A 120-day feeding study on Chahua chicken No. 2, an indigenous Chinese breed, shows that polystyrene microplastics in poultry drinking water at 0.5 mg per day cut growth, worsened feed conversion, and rewired the gut barrier, inflammatory signals, and microbial community. Lower doses left growth intact but still shifted gut genes. Quick answer Polystyrene microplastics in poultry are not a future worry. In a 120-day trial, 0.5 mg per day of polystyrene microplastics in drinking water reduced body weight, average daily gain, and feed intake in Chahua chicken No. 2 at both 42 and 120 days, and pushed feed conversion toward worse at 120 days. The same dose weakened the…