Skip to content
In The Kibble
My dogs

Ingredient file // Fat or oil

Fish Oil

Useful omega-3s, but the dose stays hidden

Fish oil is fat separated from whole fish or fish processing trimmings. It supplies EPA and DHA, which dogs absorb and which have shown modest benefits in some joint trials. The ingredient name reveals neither the fish species nor the EPA and DHA dose.

Role in the food Supporting nutrient
Fish Oil
What it is
Oil separated from fish tissue, supplying dietary fat and varying amounts of the omega-3s EPA and DHA.
Made from
Whole fish or fish processing trimmings
Main job
EPA and DHA source
Typical amount
Not published
Watch for
Oil that oxidizes during storage
Not the same as
Fish meal

Our read // In our catalog

In 1 of every 5 foods we track

Share of foods that list it

21%

652 of the 3,105 foods with an ingredient list on file, from 43 brands. 447 dry dog food, 157 wet dog food, 20 frozen dog food.

Each square is 1% of the catalog

Where it sits on the label

Median position 13. In the top five of 6 foods, so it is usually a minor ingredient.

Top five List position, heaviest first

Above the salt

71%

Listed before the salt in 71% of foods. In the rest it is under about 1% of the recipe.

Price per lb

Foods with it $3.32
All foods $3.25

Median of the cheapest bag price across 399 priced foods, about level with the catalog. The price is the food's, not the ingredient's.

Who leans on it

23%

of the foods that list it are from Royal Canin. 43 brands use it in total.

The story

From lamp fuel to a puppy food omega-3 minimum

Much of the US fish oil story runs through the Atlantic menhaden, a small, oily, herring-like fish of the East Coast. Native Americans used it to fertilize crops, and European settlers rendered it into fuel for lamps. Better processing in the mid-19th century expanded the industry, sending the oil into paints and the solids into fertilizer. A reduction plant on Cockrell Creek in Reedville, Virginia, has run continuously since 1878.14,15

Feed came next. After vitamin B12 was found in menhaden, its protein moved into animal feeds, and the industry grew again after World War II. Today Virginia is the last place on the East Coast where menhaden is cooked to extract oil. The omega-3 rich oil goes into supplement pills, and the cooked, pressed remains become pet food or fertilizer.14,15

Researchers later tested the fats in dogs. In a 1998 trial, dogs with surgically reduced kidney mass kept better kidney function on menhaden oil than on safflower oil. In 2005, a separate team reported that puppies fed preformed DHA through pregnancy, nursing and weaning built more plasma DHA and had stronger retinal responses than puppies fed plant omega-3.18,19

Today AAFCO recommends at least 0.05% EPA plus DHA on a dry matter basis in foods for growth and reproduction, and sets no minimum for adult maintenance. The National Research Council puts the safe upper limit for dogs at 280 mg of EPA plus DHA per 100 kcal. Concentrated supplements are treated as therapeutic. That wide gap between a puppy recommendation and a treatment dose is why the words fish oil on a label say so little.16

What it is

How it is made

Fishmeal plants process whole fish and trimmings left by seafood processors. Cooking releases oil from the tissue. The plant separates that oil from water and solids, then turns the solids into fish meal.7,8,9

  1. 01 // Source Fish and trimmings Whole fish or cuttings from seafood processing arrive at a plant that makes fish meal and oil.
  2. 02 // Process Cooked and pressed Heat releases oil from fish tissue, and pressing squeezes liquid away from the cooked solids.
  3. 03 // Process Oil separated Centrifuges separate the oil from water and fine solids in the pressed liquid.
  4. 04 // Output Fish oil The separated oil goes to feed makers as a fat ingredient that needs protection from oxidation.

What is in it

Composition, dry matter

10-30

% EPA+DHA

The approximate share of these fats in unmodified fish oils. The ingredient name alone cannot tell you how much reaches the bowl.

EPA 6.3-13%6
DHA 4.2-18.2%6
Total fat 100%5
Protein 0%5

The EPA and DHA ranges compare herring and salmon oils, not every fish oil. Species and concentration steps change the amounts. USDA reports no water in its sardine oil entry, making its fat and protein figures dry matter figures.5,6

Benefits

What it does for your dog

Each benefit carries the same evidence grade as the claims below.

  1. 01

    Better retinal development in puppies

    Fish oil supplies preformed DHA. In one trial, puppies fed marine DHA built more blood DHA than puppies fed plant omega-3, and at 12 weeks the high marine group had stronger retinal responses.19

    1. Strong
    2. Some
    3. Thin
    4. None
  2. 02

    Easier movement in arthritic dogs

    In a 90-day trial, a joint food high in fish oil omega-3s improved weight bearing in arthritic dogs. That food stated a high dose; an ordinary food listing fish oil promises nothing comparable.17

    1. Strong
    2. Some
    3. Thin
    4. None

Why it is in the bag

A real omega-3 source, in unstated amounts

  1. Main nutrition
  2. Supporting nutrient
  3. Does a job
  4. Mostly filler

Makers add fish oil for EPA and DHA, omega-3s that dogs absorb and that AAFCO recommends in puppy foods. It often sits partway down the list, so it is present in smaller amounts than the ingredients listed above it. That position cannot tell you whether the amount is small or a joint diet dose of 160 to 340 mg per 100 kcal. Blood levels track the amount fed; only an EPA and DHA guarantee states it.1,12,16

  1. 01

    Supplies EPA and DHA

    Dogs absorb these fats. In a controlled feeding trial, blood EPA and DHA rose as their concentrations increased in the food.1

  2. 02

    Adds dietary fat

    Fish oil contributes energy without protein or fiber. Fish meal supplies protein, so the two ingredients do different jobs.5,9

  3. 03

    Uses the processing stream

    The same cooked fish yields oil and meal. Recovering oil gives fish processors another saleable product when the raw material contains enough fat.7,8

How much One trial tested complete foods containing 0.8 to 2.9% EPA plus DHA on a dry matter basis, not a usual fish oil amount.1

Our read // The claims

What the evidence supports

Strong: controlled studies in dogs agree. Some: small or mixed dog data. Thin: mechanism or lab work only. None: nothing, or the evidence points the other way.

  1. Brands say

    Fish oil raises a dog's EPA and DHA

    Evidence

    1. Strong
    2. Some
    3. Thin
    4. None

    In a randomized trial of 177 dogs, blood EPA and DHA rose with their concentrations in the food. A separate fish oil trial also measured rising blood levels. The ingredient list still gives no dose.1,2,12

  2. Vets say

    Fish oil eases arthritic joints

    Evidence

    1. Strong
    2. Some
    3. Thin
    4. None

    A 177-dog trial found modest improvements at its highest EPA and DHA level. An independent 77-dog trial found no significant difference from corn oil on its main outcomes. A routine fish oil listing does not promise a treatment dose.1,2

  3. Brands say

    DHA from fish oil makes puppies smarter

    Outruns the evidence

    Evidence

    1. Strong
    2. Some
    3. Thin
    4. None

    A 12-puppy trial found better results on one learning task after a measured DHA-rich supplement. That small result does not show that any puppy food listing fish oil improves learning.4

  4. Brands say

    Fish oil cures itchy skin

    Outruns the evidence

    Evidence

    1. Strong
    2. Some
    3. Thin
    4. None

    A 16-dog trial found less itching with a measured marine oil supplement than with corn oil. Another diet trial combined EPA with GLA. Neither tested a cure, and neither shows an effect from the undisclosed amount in ordinary food.3,13

  5. Owners say

    Fish oil on the label means mercury exposure

    Outruns the evidence

    Evidence

    1. Strong
    2. Some
    3. Thin
    4. None

    A study of pet food ingredients found no mercury above its detection limit in the fish oil samples tested. That does not certify every supplier, but the ingredient name alone is not evidence of exposure.11

The research

Studies worth knowing

Published research we read for this page, dog studies first.

  1. 2010 // Feeding trial, 2 foods

    Arthritic dogs bore more weight on a fish oil food17

    38 client-owned dogs with osteoarthritis at 2 university clinics

    Found. Dogs ate a regular commercial food or a test food with 3.5% fish oil omega-3s. Over 90 days, force plates showed better weight bearing in 82% of test food dogs versus 38% of control dogs.

    What it means. A joint food with a stated high omega-3 level helped within 3 months. A plain fish oil listing does not tell you the dose.

  2. 1998 // Feeding trial, 3 fats

    Menhaden oil slowed kidney decline in dogs18

    21 dogs with surgically reduced kidney mass

    Found. Groups of 7 dogs ate a diet with 15% added fat from fish oil, safflower oil or beef tallow for 20 months. Kidney filtration averaged 1.43 ml/min/kg on fish oil versus 0.89 on safflower oil.

    What it means. This was a lab model at a very high fish oil dose. It explains why kidney diets add fish oil, not what a regular food does.

  3. 2005 // Feeding trial, 3 diets

    Puppies fed marine DHA had stronger retinal responses19

    Puppies whose mothers ate the test diets through pregnancy and nursing

    Found. Puppies fed preformed DHA built more blood DHA than puppies fed plant omega-3. At 12 weeks, the high marine group had the best retinal tests and the low omega-3 group the poorest.

    What it means. Plant omega-3 is a weak stand-in for fish DHA in puppies, so the fat source in a puppy food matters.

Straight answers

What owners ask

  1. Q01

    Is it just filler?

    No

    It adds fat and supplies EPA and DHA. Dogs fed measured amounts showed increases in those fats in their blood. Its place on the ingredient list cannot tell you how much it supplies.1,5,12

  2. Q02

    Can I tell which fish?

    Not here

    The name fish oil does not identify a species. Published herring and salmon oil figures differ substantially. A named source tells you more about origin; an EPA and DHA guarantee tells you more about the dose.6,12

  3. Q03

    Does it mean mercury?

    No

    Fish oil samples in one pet food ingredient study had no mercury above the test's detection limit. The result applies to those samples, not every supplier. A fish oil listing is not a mercury measurement.11

Who uses it

Brands, best sellers and the company it keeps

Top brands, by foods that list it

  1. Royal Canin 150
  2. Blue 85
  3. Purina 67
  4. Hill's 51
  5. Eukanuba 24
  6. Authority 21
  7. Acana 20
  8. Merrick 20
  9. Iams 14
  10. The Honest Kitchen 14

Plus 33 more brands.

Amazon best sellers that list it

  1. #9 Purina Pro Plan Adult Sensitive Skin & Stomach Salmon & Rice Formula Dry Dog Food
  2. #20 Purina Pro Plan Adult Small Breed Shredded Blend Chicken & Rice Formula Dry Dog Food
  3. #23 Purina Pro Plan Adult Sensitive Skin & Stomach Small Breed Formula Dry Dog Food
  4. #26 Purina Pro Plan Puppy Chicken & Rice Formula Dry Dog Food
  5. #27 Blue Life Protection Formula Senior Chicken and Brown Rice Recipe Dry Dog Food
  6. #29 Royal Canin Small Adult Dry Dog Food
  7. #30 Blue Life Protection Formula Puppy Chicken and Brown Rice Recipe Dry Dog Food
  8. #33 Purina One SmartBlend Sensitive Systems Formula Adult Premium Dry Dog Food

Rank on Amazon's dog food best seller list, checked October 2026.

Usually listed with, share of the foods that list it

  1. Natural Flavor 47%
  2. Chicken 46%
  3. Chicken Fat 43%
  4. Brewers Rice 30%
  5. Brown Rice 27%
  6. Dried Plain Beet Pulp 27%
  7. Chicken Meal 22%
  8. Chicken By-Product Meal 22%
  9. Flaxseed 20%
  10. Wheat Gluten 19%
  11. Corn 19%
  12. Peas 18%

On the shelf

Foods that list it

652 foods in our reviews list it. Here are some of them.

Authority Sensitive Stomach & Skin Shreds in Broth Adult Dog Meal Dog Food Topper90.0% proteinBlue True Solutions Mobility Support Wet Dog Food31.8% proteinVital Essentials Duck Soft Nibs Freeze-Dried Dog Food48.9% proteinVital Essentials Entrée (Nibs) Chicken Nibs Freeze-Dried Dog Food54.3% proteinVital Essentials Raw Entrées Duck Entree Patties Frozen Dog Food55.6% proteinWeruva Dogs in the Kitchen Puppy Chicken Formula in Gravy Wet Dog Food60.0% protein
Show 57 more ZIWI Steam & Dried Lamb with Green Vegetables Recipe Dog Food Topper38.6% proteinZIWI Steam & Dried Beef with Pumpkin Recipe Dog Food Topper38.6% proteinZIWI Steam & Dried Cage-free Chicken with Orchard Fruits Recipe Dog Food Topper40.9% proteinPrimal Freeze-Dried Raw Scoopable Pronto Dog Food Topper42.4% proteinPurina Dog Chow High Protein Real Beef Dry Dog Food30.0% proteinPurina Pro Plan Senior Small Breed Shredded Blend Chicken Rice Dry Dog Food34.1% proteinPure Balance Pro+ Large Breed Chicken & Brown Rice Recipe Dry Dog Food24.4% proteinPure Balance Pro+ Weight Management Chicken & Oatmeal Recipe Dry Dog Food27.2% proteinPurina Dog Chow High Protein Real Chicken Dry Dog Food30.0% proteinPurina Pro Plan Development Puppy Small Breed Chicken Rice Dry Dog Food37.5% proteinPure Balance Pro+ Senior Salmon & Brown Rice Recipe Dry Dog Food26.7% proteinHill’s Prescription Diet ONC Care Chicken & Vegetable Stew Wet Dog Food30.0% proteinWeruva Awesome Functions Awesome Bouncy Beef & Riceberry For Joint Health Wet Dog Food35.3% proteinWeruva Awesome Functions Awesome Bouncy Chicken Breast & Riceberry Recipe with Veggies, Turmeric & Ginger Wet Dog Food42.1% proteinWeruva Awesome Functions Awesome Shiny Chicken Breast & Brown Rice Recipe with Veggies & Flaxseed Wet Dog Food38.1% proteinWeruva Awesome Functions Awesome Shiny Beef & Brown Rice Recipe with Flaxseed Wet Dog Food35.3% proteinViva Raw Pure Puppy Recipe Frozen Dog Food57.3% proteinWeruva Awesome Functions Awesome Bouncy Chicken & Riceberry For Joint Health Wet Dog Food42.1% proteinWeruva Awesome Functions Awesome Shiny Chicken & Rice For Skin & Coat Health Wet Dog Food42.1% proteinWeruva Dogs in the Kitchen Dog Steak Frites Dinner Beef & Pumpkin Dry Grain-Free Freeze-Dried Dog Food38.0% proteinHill’s Prescription Diet d/d Salmon Skin Care Wet Dog Food15.9% proteinHill’s Prescription Diet i/d Puppy Turkey Digestive Care Wet Dog Food27.3% proteinHill’s Science Diet Puppy Savory Stew with Chicken & Vegetables Wet Dog Food30.6% proteinBones & Co Cage-Free Chicken Raw - The Bones & Co. Freeze-Dried Dog Food36.6% proteinRoyal Canin Comfort Care Loaf in Sauce Wet Dog Food38.9% proteinBones & Co Cage-Free Turkey Raw - The Bones & Co. Freeze-Dried Dog Food37.6% proteinPrimal Raw Nuggets - Turkey & Sardine Recipe Frozen Dog Food56.5% proteinBones & Co Grass-Fed Beef Raw - The Bones & Co. Frozen Dog Food43.8% proteinBones & Co Cage-Free Turkey Raw - The Bones & Co. Frozen Dog Food41.9% proteinBones & Co Grass-Fed Lamb Raw - The Bones & Co. Frozen Dog Food40.6% proteinBones & Co Cage-Free Chicken Raw - The Bones & Co. Frozen Dog Food41.9% proteinBones & Co Cage-Free Duck Raw - The Bones & Co. Frozen Dog Food45.3% proteinBones & Co Grass-Fed Beef Raw - The Bones & Co. Freeze-Dried Dog Food38.7% proteinVital Essentials Soft Nibs Beef Freeze-Dried Dog Food43.5% proteinPrimal Raw Scoopable Pronto Puppy Frozen Dog Food48.0% proteinPrimal Raw Scoopable Pronto Puppy Freeze-Dried Dog Food41.3% proteinPrimal Raw Patties - Turkey & Sardine Recipe Frozen Dog Food56.5% proteinPrimal Canine Raw Nuggets - Venison Frozen Dog Food55.6% proteinWeruva Dogs in the Kitchen Awesome Everything Beef, Rice & Veggies Multicare Wet Dog Food37.5% proteinPrimal Freeze-Dried Raw Nuggets Dog Food Topper44.6% proteinEdgard & Cooper Farm-Raised Lamb Adult Dog Grain-Free Dry Dog Food25.6% proteinEdgard & Cooper Chicken & Salmon Dog Grain-Free Dry Dog Food24.4% proteinJinx : Grass-Fed Lamb for Everyday Nutrition Dry Dog Food29.5% proteinEdgard & Cooper Free-Run Duck with Venison Adult Dog Grain-Free Dry Dog Food26.7% proteinEdgard & Cooper Free-Run Chicken & Duck Puppy Dry Dog Food28.9% proteinJinx Grass-Fed Beef, Brown Rice, and Sweet Potato Dry Dog Food30.0% proteinEdgard & Cooper Atlantic Salmon Adult Dog Dry Dog Food26.7% proteinEdgard & Cooper Free-Run Chicken Adult Dog Dry Dog Food27.8% proteinHill’s Adult Healthy Cuisine Roasted Chicken, Carrots & Spinach Stew Wet Dog Food26.7% proteinJinx Chicken & Vegetable Bone Broth Stew Wet Dog Food44.4% proteinDave’s Pet Food Dave’s Stewlicious Shepherd’s Pie with Lamb & Beef For Dogs / 13.2 oz Wet Dog Food44.4% proteinDave’s Pet Food Dave’s Stewlicious Chunky Cowboy Dinner with Beef and Pork for Dogs / Wet Dog Food44.4% proteinDave’s Pet Food Dave’s Stewlicious Chicken Pot Pie Dinner for Dogs / Grain-Free Wet Dog Food40.9% proteinEdgard & Cooper Tins Chicken & Turkey Adult Dog Grain-Free Wet Dog Food44.4% proteinJinx Beef Bone Broth Stew Wet Dog Food44.4% proteinAuthority Sensitive Stomach & Skin Chicken Entree Adult Dog Wet Dog Food22.7% proteinAuthority Everyday Health Chicken & Vegetable Entree Senior 7+ Wet Dog Food36.4% protein

Our read // On the bag

Look for an EPA and DHA amount

Fish oil low on the list is a purposeful fat addition, but its position gives no usable EPA or DHA dose. Read the ingredients above it to judge the main recipe. If omega-3 content matters to you, look for an EPA and DHA guarantee or ask the maker for the amounts.

Sources

What we read

Checked September 1, 2026.

  1. 1 Dose-Titration Effects of Fish Oil in Osteoarthritic Dogs Journal of Veterinary Internal Medicine, 2010 // Journal
  2. 2 An un-commissioned randomized, placebo-controlled double-blind study to test the effect of deep sea fish oil as a pain reliever for dogs suffering from canine OA BMC Veterinary Research, 2012 // Journal
  3. 3 Double-blinded Crossover Study with Marine Oil Supplementation Containing High-dose icosapentaenoic Acid for the Treatment of Canine Pruritic Skin Disease Veterinary Dermatology, 1994 // Journal
  4. 4 The Supplementation of Docosahexaenoic Acid-Concentrated Fish Oil Enhances Cognitive Function in Puppies Animals, 2023 // Journal
  5. 5 USDA National Nutrient Database for Standard Reference, Release 28: Fats and Oils U.S. Department of Agriculture, 2015 // Government
  6. 6 Seafood Choices: Balancing Benefits and Risks National Academies Press, 2007 // Book
  7. 7 The production of fish meal and oil - 3. The process Food and Agriculture Organization of the United Nations, 1986 // Government
  8. 8 Marine Oils American Oil Chemists' Society, n.d. // Industry
  9. 9 Fish oil Feedipedia, n.d. // Database
  10. 10 Potential Adverse Effects of Omega-3 Fatty Acids in Dogs and Cats Journal of Veterinary Internal Medicine, 2013 // Journal
  11. 11 Toxic element levels in ingredients and commercial pet foods Scientific Reports, 2021 // Journal
  12. 12 Reading Labels AAFCO, n.d. // Regulator
  13. 13 A randomized, double-blinded, placebo-controlled multicenter study on the efficacy of a diet with high levels of eicosapentaenoic acid and gamma-linolenic acid in the control of canine atopic dermatitis Veterinary Dermatology, 2004 // Journal
  14. 14 Menhaden Fishing Industry (Historical Marker SC-214) Delaware Public Archives, n.d. // Reference
  15. 15 Menhaden in Virginia Virginia Places, n.d. // Reference
  16. 16 Fish Oil Dosing in Pet Diets and Supplements Today's Veterinary Practice, 2020 // Journal
  17. 17 Evaluation of the effects of dietary supplementation with fish oil omega-3 fatty acids on weight bearing in dogs with osteoarthritis Journal of the American Veterinary Medical Association, 2010 // Journal
  18. 18 Beneficial effects of chronic administration of dietary omega-3 polyunsaturated fatty acids in dogs with renal insufficiency Journal of Laboratory and Clinical Medicine, 1998 // Journal
  19. 19 Long-chain (n-3) polyunsaturated fatty acids are more efficient than alpha-linolenic acid in improving electroretinogram responses of puppies exposed during gestation, lactation, and weaning The Journal of Nutrition, 2005 // Journal
An ingredient on its own tells you very little. What matters is how much of it there is and where it sits in the list. That is why we weigh the top five rather than reacting to any single name further down. Back to the wiki

Keep In The Know,
Know What's In The Bowl

The In the Kibble newsletter. Useful emails for dog owners: what we find inside dog food, how to feed well, and a heads-up when a food is recalled.
DOUBLE OPT-IN // ONE CLICK TO STOP // NEVER SHARED