Effect of ascidian (Halocynthia roretzi, Drasche 1884) tunics carotenoids on enhancing growth and muscle coloring of sea-reared rainbow trout (Oncorhynchus mykiss, Walbaum 1792)

Abstract

A 120 days trial was conducted to investigate the effect of sea squirt (Halocynthia roretzi, Drasche 1884) tunic's carotenoid to sea-reared rainbow trout (Oncorhynchus mykiss, Walbaum 1792) growth and muscle color. Sea-rearing was done at Tongyeong sea area, Korea. Three dietary treatments, namely control (C), CT, and AT, were administered to 6 groups of fish (n = 490-520). C was given basal diet which has contained 40 mg kg(-1) of astaxanthin. A further inclusion of 10 mg kg(-1) canthaxanthin was added to diet of CT, while AT's feed was supplemented with 10 mg kg(-1) H. roretzi tunics carotenoids extract. The result revealed that AT has the highest final weight (1119.2 +/- 82.4 g) compare to those of C (881.0 +/- 121.2 g) and CT (1068.2 +/- 4.3 g). The specific growth rate (SGR) of AT (1.0 +/- 0.07%/day) was significantly higher than C (0.7 +/- 0.22%/day) and CT (0.7 +/- 0.25%/day) while the feed conversion ratio (FCR) were 1.5 +/- 0.6, 1.4 +/- 0.6, and 1.2 +/- 0.1 for C, CT and AT respectively. The hepatosomatic index (HSI) and Viscerosomatic index (VSI) of all groups showed no significant difference (p > 0.05). The muscle color was also positively affected by the treatments, CT and AT were significantly different from C (p<005). The initial muscle color score was 1.7 +/- 0.0 and the final scores were 3.4 +/- 0.2, 5.6 +/- 0.1, and 5.7 +/- 0.0 for C, CT, and AT respectively. Moreover, muscle carotenoids content of AT (8.5 +/- 0.2 mg kg(-1)) was significantly higher (p < 0.05) than those of CT (6.9 +/- 0.3 mg kg(-1)) and C (6.1 +/- 0.2 mg kg(-1)). Astaxanthin evidently is the most prominent carotenoid present in the muscle from all groups. (C) 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license.