Plant proteins, such as gluten, soy, and other vegetable-based proteins, are often used as inexpensive fillers and protein sources in dry cat foods. However, these plant-based proteins are considered inferior to animal-based proteins for cats, as obligate carnivores.

Quality and Quantity Factors for Plant Proteins and Soy #

1. Plant Protein Quality Factor: Plant proteins are considered half as valuable as animal proteins for cats. This is represented by a quality factor of 1/2 or 0.5.
2. Gluten and Other Plant Protein Quantity Factor: The quantity factor for gluten and other plant proteins depends on their relative position in the ingredients list compared to the main meat ingredient. The factors range from -9/10 (main protein source) to -1/15 (6th place after meat).
3. Soy Quantity Factor: Similar to gluten, the quantity factor for soy depends on its position relative to the main meat ingredient, ranging from -1/2 (before meat) to -1/20 (6th place after meat).

Calculation of Points Deduction #

The points deducted for plant proteins are calculated based on the total dry matter protein content, the plant protein quality factor, and the respective quantity factor.

1. Gluten or Other Plant Protein:
   Points deducted = (Total dry matter protein %) × (Gluten quantity factor) × (Plant protein quality factor)
   Example: 36% protein, gluten at 2nd place after meat
   Points deducted = 36 × (-1/3) × (1/2) = -6 points
2. Soy:
   If the food contains both gluten and soy, the soy contribution is calculated by removing the gluten portion from the total protein amount.
   Points deducted = [(Total dry matter protein %) × (1 – Gluten quantity factor)] × (Soy quantity factor) × (Plant protein quality factor)
   Example: 40% protein, gluten at 1st place after meat (-1/2), soy at 2nd place after meat (-1/5)
   Points deducted = [40 × (1 – 1/2)] × (-1/5) × (1/2) = -2 points

Examples of How Plant Proteins Affect the Overall Score #

1. A dry cat food with 36% dry matter protein, gluten at the 3rd place after meat (-1/5), and no soy:
   Points deducted = 36 × (-1/5) × (1/2) = -3.6 points
2. A dry cat food with 42% dry matter protein, soy at the 2nd place after meat (-1/5), and no gluten:
   Points deducted = 42 × (-1/5) × (1/2) = -4.2 points
3. A dry cat food with 38% dry matter protein, gluten at the 1st place after meat (-1/2), and soy at the 3rd place after meat (-1/7):
   Points deducted for gluten = 38 × (-1/2) × (1/2) = -9.5 points
   Points deducted for soy = [38 × (1 – 1/2)] × (-1/7) × (1/2) = -1.36 points
   Total points deducted = 9.5 + 1.36 = 10.86 points

The higher the plant protein content and the more prominent its position in the ingredients list, the more points will be deducted from the overall score, reflecting the lower quality of plant proteins compared to animal proteins for cats.