quality. For example, USP certification is an easy-to-find indication of a manufacturer investing in testing for purity and plant audits-- Dietary Supplements Verification
. Some retailers hold their vendors to high quality standards for human-grade supplements -- Whole Foods, for example. By contrast, the pet supplement industry is kind of terrifying to me -- who knows what's even in the bottle. I would LOVE to see pet supplement manufacturers doing third-party certifications.
3. You can easily find doses of human-grade Vitamin E that are (probably) safe for big dogs. 100, 200, and 400 IU doseages are widely available. Most sources that I've seen say a 400 IU a few times a week
is plenty -- if you find a scientific source that says you need that much daily, please post it, as I haven't seen it.
I prefer mixed tocopherols (which you cannot get at CVS or WM, but you can get at Whole Foods, or a health store, or online.) You can find some doseage guidelines for canines here: Fat Soluble Vitamins: Vitamin A, D, E, & K in Dogs
I would err on the low side of the doseage here, not the high side, as there are a lot of unknowns with Vitamin E in dogs currently. There's research coming out
in humans that high E supplementation (400 IU) actually shortens life span, and there's a lot of confusion as to why. Be cautious until the biologocial mechanism in supplementation is better understood, as it may shed some light on dogs too. That study caused me to be a lot more cautious about E supplementation in dogs (and me). Feeding vitamin E rich foods might be the better option -- the uncertainty right now is concerning to me.
4. A lot gets posted online about salmon being better than other fish (esp. "unidentified" fish), but the "unidentified" is actually often identified on the fine print as anchovies or sardines (see, for example, the Costco Fish Oil label -- it's clear that it's from anchovies and sardines on the back of the bottle). All 3 kinds of fish have DHA and EPA in varying levels -- it's the DHA/EPA content that you're really buying, and whether it's bioavailable, contaminant-free, and safely processed. When you are sourcing EFAs, you aren't buying meat for the grill -- and I sometimes wonder if that's what the "salmon is better" claims from manufacturers are playing off of (unappetizing little fish may not be welcome on your dinner plate, but may be a perfectly good source of EFAs).
My worry is that the higher up the food chain, the more likely you are to pick up dioxin, PCBs and other nasty contaminants, so it may be safer lower on the marine food chain, if you want to avoid more contaminants. Salmon in supplements is also very likely farmed unless you are buying fairly expensive supplements. Farmed fish seems to be pretty dirty. I also feel better about the sustainability of harvesting little, rapidly producing fish for this use.
So...fish oil is complicated...very complicated. My thinking on it is still developing, as I continue to read.