Systemic and hepatic responses of early-stage broilers fed diets incorporating spray-dried, extruded or pancreatin-supplemented extruded Chlorella vulgaris

High dietary inclusion of Chlorella vulgaris may reduce soybean meal use, but its physiological effects depend on dose, exposure period and processing. This study evaluated systemic and hepatic responses of broilers fed 15% C. vulgaris from days 7 to 35 and tested the incremental response to pancreatin after biomass extrusion. A total of 120 male Ross 308 broilers were allocated to 40 pens and four diets: a maize–soybean control, 15% spray-dried C. vulgaris , 15% extruded C. vulgaris , or the extruded diet plus 0.30% pancreatin. Growth was evaluated by pen, and one bird per pen was sampled on day 35 for haematology, plasma biochemistry and hepatic lipid, fatty acid, pigment, vitamin E homologue and mineral analyses. Final body weight, average daily gain and feed conversion ratio did not differ among diets (P > 0.05), whereas feed intake was greater with extruded biomass plus pancreatin than with spray-dried biomass (P = 0.013). All C. vulgaris diets reduced relative liver weight by at least 18% and hepatic iron by more than 50% (P < 0.001), altered circulating lipids and hepatic fatty acid proportions, and increased hepatic vitamin E homologues and microalgal pigments. Pancreatin produced no consistent additional response when added to extruded biomass; however, its independent effect and interaction with extrusion could not be estimated because pancreatin was only tested in the extruded diet. Overall, 15% C. vulgaris from day 7 maintained growth performance but induced marked systemic and hepatic changes including a reduction in hepatic iron and altered fatty acid, vitamin E homologue and microalgal pigment profiles. These findings highlight that growth performance alone does not capture the physiological effects of dietary C. vulgaris .