<i>Chlorella vulgaris</i> supplementation in broiler feed: effect on performance, intestinal health, meat quality and animal welfare under an <i>Eimeria</i> vaccine challenge

<i>1. Chlorella vulgaris</i>, a microalga rich in bioactive compounds, has antioxidant, anti-inflammatory and prebiotic properties. This study investigated the effects of 2% inclusion of autotrophic and heterotrophic <i>C. vulgaris</i>, both with and without pulsed electric field (PEF) processing, on the performance, intestinal health, and meat quality of broilers under a coccidiosis vaccine challenge.2. A total of 1008 Ross 308 male broilers were randomly divided into five treatment groups and fed diets containing either autotrophic or heterotrophic <i>C. vulgaris</i>, with or without PEF-processing, or a control diet without algae. The birds were subjected to a coccidiosis challenge through a high-dose times <i>Eimeria</i> vaccine. Performance variables and meat quality were recorded and intestinal health was assessed through ileal ovotransferrin levels as a marker of gut permeability, histological parameters and antioxidant capacity of blood plasma.3. Inclusion of <i>C. vulgaris</i> did not affect most performance parameters. However, a trend to an increased feed conversion ratio (FCR) was seen. Ovotransferrin concentrations and antioxidant capacity were higher for broilers fed with heterotrophic algae than with autotrophic algae. No significant differences in intestinal morphology were observed.4. Meat quality variables revealed that heterotrophic algae-fed broilers had darker, redder and more yellow breast meat. This was likely due to pigment uptake, but showed abnormalities like wooden breast and white striping.5. Supplementing with <i>C. vulgaris</i> can act as a functional feed additive in broiler production, particularly under conditions that simulate commercial stressors such as coccidiosis.