A commercial carotenoid product from the extract of probiotic Rhodobacter sphaeroides mutant strain WLAPD911
(Lycogen™) contains neurosporene, ξ-carotene, spheroidenone and methoxyneurosporene rather
than lycopene. In the present study, Lycogen™ was used to improve the growth performance of seawater
red tilapia (Oreochromis mossambicus × Oreochromis niloticus) for 7 weeks. The results showed that dietary
supplementation with 1.0% Lycogen™ 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™-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 themuscle of tilapia fed with a Lycogen™-supplemented diet. In addition,
innate humoral responses, reflected by lysozyme activity and alternative complement activity (ACH50), also
significantly increased in the sera of Lycogen™-treated tilapia. The present study suggests a potential application
of the biomaterial Lycogen™ in the aquaculture field: to enhance tilapia growth performance via immune
regulation.