Positive and synergistic effects of oxytetracycline and β-glucan on non-specific immune responses in the white shrimp, Litopenaeus vannamei (Boone, 1931) (Dendrobranchiata, Penaeidae)

Abstract

This study was to examine the immunomodulatory effects of oxytetracycline (OTC) on the white shrimp Litopenaeus vannamei (Boone, 1931). Immune parameters were not suppressed by OTC treatment in haemocytes in vitro. A total of 96 healthy shrimp were divided into four groups. Group 1 was the control group. Group 2 received 50 mg OTC/kg body weight/day. Group 3 received 1 g β-glucan/kg feed. Group 4 received 50 mg OTC/kg body weight/day and 1 g/kg β-glucan. OTC residues were more highly accumulated in the hepatopancreas than in muscle tissue during the rearing period, and the addition of β-glucan prolonged the retention time of OTC in the muscle tissue. Additionally, dietary administration of OTC in combination with β-glucan facilitated the excretion of OTC from the hepatopancreas. Shrimp that orally ingested OTC alone had an elevated total haemocyte count, phagocytosis, superoxide anion production and prophenoloxidase activity, and these immunostimulatory effects were further enhanced in shrimp receiving OTC in combination.