Seaweeds are functional feed sources that contain biocompounds with growth-stimulating, antimicrobial and meat-enhancing properties. However, the presence of non-starch polysaccharides such as cellulose, hemicellulose, pectin and xylan may limit its utilization in broiler diets. Thus, this study evaluated the effects of pretreating dietary green seaweed (Ulva sp.) with a fibrolytic enzyme mixture on physiological and meat quality parameters of Cobb 500 broiler chickens. Three hundred and thirty, two-week old male chicks (318.9 +/- 16.12 g live weight) were evenly and randomly placed in 30 replicate pens (experimental units) to which five isonitrogenous and isoenergetic diets were randomly allotted. Experimental diets were commercial grower and finisher diets containing seaweed pre-treated with a fibrolytic enzyme mixture of cellulase, hemi-cellulase, arabanase, beta-glueanase and xylanase, at the rate of 0 (EZ0), 2.0 (EZ20), 5.0 (EZ50), 7.5 (EZ75) and 12.0 g/kg (EZ120). Growth performance, blood indices, visceral organs, and carcass and meat quality parameters were determined. No week x diet interaction effect (P > 0.05) on average weekly feed intake (FI), body weight gain (BWG), and feed conversion efficiency (FCE) was observed. Neither linear nor quadratic trends (P > 0.05) were observed for overall FI, growth performance, haematological and serum biochemical parameters as well as visceral organ weights in response to incremental levels of fibrolytic enzyme pre-treatment of seaweed. However, there was a linear increase in hot [R-2 = 0.176, P = 0.033] and cold [R-2 = 0.164, P = 0.040] carcass weights in response to increased enzyme pre-treatment rates. Breast meat lightness measured immediately after slaughter (L*(i)) linearly decreased [R-2 = 0.147, P = 0.022] as enzyme levels increased. Diets with enzyme-treated seaweed promoted higher (P< 0.05) carcass weights compared to the untreated seaweed-containing control diet. It was concluded that pre-treatment of seaweed meal with an exogenous fibrolytic enzyme mixture did not improve growth performance, blood parameters, and meat quality traits in broiler chickens. An optimum fibrolytic enzyme treatment level for seaweed could not be determined, suggesting a need to investigate levels beyond the maximum treatment level of 12 g/kg used in this study.
