Interactions between dietary protein level and water temperature on the growth performance, innate immunity and disease resistance of juvenile abalone Haliotis discus hannai Ino

Abstract

A 100-day feeding trial was performed to examine the effects of dietary protein level, water temperature and their interactions on the growth performance, innate immunity and disease resistance of abalone Haliotis discus hannai with an initial body weight of 12.20 ± 0.1 g and an initial shell length of 42.64 ± 0.29 mm. With graded levels of dietary protein (9.33%, 27.53% and 40.42%, respectively), three isolipidic and isoenergetic diets were made and used in two water temperatures (17 °C and 23 °C) in a form of a 3 × 2 factorial design. The results indicated that the weight gain rate (WGR) and daily increment in shell length of abalones (DISL) were significantly higher in 27.53% of dietary protein level at both 17 °C and 23 °C water temperatures. At 17 °C and 23 °C of water temperatures, 27.53% of dietary protein significantly increased the trypsin and α- amylase as well as decreased the malondialdehyde content and glutamate dehydrogenase activities of abalone. Dietary protein and water temperature interact significantly with WGR and α-amylase. The histological analysis of abalone’s digestive gland showed that 27.53% of dietary protein caused normal development at both water temperatures. The mRNA levels of tumor necrosis factor alpha, toll-like receptor 2 and 4, inhibitor κBα, iκb kinase α, myeloid differentiation primary response gene 88, interleukin1 receptor-associated kinase 4, caspase 3 and B-cell lymphoma protein-2-associated X protein were significantly down-regulated by 27.53% of dietary protein at 17 °C of water temperature. The total hemocyte counts (THC), respiratory burst (RB) and B-cell lymphoma 2 (Bcl-2) were significantly increased by 27.53% of dietary protein at 17 °C water temperature. Dietary protein and water temperature interact significantly with THC, RB and Bcl-2. The use of 27.53% of dietary protein at 17 °C of water temperature showed no mortality when challenged with V. parahaemolyticus. In conclusion, 27.53% of dietary protein level at 17 °C of water temperature activated the innate immunity by reducing inflammation and apoptosis response, hence increasing disease resistance in abalones after the Vibrio challenge test.