Fish Feed • 7 min read • September 05, 2026

The True Cost of Substandard Protein: Identifying Soya-Meal Overuse and Bone Ash Adulteration

D
Dr. Emmanuel Adeleke
Feed Formulation & Nutrition
The True Cost of Substandard Protein: Identifying Soya-Meal Overuse and Bone Ash Adulteration
Crude protein percentages on feed labels can be deceptive. Learn how laboratory proximate analysis exposes poorly toasted soybean meal and insoluble ash fillers.

The Protein Quality Deception

A laboratory Dumas test measures Total Nitrogen to calculate Crude Protein ($$CP = N \times 6.25$$). Unscrupulous feed compounders exploit this by adding high-nitrogen non-protein fillers or excessively unrefined poultry feather meal that fish digestive enzymes cannot break down.

1. The Anti-Nutritional Factors in Raw Soy

Raw or under-toasted soybean meal contains trypsin inhibitors that block protein breakdown in catfish stomachs. Feeding this induces severe gut inflammation, stunted growth, and loose watery feces that foul the water.

2. Excess Ash and Bone Scrapings

Quality feeds maintain ash levels below 9%. When ash exceeds 13%, it indicates excessive bone scrapings and sand fillers, displacing vital digestible energy and causing sluggish feeding behavior.

Direct Farm Consultation

HAVE A FISH FARMING QUESTION?

Our technical biologists and pond managers assist farmers with water quality analysis and stocking setups.

Related Insights

All Articles →