Effects of Dietary Tuna Viscera Hydrolysate Supplementation on Growth, Intestinal Mucosal Response, and Resistance to Streptococcus iniae Infection in Pompano (Trachinotus blochii)

The effects of tuna viscera hydrolysate (TVH) on juvenile pompano Trachinotus blochii, growth performance, nutritional response, intestinal and liver health, and resistance to Streptococcus iniae were investigated in this study. Five isonitrogenous and isocaloric diets (protein 46.0%, lipid 10.0%) were formulated in which TVH was added to replace fishmeal protein at levels of 0 (control), 30, 60, 90, and 120 g kg(-1), labelled as TVH0, TVH05, TVH10, TVH15, and TVH20, respectively. Triplicate groups of pompano were fed the respective diets for ten weeks. The results showed that fish fed diets containing TVH10 produced significantly higher final body weight and specific growth rate in comparison to the fishmeal control (P < 0.05). Dietary TVH did not produce any effect on feed utilisation, somatic indices, and proximate composition of juvenile pompano (P > 0.05). While most amino acids were unchanged by the dietary inclusion of TVH, phenylalanine and valine levels were significantly lower in the fish fed TVH20 diet compared to the control. Fish fed the TVH20 diet had significantly lowered total serum protein compared to the TVH10 treatment, whereas other biochemical parameters in the blood did not show any difference among treatments. The intestinal histology indicated a significant increase in goblet cell numbers in fish fed TVH10 diet. Fish fed diet supplemented with TVH showed the highest disease resistance against Streptococcus iniae after 14 days of challenge. Based on a quadratic regression between final body weight and dietary TVH levels, the optimum TVH was calculated to be 10% or 60.0 g kg(-1) for maximum growth performance when fed to pompano.