High inclusion of Chlorella vulgaris in broiler diets improves feed efficiency and liver n‑3 fatty acid profile: effects of extrusion and enzyme super-dosing.

1. Chlorella vulgaris (C. vulgaris) is a highly nutritious and sustainable feed ingredient, but its rigid cell wall limits nutrient availability and digestibility.2. To evaluate the effects of incorporating C. vulgaris at 15% dietary inclusion in broiler diets during a three-week finishing period (days 14-35), four experimental diets were tested: a control maize-soybean meal diet (CON), a 15% C. vulgaris diet (CHL), a 15% C. vulgaris plus 0.30% pancreatin diet (CHLENZ) and a 15% extruded C. vulgaris diet (CHLEXT).3. Growth performance, haematological variables, blood biochemistry, hepatic lipid, pigment and mineral contents were analysed. To date, no study has explored the effects of C. vulgaris at this inclusion level on broiler plasma metabolites and hepatic lipid composition, either extruded or supplemented with super-dosing pancreatin, both aimed at enhancing nutrient utilisation.4. All C. vulgaris diets maintained or improved growth performance, with CHLEXT significantly enhancing final body weight, body weight gain and feed conversion ratio. Most haematological markers were unaffected, although extrusion lowered granulocyte and elevated lymphocyte counts relative to CHL and CHLENZ. Biochemical changes included reduced triacylglycerol levels and elevated glucose in all microalga-fed groups. Additionally, creatine levels were reduced in the CHL and CHLENZ groups compared to the CON group. Hepatic fatty acid profile showed reduced n-6/n-3 polyunsaturated fatty acid ratio in all C. vulgaris-fed groups. Mineral content showed a decrease in hepatic magnesium in the CHLEXT group compared to the CON group.5. A 15% dietary inclusion of C. vulgaris is nutritionally viable and metabolically beneficial for broilers.