PS7-7. Interlaboratory Variability in Total Dietary Fiber Measurements in Fresh Refrigerated Dog Foods.

Abstract Total dietary fiber (TDF) is now a required nutrient listing under the Pet Food Label Modernization Act published in the American Feed Control Officials’ 2024 Official Publication. TDF analysis is complex and can produce variable results depending on method modifications and food matrices. These challenges may be particularly pronounced in fresh meat-based pet foods, which differ substantially from the cereal-based matrices for which many TDF methods were originally developed. These pet food products are typically characterized by high moisture, high protein, and relatively low intrinsic fiber concentrations, conditions that may or may not contribute to analytical variability. The objective of this study was to evaluate interlaboratory variability in TDF measurements in fresh refrigerated dog foods. A total of 7 roasted meals and 6 rolls were analyzed in triplicate by three ISO-17025 accredited commercial laboratories (A, B, and C), all using AOAC Method 991.43 with some laboratory-specific procedural modifications. All laboratories defatted the samples before fiber analysis, and TDF was calculated as the sum of insoluble dietary fiber and soluble dietary fiber. Triplicate results were averaged prior to statistical analyses performed using R (v. 4.5.2). Due to intrinsic formulation differences, roasted meals and rolls data were analyzed separately. A p-value < 0.05 was considered statistically significant, while p-values between 0.05 and 0.1 were considered trends. Despite the use of a comparable analytical method, significant differences were observed among laboratories in reported TDF values. For roasted meals, Lab A reported lower average TDF than Lab B (3.06% vs. 4.40%, as-is) and showed a tendency toward lower values than Lab C (3.06% vs. 3.92%, as-is). There were no statistical differences between Labs B and C for roasted meals. For rolls, TDF values differed significantly between Labs B and C (3.18% vs. 2.12%, as-is, respectively), while no significant differences were observed between Lab A and the other labs. Notably, the laboratory reporting the lowest TDF values differed between roasted meals and rolls; Lab A reported the lowest TDF values for roasted meals, whereas Lab C reported the lowest values for rolls. These results demonstrate that substantial interlaboratory variability may occur when measuring TDF in fresh pet foods, even when a comparable validated method is used. The findings highlight the analytical challenges associated with meat-based matrices and suggest the need for improved standardization and metric specific analytical considerations to ensure reliable fiber quantification.