Effects of <i>Spirulina platensis</i> supplementation on growth performance, caecal microflora, intestinal morphology, antioxidant status and lipogenic related gene expression in broiler chickens

1. An experiment was conducted to evaluate the effects of different levels of dried Spirulina platensis (SP) on growth performance, caecal microflora, intestinal morphology, antioxidant status and particularly the expression of major lipogenic genes in the liver of broiler chickens.2. Three hundred Ross 308 male broiler chicks were assigned to one of five treatments with six replications and 10 birds each based on a completely randomised design. Experimental diets were maize-soy based and included 0, 0.25, 0.5, 0.75 or 1% SP and fed to birds for 42 d. Two birds per replicate were selected for the evaluation of carcass characteristics, caecal microflora, intestinal morphology, serum and liver antioxidant status and lipogenic gene expression.3. Body weight gain and feed conversion ratio were significantly improved in chickens fed a diet containing 1% SP compared to the control group (p < 0.05). Significant improvements in carcass (p < 0.05) and breast (p < 0.01) yield in the chickens fed diets containing 0.75 and 1% SP were observed compared to the control group, and, with increasing SP, abdominal fat decreased linearly (p < 0.05).4. Escherichia coli counts in the caecum of birds fed 0.75 and 1% SP decreased significantly compared to the control group (p < 0.05). Inclusion of 0.5, 0.75 and 1% SP decreased malondialdehyde level in liver (p < 0.05). Gene expression of ∆-6-desaturase and ∆-9-desaturase was higher in the birds fed 0.5% or higher SP levels compared to control group.5. This study showed that adding 1% SP to the diet of broiler chickens improved production efficiency by improving growth performance, antioxidant status and intestinal health. This level of supplementation showed significant potential in improving carcass quality and reducing abdominal fat by regulating the expression of key genes in the fatty acid metabolism pathway.