Effect of dietary tributyrin on growth, feed utilization, innate immunity and disease resistance against Vibrio parahaemolyticus in Pacific white shrimp (Penaeus vannamei)

This study evaluated the effects of dietary tributyrin (TB) on the growth, feed utilization, innate immunity, digestive enzyme activity, expression of genes related to non-specific immunity, diet digestibility, and disease resistance against Vibrio parahaemolyticus in Pacific white shrimp (Penaeus vannamei). A basal diet (Con) containing 20% fish meal was prepared according to the essential nutrient requirement of P. vannamei. TB (60% purity) was incorporated into Con diet at product inclusion levels of 0.05% (TB5), 0.10% (TB10), and 0.20% (TB20), corresponding to 0.03%, 0.06%, and 0.12% active TB equivalent, respectively. Four replicate groups of shrimps (mean weight, 0.5 ± 0.0 g) were fed one of these diets for 8 weeks. Weight gain and specific growth rate were significantly higher in the TB10 group compared to the Con group (p < 0.05). Feed conversion ratio was significantly lower in the TB5 and TB20 groups than in the Con group (p < 0.05). Activities of phenoloxidase, lysozyme, antiprotease, and glutathione peroxidase in hemolymph were significantly higher in the TB10 and TB20 groups than in the Con group (p < 0.05). Phagocyte activity and superoxide dismutase activities were significantly higher in all TB-added groups compared to the Con group (p < 0.05). The expression levels of prophenoloxidase and Toll-like receptor 3 were significantly higher in the TB20 group than in the other test groups (p < 0.05). Crustin gene expression was significantly higher in the TB-supplemented groups compared to the Con group (p < 0.05). Diet digestibility of dry matter and protein in all TB-supplemented groups, and lipid digestibility in the TB20 group, were significantly higher than those in the Con group (n = 3, p < 0.05). Compared to the Con group, trypsin activity in the TB10 and TB20 groups, and amylase activity in the TB20 group exhibited significantly higher values (p < 0.05). In the challenge test against V. parahaemolyticus, Kaplan-Meier survival analysis indicated no significant difference among treatments (n=3, p > 0.05). Based on quadratic regression results, the estimated optimal content of TB in the Pacific white shrimp diet is 0.113% (95% CI: 0.00%-0.19%) to obtain maximum weight gain.