Replacement of corn by sorghum and phytase supplementation in silver catfish (Rhamdia quelen) diets: growth performance, physiological variables and bone mineralization

Abstract

ABSTRACT This study aimed at assessing productive growth performance, blood physiology, intestinal histology, body composition and bone mineralization parameters of silver catfish juveniles fed diets containing different inclusion levels of sorghum, considering three combinations (0%, 50% or 100%), supplemented or not with phytase enzyme (0 and 1500 FTU kg−1). The apparent feed conversion and specific growth rate were benefited by supplemented diets (P < 0.05). The highest protein efficiency rate was obtained for the supplemented diet containing corn (P < 0.05). The viscerosomatic index was lower when corn/sorghum diet (P < 0.05) was offered, whilst the hepatosomatic index was lower in corn and corn/sorghum diets regardless of supplementation (P < 0.05). Regarding blood parameters, variations were observed (P < 0.05), however they were kept within the limits for the species. Histomorphometry variables also displayed variations, which were observed in fish fed with sorghum and sorghum/corn diets, supplemented or not (P < 0.05). Proximate composition of carcass varied for both aether extract and mineral matter for supplemented diets (P < 0.05). A variation of Ca content (P < 0.05) regarding bone mineralization was observed when corn and sorghum were used in the same proportion. Sorghum replacement of corn in diets for R. quelen may be a feasible alternative, and phytase supplementation with improves fish performance.