The impact of full-fat Hermetia illucens larvae meal on the health and immune system function of broiler chickens.

Introduction: Alternative protein sources have recently been attracting growing interest as potential components of livestock nutrition. This study evaluated the effect on broiler health of replacing the soybean protein component of poultry feed with processed insect protein from farmed Hermetia illucens (HI) larvae.

Material and methods: A total of 384 male broiler chicks were divided into four diet groups (eight pens/treatment and 12 birds/pen) and reared to the 42^nd day of life (dol). Each treatment group received a starter diet until the 14^th dol, then a grower diet until the 35^th and finally a finisher diet until the 42^nd. The soybean meal in standard diets was replaced with full-fat HI larvae meal in the following amounts: 0% for the control group HI-0, 50% for group HI-50, 75% for group HI-75, and 100% for group HI-100. At 1 dol, chicks were vaccinated against Marek's disease, coccidiosis, Newcastle disease and infectious bronchitis and at 7 dol against avian metapneumovirus infections using live-attenuated vaccines. Blood and spleen samples were collected at three and six weeks of age and analysed using ELISA, flow cytometry, haematology and biochemistry.

Results: On the 42^nd dol, as the content of larvae meal in the chickens' diets increased, the birds' body weights decreased significantly. The substitution of the protein source had no effect on the haematological markers. In chicks that received larvae meal, there was a decrease in creatine kinase activity and phosphorus levels and an increase in calcium and uric acid levels in serum. Raising the proportion of full-fat HI larvae meal in the diet raised the percentage of T CD3⁺CD8a⁺ cells and lowered that of T CD3⁺CD4⁺ cells in both sample types. Chickens fed larvae meal had significantly lower post-vaccination anti-infectious bronchitis virus antibody titres.

Conclusion: The poorer production results and impaired health in experimental birds may indicate lower than 50% protein substitution with full-fat HI larvae meal to be optimal.