Assessment of fish protein hydrolysate as a substitute for fish meal in white shrimp diets: Impact on growth, immune response, and resistance against Vibrio parahaemolyticus infection.

This study investigated the effects of fish protein hydrolysate derived from barramundi on growth performance, muscle composition, immune response, disease resistance, histology and gene expression in white shrimp (Penaeus vannamei). In vitro studies demonstrated FPH enhanced mRNA expressions of key immune-related genes and stimulated reactive oxygen species (ROS) production and phagocytic activity in shrimp hemocytes. To evaluate the effects of substituting fish meal with FPH in vivo, four isoproteic (43 %), isolipidic (6 %), and isoenergetic diets (489 kcal/100 g) were formulated with fish meal substitution levels of 0 % (control), 30 % (FPH30), 65 % (FPH65), and 100 % (FPH100). After 8-week feeding, the growth performance of FPH65 and FPH100 were significantly lower than that of control and FPH30 (p < 0.05). Similarly, the midgut histological examination revealed the wall thickness and villi height of FPH100 were significantly lower than those of control (p < 0.05). The shrimps were received the challenge of AHPND + Vibrio parahaemolyticus at week 4 and 8. All FPH-fed groups significantly enhanced resistance against Vibrio parahaemolyticus at week 4 (p < 0.05). However, this protective effect diminished after long-period feeding. No significant difference of survival rate was observed among all groups at week 8 (p > 0.05). The expressions of immune-related genes were analyzed at week 4 before and after challenge. In control group, V. parahaemolyticus significantly elevated SOD in hepatopancreas and Muc 19, trypsin, Midline-fas, and GPx in foregut (p < 0.05). Moreover, hepatopancreatic SOD of FPH65 and FPH100 were significantly higher than that of control before challenge (p < 0.05). Immune parameters were measured at week 8. Compared with control, the phagocytic index of FPH 30 was significantly higher (p < 0.05). However, dietary FPH did not alter ROS production, phenoloxidase activity, phagocytic rate, and total hemocyte count (p > 0.05). These findings suggest that FPH30 holds promise as a feed without adverse impacts on growth performance while enhancing the immunological response of white shrimp.

Metabolomic assessment of African snail (Achatina fulica) meal on growth performance of giant river prawn (Macrobrachium rosenbergii).

This study aimed to investigate the effects of replacing fishmeal (FM) with African giant snail (Achatina fulica) meal (SM) on the growth performance of giant river prawn (Macrobrachium rosenbergii), as well as to analyze the associated metabolomic changes. Six diets were formulated, replacing FM with SM at different inclusion levels ranging from 0 % to 100 %. Growth performance and feed conversion ratio of prawns fed diets with FM replaced by SM up to 80 % were not significantly different from control. In contrast, significantly decreased growth performance and higher feed conversion ratio (FCR) occurred with diets containing 100 % SM. To gain insights into the metabolic regulation of prawns fed different diets, a 1H NMR metabolomics approach was used to assess the metabolic changes in prawns fed diets containing 0 % and 80 % SM. The results revealed up-regulated metabolites significantly involved in several metabolic pathways, including alanine, aspartate, and glutamate metabolism; citrate cycle (TCA cycle); aminoacyl-tRNA biosynthesis; and valine, leucine, and isoleucine biosynthesis. These findings imply that including SM in the diet might modulate the regulation of muscle amino acids and tRNA synthesis, suggesting a potential impact on protein biosynthesis mechanisms. Additionally, alterations in the TCA cycle may reflect changes in carbon utilization, potentially contributing to the growth performance of giant river prawns when fishmeal is replaced with SM without adversely affecting their growth. In conclusion, this study demonstrated that SM could be a promising alternative protein source in aquafeed. The metabolomic approach provides valuable insights into the metabolic changes in prawns fed different diets, aiding in the development of more effective aquafeeds in the future. The study's limitations, such as the simplified diet formulation and the limited scope of the metabolomic analysis, were acknowledged and discussed, highlighting the need for further research to build upon these findings.