Scientific Guide to Dog Food Selection: Crude Fat and Carbohydrates

Dogs and cats have vastly different nutritional needs. When choosing dog food, you can't just look at crude protein. How much crude fat is appropriate? Is lower carbohydrate always better? Is "grain-free" dog food truly healthier? This article explains it all from a canine nutrition perspective.

I. Characteristics of Canine Nutritional Needs

Omnivorous with a Carnivorous Lean

Dogs can digest carbohydrates better than cats
However, animal protein remains their primary nutritional source
Unlike cats: Dogs can convert tryptophan into vitamin A

Daily Nutritional Ratio Reference

Nutrient	Adult Dog Requirement	Puppy Requirement
Crude Protein	≥18%	≥22%
Crude Fat	≥5%	≥8%
Carbohydrates	30-60%	20-40%
Crude Fiber	1-5%	1-5%
Calcium	0.5-1.0%	1.0-1.8%
Phosphorus	0.4-0.8%	0.8-1.4%

II. Crude Fat — The Overlooked Key Indicator

Functions of Crude Fat

Most concentrated energy source (9 kcal/g vs. 4 kcal/g for protein)
Source of essential fatty acids (linoleic acid, alpha-linolenic acid)
Carrier for fat-soluble vitamins (A, D, E, K)
Key to skin and coat health

Crude Fat Content Selection

Crude Fat	Suitable For	Reason
5-8%	Weight loss/Senior dogs	Calorie control
8-12%	Low-activity indoor dogs	Daily maintenance
12-16%	Active dogs/Working dogs	High energy needs
16-20%	Highly active/Lactating dogs	Very high energy needs
>20%	Professional working dogs	Extreme requirements

⚠️ Pitfall to avoid: Excessively high crude fat + insufficient exercise = obesity. For most household dogs, 8-12% is sufficient.

Fatty Acid Ratio

Omega-6:Omega-3 = 5:1 ~ 10:1
Omega-6 sources: Chicken fat, corn oil
Omega-3 sources: Fish oil, flaxseed
A balanced ratio → glossy coat, anti-inflammatory effects

III. Carbohydrates — The Most Controversial Ingredient

Do Dogs Need Carbs?

Not an essential nutrient (dogs can produce glucose via gluconeogenesis)
However, moderate carbs have practical benefits:
- Provide an economical energy source
- Dietary fiber promotes gut health
- Starch is needed for kibble formation

Calculating Carbohydrate Content

Carbohydrates (NFE) = 100% - Crude Protein% - Crude Fat% - Crude Fiber% - Moisture% - Ash%

Carbohydrate Content Reference

Carb Content	Type	Suitable For
<20%	Low-carb	Active dogs/Weight loss
20-40%	Moderate-carb	Most dogs
40-60%	High-carb	Low-end food (cost-driven)

"Grain-Free" ≠ Low-Carb

Grain-free foods use potatoes/peas/chickpeas to replace corn/wheat
Carb content can be the same or even higher
Grain-free ≠ healthier; grain allergies are rare in dogs

FDA Warning

In 2018, the FDA investigated a potential link between grain-free diets and canine dilated cardiomyopathy (DCM)
Possible cause: Legumes/peas may affect taurine absorption
The conclusion is not final, but caution is warranted

IV. Deep Dive into the Ingredient List

Characteristics of a Good Dog Food Ingredient List

The first two ingredients are clearly named meats (chicken/beef/fish)
Fat sources are clearly stated (chicken fat/fish oil, not "animal fat")
No vague ingredients ("meat by-products" / "animal fat")
Contains moderate fiber (beet pulp/chicory root)

Red Flags for Bad Dog Food

First ingredient is corn/wheat/soy
Contains "meat by-products" (opaque source)
Artificial colors (Red 40, Yellow 5, Blue 2, etc.)
Preservatives like BHA, BHT, Ethoxyquin
Added sugar/syrup

Converting Meat Content

Fresh meat is about 70% water; after drying, it accounts for only 30%
"Chicken" listed first ≠ chicken is the highest in dry matter
Dehydrated chicken/chicken meal is protein-concentrated, meaning actual meat content is higher

V. Choosing Food by Dog Size

Small Breeds (<10 kg)

Higher metabolic rate → need higher caloric density
Smaller kibble size → easier to chew
Watch for dental tartar → consider dental health formulas

Medium Breeds (10-25 kg)

A balanced, all-purpose formula works well
Joint health support (chondroitin/glucosamine) can be considered

Large Breeds (25-45 kg)

Control growth rate (avoid overfeeding during puppyhood)
Calcium-to-phosphorus ratio of 1.2:1 ~ 1.4:1
Joint health support is a must
Larger kibble to slow down eating

Giant Breeds (>45 kg)

Low calcium and low calories during puppyhood (to prevent rapid bone growth)
Focus on heart and joint health in adulthood
Soak kibble to slow eating → prevent gastric dilatation-volvulus (GDV)

VI. Transitioning and Feeding Dog Food

Principles of Food Transition

Gradual transition over 7-10 days
Monitor stool quality (Bristol Stool Scale score 2-3)
Frequent food changes are not recommended

Feeding Amount

Start with the recommended amount on the package
Adjust based on body condition:
- Ribs easily felt but not visible = ideal weight
- Ribs not felt = overweight → reduce by 10%
- Ribs protruding = underweight → increase by 10%

Feeding Frequency

Puppies (<6 months): 3-4 times/day
Young dogs (6-12 months): 2 times/day
Adult dogs: 1-2 times/day
Large breeds must be fed in 2 portions → prevent GDV

VII. Pitfalls to Avoid When Buying

❌ Only looking at crude protein → Crude fat and carbs are equally important
❌ Blindly trusting "grain-free" → Grain allergies are rare; grain-free ≠ better
❌ Colorful food → Artificial colors are meaningless for dogs
❌ Thinking bigger kibble is more economical → Choose kibble size based on dog size
❌ Feeding puppy food to adult dogs → Nutritional needs differ greatly
❌ Continuing high-fat food for overweight dogs → Obesity is the #1 health issue for household dogs

💡 Summary: The core of dog food selection comes down to three things — crude protein (≥22% high-quality animal protein), crude fat (8-12% moderate), and carbohydrates (lower is better, but no need to pursue extremely low levels). "Grain-free" is not a guarantee of health; a clear meat source is far more important. Choose food based on your dog's size: large breeds need joint support, small breeds need dental care.