Hydrolyzed feather meal in dog nutrition: dry food proximate composition, amino acid content, and biogenic amines

The use of animal by-products from the human food industry to produce commercial pet foods is considered a sustainable practice. This study aimed to characterise the chemical properties of two maintenance diets for adult dogs, achieved by substituting 7% of poultry meal with hydrolyzed feather meal (HFM). Two extruded diets were formulated to be isoenergetic, isonitrogenous, and isolipidic. The control diet (CTR) contained poultry feed), whereas the experimental diet (TRT) included 90 g / kg of poultry meal and 70 g / kg of a commercial HFM product. Both diets contained the same ingredients, nutritional additives, and antioxidants. Triplicate food samples were analyzed for proximate composition, soluble dietary fiber (SDF) and insoluble dietary fiber (IDF) using AOAC (Association of Official Analytical Chemists) methods. Total dietary fiber (TDF) was calculated as the sum of SDF and IDF. Amino acid analysis was performed by gas chromatography, and biogenic amines by high-performance liquid chromatography. Statistical differences between diets were evaluated using a two-sample t-test in R (p ≤ 0.01). The HFM contained approximately (g / 100g, as-fed): 5.59 moisture, 82.64 crude protein (CP), 7.07 crude fat, 0.91 crude fiber (CF), 5.63 starch, 1.83 ash, 2.38 TDF, 0.35 SDF, 2.03 IDF. No significant differences were found between the CTR and TRT diets (g / 100g, as-fed) for moisture (9.16 vs. 8.08), CP (19.07 vs. 19.20), fat (15.24 vs. 15.00), CF (2.10 vs. 2.00), starch (40.59 vs. 40.80), ash (5.45 vs. 5.01), TDF (7.51 vs. 6.97), SDF (1.37 vs. 1.00), IDF (6.14 vs. 5.98), respectively. Additionally, similar values were observed for the amino acid profiles between the two diets. Among the non-essential amino acids, however, serine was present at a significantly higher concentration in the TRT diet compared to the CTR diet (2.20 vs. 2.13 g / 100g, as-fed; p = 0.002). The biogenic amine profile showed no significant differences between the two diets, except for cadaverine, which was significantly higher in the TRT diet compared to the CTR diet (0.124 vs. 0.082 mg / g, as-fed; p = 0.009). Nonetheless, recent studies on the in vitro toxicity of cadaverine to intestinal cells have shown that the cytotoxic levels in food are four times higher than those observed in the diet containing hydrolyzed feather meal. Research supported by the Project ‘BIO = C=O’, PON-MISE I&C 2014–2020 FESR, codex N. F / 200078 / 03 / X45.