The effects of dietary fermented cassava on the blood constituents and production parameters of broiler chickens have been reported with variable outcomes. Therefore, this investigation aimed to explore the impacts of dietary fermented cassava on growth traits, blood constituents, visceral organ, and carcass characteristics of broiler chickens. Four databases were searched for studies that assessed responses of broiler chickens dietary fermented cassava. Eleven articles were used for the investigation, and data generated were analysed using OpenMEE software. A random effects model was used, and effect sizes were presented as standardised mean difference (SMD) at a 95 % confidence interval (CI). Sources of heterogeneity were evaluated using the following modifiers: broiler strain used, cassava form, feeding duration, type of microbes used for the fermentation, and inclusion level of cassava. Results indicate that fermented cassava-based diets increased feed intake (SMD = 0.38; 95 % CI: 0.11, 0.65; P = 0.006), feed conversion ratio (SMD = 1.26; 95 % CI: 0.91, 1.61; P < 0.001), white blood cells (SMD = 1.26; 95 % CI: 0.54, 1.98; P < 0.001), total serum protein (SMD = 1.23; 95 % CI: 0.41, 2.05; P = 0.003), serum cholesterol (SMD = 0.43; 95 % CI: 0.01, 0.85; P = 0.050), serum creatinine (SMD = 2.53; 95 % CI: 0.53, 4.53; P = 0.013), and serum uric acid (SMD = 4.33; 95 % CI: 6.25, 2.41; P < 0.001), but lowered average daily gain and carcass yield, taking heterogeneity into account. Results reveal that studied modifiers were responsible for the inconsistent results among authors. In conclusion, dietary fermented cassava negatively influenced carcass yield, growth performance, and aspects of blood indices of broiler chickens, but did not affect abdominal fat content, visceral organ weights, and cut-part weights. However, more innovative research is needed to improve the feeding quality of cassava using other biotechnological tools in order to maximise its potential as an energy source in broiler chickens.
