Bond Brown Layer (BBL) pullets (n = 200, 18 weeks old) were randomly assigned to 10 dietary treatments involving biochar, zeolite and bentonite at nil, 1%, 2%, and 4% w/w supplementation of commercial layer feed. Each treatment was applied to four cages, with five birds per cage, a total of 20 birds per treatment. Birds were maintained on these diets for 25 weeks. Feed conversion ratio was significantly improved (P = 0.001) with biochar-supplemented feed compared with the control and other treatments. Average egg weight was also significantly improved in the treatment groups compared with the control; however, shell weight, shell breaking strength, shell thickness, shell deformation and shell reflectivity, and internal egg-quality traits of albumen height and Haugh unit were not consistently different (P > 0.05). Yolk colour score was decreased significantly (P = 0.001) with the use of increased rate of additives. Intestinal villi height and crypt depth were increased on amended diets. Egg yield was decreased when birds were placed on a fungal contaminated feed. The feed amendments ameliorated this effect, with the best result achieved on a 2% biochar diet. Improved egg production was also noted under commercial certified organic production conditions trialling 2% biochar feed supplementation compared with the control. Thus, supplementation of feed with biochar, zeolite and bentonite improved production performance traits of egg yield and feed conversion ratio, with these additives potentially acting as detoxifiers or inhibiting growth of microbial pathogens, slowing digestion or altering the gut anatomy and microbiota to improve feed conversion ratio. [ABSTRACT FROM AUTHOR]