Effects of Microencapsulated Organic Acid and Their Salts on Growth Performance, Immunity, and Disease Resistance of Pacific White Shrimp Litopenaeus vannamei

Abstract

A 63-day trial with Pacific white shrimp (0.33g) was conducted to assess the effects of two forms of organic acid (COMP), free acids (OA) and acid salts (OS) microencapsulated (ENCAP) with hydrogenated fat (HF), hydrogenated fat + alginate (HA), wax esters – (WE), and double coating of HA and WE (HAWE) on their growth performance, nutrient utilization, digestive enzyme, immune response and resistance to pathogenic Vibrio parahaemolyticus. A high fishmeal (FM) diet containing 200 g/kg FM and a low FM diet containing 130 g/kg FM and 120 g/kg soybean meal were formulated as positive (PC) and negative control (NC), respectively. Eight other diets were formulated supplementing NC diet with microencapsulated OA (OAHF, OAHA, OAWE, OAHAWE) and OS (OSHF, OSHA, OSWE, OSHAWE). All diets were formulated to be iso-proteic (36.9% CP) and iso-energetic (16.1 MJ/g). Total 1600 shrimps were distributed to 40 tanks (40 shrimps/tank and 4 replicates/treatment). Shrimp fed diets containing OA showed significantly lower feed intake (P = 0.017) and FCR (P = 0.012), and higher protein retention efficiency (P = 0.016) than those fed the OS diets. Among the ENCAPs, significant difference was observed in serum malondialdehyde (P = 0.026) where HF showed the lowest level (6.4 0.3 mmol/L). Significant interactions between COMP and ENCAP were observed in lipid deposition (P = 0.047), serum alkaline phosphatase and acid phosphatase (P < 0.0001), and hepatopancreatic and serum phenol oxidase (P < 0.0001). Despite no differences, the 96-h mortality in all treatment diets (45% - 56%) was significantly lower compared to the NC diets (63%) under pathogenic vibrio parahaemolyticus challenge tests. Overall score combining the parameters shows that shrimp fed the OA diets with HF microencapsulation performed better compared to those fed diets with OS and other microencapsulation materials.