What's actually in Royal Canin Siamese?
We analyzed Royal Canin Siamese Adult Dry Cat Food. The first five ingredients are chicken by-product meal, wheat gluten, corn, wheat, and brewers rice.
This is a weak start. Chicken by-product meal is a rendered product made from chicken parts other than clean meat — think necks, feet, intestines, and undeveloped eggs. It's a concentrated protein source, but it's a clear step below whole chicken, deboned chicken, or even standard chicken meal in terms of ingredient quality. By-product meal as the number one ingredient signals cost optimization, not nutritional optimization.
Wheat gluten at number two is a plant protein concentrate. Its primary function here is to inflate the total protein percentage on the guaranteed analysis — it makes the food look more protein-rich than the animal protein content alone would support. Corn, wheat, and brewers rice round out the top five. That's three grains in the top five ingredients, and none of them are quality whole grains. This formula is grain-heavy in a way that doesn't serve an obligate carnivore. Shop on Amazon →
The good stuff
L-lysine is the standout inclusion and the most breed-relevant ingredient in the formula. Siamese cats are genetically predisposed to feline herpesvirus (FHV-1), which causes upper respiratory infections, eye problems, and chronic flare-ups. L-lysine supplementation is commonly recommended by veterinarians to support immune function and reduce the severity of herpesvirus outbreaks. Finding it in a Siamese-specific food makes sense.
Fish oil provides marine-sourced EPA and DHA omega-3 fatty acids — the forms cats actually need since they're poor converters of plant-based ALA. These support coat health, skin integrity, and inflammation management. For Siamese cats, which are known for their sleek, fine coats, omega-3s are particularly relevant.
L-carnitine helps convert fat into energy, supporting healthy weight management. Siamese cats tend to be lean and active, but L-carnitine is a useful inclusion for any adult cat formula. Dried plain beet pulp is a quality fiber source that supports digestive health and firm stool — far better than powdered cellulose or other cheap fiber fillers.
Taurine is essential for cats — they cannot synthesize it on their own, and deficiency causes serious heart and eye problems. Every cat food should include it, and this one does.
The not-so-good stuff
Chicken by-product meal as the first ingredient is the biggest issue. Royal Canin's other breed-specific cat foods use similar formulas, but "by-product meal first" is a hard sell when competitors like Nulo and Wellness lead with whole, named animal proteins. By-product meal is cheap, concentrated protein — functional but bottom-tier in quality.
Wheat gluten at number two is a plant protein booster. It inflates the protein percentage on the label without delivering the complete amino acid profile that cats need from animal sources. For an obligate carnivore, this is a cost-saving measure disguised as nutrition. The protein number looks good on paper, but the protein quality tells a different story.
Corn at number three adds another low-quality carbohydrate. Corn is a cheap filler with minimal nutritional value for cats. It provides calories but not much else — no meaningful fiber, no essential fatty acids, and poor digestibility compared to quality grains like brown rice or oatmeal.
The double wheat problem compounds things. Wheat gluten at number two and whole wheat at number four means wheat appears twice in the top five. If you combined them, wheat would likely be the single largest ingredient by weight. This is a gluten-heavy formula — a concern for cats with grain sensitivities, and an unnecessary amount of plant-based filler in any cat food.
Corn gluten meal appears further down the list — yet another plant protein concentrate padding the protein numbers. Between wheat gluten and corn gluten meal, this formula relies heavily on plant proteins to hit its targets.
This is the lowest-scoring Royal Canin breed-specific cat food on KibbleIQ. The Siamese formula scores a C/56, which is only 11 points above the generic Royal Canin cat food (D/45). For a product that costs significantly more per pound due to its breed-specific positioning, the ingredient quality doesn't justify the premium.
How it compares
Royal Canin Siamese scores 11 points above the generic Royal Canin cat food (D/45), but that's a low bar. The generic formula earned a D grade. Clearing it by 11 points still leaves the Siamese formula squarely in the average range.
Compared to higher-rated options, the gap is stark. Nulo (B/88) scores 32 points higher with deboned cod, turkey meal, and whole-food carbohydrates. Nulo delivers genuine animal protein quality without the wheat gluten and corn gluten padding. For a Siamese owner looking for the best nutrition, Nulo or a similar B-tier food would be a meaningful upgrade.
Read the full breakdown in our head-to-head comparison: Royal Canin Siamese vs Nulo.
For better alternatives tailored to Siamese HCM, amyloidosis, and dental-periodontal risk, see our full best cat food for Siamese guide.
The bottom line
Royal Canin Siamese Adult Dry Cat Food earns a C grade (56/100) from KibbleIQ. The L-lysine inclusion is genuinely breed-relevant, and fish oil adds functional omega-3s. But chicken by-product meal first, wheat gluten at number two, corn at number three, and double wheat throughout the formula drag the overall quality down. This is a below-average cat food dressed up as breed-specific nutrition. The Siamese-targeted extras don't overcome the base formula's reliance on by-products, plant protein boosters, and cheap grain fillers. Your Siamese deserves better ingredients — and there are plenty of options that deliver them at comparable prices. Shop on Amazon →