Dietary Tartaric Acid Improves Growth Performance, Gut Microbiota, Digestive Enzyme Activities, Hemolymph Immunity, Antioxidant Markers, and Disease Resistance against Vibrio parahaemolyticus in Pacific White Shrimp

Tartaric acid (TA) is an organic acid whose properties in aquaculture have not yet been comprehensively studied. In the current research, the effect of dietary TA on growth indices, gut microbiota, the level of digestive enzymes, antioxidant and immunological markers, and survival rate following immersion challenge with Vibrio parahaemolyticus (14 days) in Litopenaeus vannamei were investigated. To achieve this, 600 shrimp (3.26 +/- 0.05 g) were tested with pellets supplemented with five distinct concentrations of TA including 0 (TA0), 2.5 (TA2.5), 5 (TA5), 7.5 (TA7.5), and 10 g/kg (TA10) for 56 days. The results showed that the growth performance, feed utilization, gut lactic acid bacteria (LAB) count, and activity of digestive enzymes were markedly elevated in the groups receiving diets incorporated with 5 and 7.5 g/kg of TA. The highest total hemocyte count (THC), hyaline cell (HC), and semi-granular cell (SGC) counts were detected in shrimp fed with the TA7.5 diet. Hemolymph immune responses including LYZ (lysozyme), alkaline phosphatase (AKP), acid phosphatase (ACP), and phenol oxidase (PO) activities were significantly enhanced in all TA-treated groups. Dietary TA7.5 significantly boosted all antioxidant enzymes. In addition, malondialdehyde (MDA) content illustrated a significant decrease in shrimp fed with diets supplemented with 2.5-10 g/kg TA when compared with specimens fed with TA0. The survival rate following the immersion challenge with Vibrio parahaemolyticus markedly increased in all shrimp treated with 2.5-10 g/kg TA compared to TA0, irrespective of the dosage. However, the dietary inclusion of TA7.5 resulted in the highest survival rate. Based on the outcomes, dietary TA, especially at the concentration of 7.5 g/kg, is proposed to promote the growth performance and immunological indicators of L. vannamei.