Prebiotics in Finfish: An Update - Aquaculture Nutrition: Gut Health, Probiotics and Prebiotics - page 365

The immunomodulatory effects of dietary inulin on rainbow trout were investigated by
Sheikholeslami et al . (2007). Fish (34 ± 4 g) were fed inulin at two inclusion levels (5 and
20 g kg −1 ) for 8 weeks. At the end of the trial, immune parameters including serum lysozyme
activity, IgM, peripheral leukocyte levels and resistance against Streptococcus sp. were mea-
sured. Their results confirmed significant increases of lysozyme activity IgM as well as ele-
vated leukocyte levels and resistance against Streptococcus sp. in the prebiotic groups. In a
later study, Akrami et al . (2009a) reported the lowest SGR of juvenile rainbow trout after
8 weeks when the fish were fed inulin supplemented diets (at 10, 20 and 30 g kg −1 ) compared
to those on the basal diet (not supplemented with inulin). Furthermore, the authors reported
no significant difference in FCR, feed efficiency (FE), PER, CF and survival.
In a recent study, Rehulka et al . (2011) reported results from a 105 day experiment, where
the effect of dietary scFOS on rainbow trout (initial weight 240 ± 34.9 g) growth and plasma
biochemical parameters was determined. Inclusion of scFOS at 1 g kg −1 did not significantly
affect SGR, FCR and survival. The results of the biochemical parameters indicated significant
differences in creatinine, Na + and alkaline phosphatase (ALP, involved in intestinal mucosal
defence). Recently, Ortiz et al . (2012) evaluated the effects of inulin and FOS on growth per-
formance, body chemical composition and some intestinal bacteria in rainbow trout reared in
raceways for 7 weeks. The prebiotic supplementation significantly improved body weight com-
pared with the control while FCR decreased with prebiotics inclusion. However, fillet crude
protein content decreased in the prebiotic fed fish ( P = 0.009). The effect of prebiotics on
some culturable gut bacteria isolated from the intestinal contents was also investigated. Nei-
ther inulin nor FOS supplementation had any significant effect on Aeromonas , Pseudomonas
and Gram-positive bacterial levels. In contrast Vibrio spp. were not detected when trout were
fed inulin. As no effort was made to identify the gut bacteria to species level, we recommend
that this is included in further studies.
14.3 GADOIDS
To our knowledge the only study evaluating the effect of prebiotics (MOS) on Atlantic cod
( Gadus morhua L.) was carried out by Lokesh et al . (2012). In this study, the expression of
inflammatory (IL1β, IL8 and IFNγ) and anti-inflammatory (IL10) cytokine genes in anterior
intestine, posterior intestine and rectum were investigated using qPCR both prior, and post,
challenge with Vibrio ( Listonella ) anguillarum . Compared to the control fed fish MOS fed fish
(1gkg −1 of diet) displayed significantly higher levels of IFNγ mRNA in the anterior intestine
prior to challenge and significantly higher IL1β mRNA levels in the posterior intestine post
challenge. Furthermore relative to the pre-challenge levels, MOS fed fish displayed signifi-
cantly higher expression of IL1β in the posterior intestine and rectum and IL8 in the rectum,
post challenge. This was not the case for the control fed fish. These results indicate that MOS
may influence the localized intestinal immune readiness of cod, and the authors concluded that
further studies are needed to clarify the mechanisms linked to these pathways.
14.4 ACIPENSERIDAE
With the decline in wild sturgeon populations there has been great interest in farming various
sturgeon species for restocking, caviar and meat. Total sturgeon aquaculture production has