PSVIII-11 - Antinutritional factors are largely mitigated by extrusion and did not negatively impact digestibility of canine grain-free and grain-inclusive foods

Abstract: Ingredients commonly used in companion animal foods, such as whole grains and legumes, naturally contain antinutritional factors (ANF). Some ANF are known contributors to reduced nutrient digestibility and bioavailability, potentially resulting in defective protein synthesis, which is one hypothesis of potential root cause(s) for dilated cardiomyopathy. Yet some ANF, such as trypsin inhibitor (TI) and isoflavones, may act as beneficial bioactives at lower inclusion levels. While various processing methods can impact the presence or activity of ANF, the purpose of this investigation was to assess the presence of ANF in ingredients commonly used in canine foods, the effect of extrusion on ANF, and the subsequent digestibility of foods formulated using different ingredient strategies. Four test foods were formulated to meet requirements for adult dogs at maintenance: (1) grain-inclusive without peas or potatoes, (2) grain-inclusive with peas and pea fiber, (3) grain-free with peas and potatoes, and (4) grain-free with potatoes (Table 1). Grains, legumes, plant proteins, and finished test foods were analyzed for 41 ANF. Percent destruction of ANF was calculated from the inclusion levels of ingredients in the formulations and the tested levels in finished foods. Digestibility studies were then conducted to assess macronutrient digestibility of the test foods. Cereal grains and soybean meal were the primary sources of ANF in raw ingredients. Phytic acid, TI, and isoflavones (daidzin & genistin) were the most common ANF measured in ingredients. Lectin was not detectable in any ingredients or test foods; tannins were detected only in soybean meal. Except for phytic acid and TI, ANF were effectively ( >99%) destroyed by this extrusion process. Trypsin inhibitor was detectable at levels slightly above the detection limit (1000 TIU/g) in all finished test foods (Table 2; 1200-1700 TIU/g). Phytic acid was detectable (0.49-0.76%) in all finished test foods except for the grain-free with potatoes formulation. This was unsurprising as both are known to be resistant to inactivation by heat, pressure and steam. Despite their presence in finished test foods, apparent DM, carbohydrate (NFE), and energy digestibility were high ( >80%) for all foods; apparent fat and true protein digestibility were >90% (Figure 1). These data demonstrate the effectiveness of this specific extrusion process to minimize or mitigate the majority of ANF in canine foods when formulated with a variety of common ingredients. Despite the presence of these ANF, test foods remained highly digestible, demonstrating the importance and effectiveness of balanced nutritional formulation in mitigating their effects. We assert that the presence or absence of ANF in ingredients should not, by itself, be the reason for use or avoidance of an ingredient. Additional factors such as the quality of the raw ingredient, processing methods, and overall nutritional design must be considered.