Optimal form of yeast cell wall promotes growth, immunity and disease resistance in gibel carp (Carassius auratus gibelio)

A 63-day feeding trial was conducted to explore dietary yeast cell wall (YCW) on growth, immunity and disease resistance against Aeromonas hydrophila in gibel carp (Carassius auratus gibelio var. CAS III) (initial body weight: 8.49 +/- 0.27 g). Four isonitrogenous and isoenergetic diets were formulated to contain 0 % or 0.4 % three types of yeast cell wall (YCW) (termed as YCW0, YCW1, YCW2 or YCW3, respectively). Fish were randomly divided into 4 feeding groups in triplicates of 22 fish in each tank. Results showed that the highest final body weight was observed in fish fed YCW3 diet than the control (P < 0.05). Compared to the control group, significantly higher FE was found in groups of YCW2 and YCW3 (P 0.05). There were no significant differences in feeding rate, specific growth rate, protein retention rate and energy retention rate among treatments (P 0.05). The relative expressions of TNF-alpha 1 and IL-8 were not significantly affected by YCW inclusion in the diet (P 0.05). Hepatic IL 18 and TGF-8 expressions were significantly down-regulated in the fish fed YCWs (P < 0.05). Furthermore, dietary administration of YCW1 and YCW3 could to some extent improve disease resistance against bacterial challenge. Based on growth performance and immunity, 0.4 % YCW3 was recommended in the gibel carp diet.