Substitution of Poultry Fat with Black Soldier Fly (Hermetia illucens) Larvae Fat in Dog Diets: Effects on Digestibility, Palatability, Peroxidation of Dry Food, Immunity, Blood Biochemistry, and Faecal Characteristics of Adult Dogs

This study evaluated the effects of partially or fully replacing poultry fat with black soldier fly larvae (BSFL) fat on faecal parameters, blood biochemistry, immune responses, nutrient digestibility, food preference, and lipid oxidation in dogs. A total of 18 adult Golden Retriever dogs (6 dogs per diet group) were subjected to a digestibility trial for 30 days. Three experimental diets were formulated: a control diet (6% poultry fat), BSF3 (3% poultry fat +3% BSF larvae fat), and BSF6 (6% BSF larvae fat). Serum biochemical parameters, including blood urea nitrogen, creatinine, AST, ALT, glucose, cholesterol, triglycerides, total protein, and immunoglobulin levels (IgE and IgG), were analysed from blood samples collected from all dogs. Faecal consistency scores were recorded over 5 days, and faecal pH, ammonia nitrogen (ammonia-N), short-chain fatty acids (SCFAs), and branched-chain fatty acid (BCFA) concentrations were determined during the final three days of the digestibility trial. Seven days after the digestibility trial, a modified two-bowl preference test was conducted over four days using 20 dogs to assess the palatability of the control and BSF6 diets. Lipid oxidation in the diets was evaluated by measuring thiobarbituric acid reactive substances (TBARSs, mg MDA/kg) at baseline (day 0) and after 2, 4, 7, and 10 months of storage at ambient temperature (23-25 °C). BSF6 exhibited the lowest dry matter and organic matter digestibility percentages (<i>p</i> < 0.05). Protein digestibility was reduced in both BSF3 and BSF6, while ether extract digestibility was significantly lower in BSF6 compared to the control diet (<i>p</i> < 0.05). The replacement of poultry fat with BSF larvae fat had no significant effect on serum biochemical parameters or IgE and IgG levels (<i>p</i> > 0.05). Faecal acetic acid concentrations were higher in the control group compared to BSF3 and BSF6, whereas faecal valeric acid concentrations were lower in the control group than in the BSF3 and BSF6 groups (<i>p</i> < 0.05). Although faecal pH and consistency scores were not significantly influenced by the dietary fat source, the total SCFA concentrations in faeces decreased with the substitution of BSF larvae fat (<i>p</i> < 0.05). Furthermore, the dogs demonstrated a higher preference rate for the control diet over the BSF6 diet (<i>p</i> < 0.05). In conclusion, the inclusion of BSF larvae fat in dry dog food formulations reduced nutrient digestibility and palatability but had no adverse effects on the health status of the dogs.