Cassava by-products in broiler diets: effects on growth performance based on a systematic review

The use of cassava (Manihot esculenta Crantz) by-products as alternative energy sources in broiler diets has increased, but their effects on growth performance remain inconsistent across studies. This systematic review evaluated the effects of replacing corn with cassava by-products (cassava meal, pulp, and bagasse) on broiler performance using a qualitative direction-of-effect synthesis. A total of 36 studies published between 2005 and 2025 were included, comprising 187 dietary comparisons. Most studies were conducted in Brazil (36.1%), Nigeria (25.0%), and Indonesia (18.2%). Because measures of variability were frequently unavailable, responses in feed intake (FI), body weight gain (BWG), and feed conversion ratio (FCR) were classified as positive, negative, or neutral relative to the reference treatment. Feed intake was predominantly unaffected (54.4% neutral responses). For BWG, negative responses were most frequent (49.2%), followed by neutral (44.4%) and positive responses (6.4%). For FCR, neutral (45.5%) and negative (44.4%) responses occurred at similar frequencies, whereas positive responses accounted for 10.2% of comparisons. Negative responses became more frequent as dietary inclusion levels increased, particularly for BWG and FCR, and were most evident at inclusion levels above 25%. Most studies (86.1%) were classified as having a high risk of bias or some concerns, and measures of variability were frequently not reported, limiting quantitative comparison of effect estimates and the strength of inference. Overall, cassava by-products were more frequently associated with reduced growth performance at higher dietary inclusion levels, although responses varied according to by-product type, processing method, inclusion level, and study conditions. These findings support cautious dietary formulation and highlight the need for standardized experimental reporting to better define safe and effective inclusion levels for individual cassava by-products in broiler nutrition.