Dietary administration of the extract of Rhodobacter sphaeroides WL-APD911 enhances the growth performance and innate immune responses of seawater red tilapia (Oreochromis mossambicus x Oreochromis niloticus)

A commercial carotenoid product from the extract of probiotic Rhodobacter sphaeroides mutant strain WL-APD911 (Lycogen (TM)) contains neurosporene, xi-carotene, spheroidenone and methoxyneurosporene rather than lycopene. In the present study, Lycogen (TM) was used to improve the growth performance of seawater red tilapia (Oreochromis mossambicus x Oreochromis niloticus) for 7 weeks. The results showed that dietary supplementation with 1.0% Lycogen (TM) in seawater tilapia did not cause changes in body length but significantly increased muscle weight, weight gain, the specific growth rate (SGR) and the feed conversion ratio (FCR). Because there were no intergroup differences in the proximate composition of the fish muscle, the increased body weight of Lycogen (TM)-supplemented tilapia might have resulted from muscle growth instead of changes in muscle composition. An analysis of the expression levels of growth-associated genes, i.e., growth hormone receptor 1 (GHR1) and insulin growth factor-1 (IGF-1), showed that an alternative splicing form of GHR1 accumulated to a significant extent in the muscle of tilapia fed with a Lycogen (TM)-supplemented diet. In addition, innate humoral responses, reflected by lysozyme activity and alternative complement activity (ACH(50)), also significantly increased in the sera of Lycogen (TM)-treated tilapia. The present study suggests a potential application of the biomaterial Lycogen (TM) in the aquaculture field: to enhance tilapia growth performance via immune regulation. (C) 2013 Elsevier B.V. All rights reserved.