Matrix Inconsistency and Calcium–Energy Interactions in Broiler Diets: A Field-Based Mechanistic Analysis of Post-15-Day Diarrhea and Abdominal Fat Deposition

This manuscript presents a field-based mechanistic analysis of a broiler problem reported across several farms in northern Iran: diarrhea beginning around day 15, foamy manure, and abdominal fat deposition. The analysis is based on a field observation conducted at a commercial feed mill in June 2025, combined with mechanistic inference from the published literature. Ten field observations were documented through direct observation of the production line and an unstructured interview with the mill's technical manager. The complete diet formulation was not disclosed due to company confidentiality. The study proposes a three-layer model of matrix inconsistency: (1) a mineral layer involving superdosed phytase, calcium fatty acid powder with inconsistent particle size, limestone, and dicalcium phosphate; (2) an energy layer involving phytase, emulsifier, and multiple fat sources; (3) a filler layer involving bran used as the supplement carrier. A mechanistic chain is proposed in which calcium released explosively in the proventriculus elevates gastric pH, inactivates pepsin, allows undigested protein to reach the ileum and ceca, and creates a substrate for Clostridium perfringens proliferation. A parallel pathway to abdominal fat deposition is proposed through energy-matrix inconsistency and the resulting energy-to-protein (E:P) imbalance. Carbon dioxide — produced only when limestone dissolves — is identified as a separate contributor to foamy manure, gizzard distension, and elevated respiratory rate. The model is presented as a mechanistic hypothesis, not a demonstrated result. Proving it will require in vivo trials with a factorial design. The study also discusses a structural challenge in field research: refusal of a farm visit resulted in the loss of critical clinical data (daily mortality, weekly body weight, water and feed intake, coccidiosis status), and the "single-culprit" habit observed in industry is examined as an obstacle to integrated problem-solving. Keywords: matrix inconsistency; phytase; emulsifier; calcium fatty acid powder; broiler; diarrhea; abdominal fat; field observation; gastric pH; Clostridium perfringens. Related publication by the author: Akbari Shadbad, C. (2025). Conceptual Review of the Potential Synergy of Organic Acidifiers, Calcium Fatty Acid Powder, and Emulsifiers in Poultry Nutrition: A Mechanistic Model and Hypothetical Formulation. Indexed in Civilica. ORCID: 0009-0008-2065-8340.