Prebiotics in Finfish: An Update - Aquaculture Nutrition: Gut Health, Probiotics and Prebiotics - page 366

more than doubled in the past 5 years, exceeding 50,000 tonnes in 2011 (FAO FIGIS 2013).
Several studies have assessed the impact of dietary prebiotics (MOS, AXOS and inulin) on
the gut microbial community abundance and/or composition of sturgeons (Pryor et al . 2003;
Mahious et al. 2006a; Rurangwa et al . 2008; Delaedt et al . 2008); these findings are summa-
rized in Table 14.2 and discussed in the review of Ringø et al . (2010). More recently the effect
of prebiotics on beluga ( Huso huso ) and Siberian sturgeon ( Acipenser baerii ) growth perfor-
mance, immune response and GI microbiota has been evaluated in a number of studies (Pryor
et al . 2003; Mahious et al . 2006a; Delaedt et al . 2008; Rurangwa et al . 2008; Akrami et al .
2009b; Mohajer Esterabadi et al . 2010; Hoseinifar et al . 2011a; 2011b; 2011c; Ta'ati et al .
2011a; 2011b; Geraylou et al . 2012; Razeghi Mansour et al . 2012).
14.4.1 Beluga
Akrami et al . (2009b) investigated the effects of inulin supplementation (10, 20 and 30 g kg −1 )
on beluga juveniles (16.14 ± 0.38 g). Compared to the control fed fish, dietary inulin did not
affect growth performance or most of the haematological parameters investigated. Intestinal
bacterial analyses of the whole intestines (with contents) were carried out at 0, 4 and 8 weeks of
feeding. No significant difference in the level of CFU g −1 was present when using tryptic soy
agar medium but significantly lower levels were observed in the intestine of fish fed 3 g inulin
kg −1 on nutrient agar plates at week 4. However, this effect was not observed after 8 weeks of
feeding. After 4 weeks of feeding, LAB levels were significantly lower in the control group
and in the group fed 30 g inulin kg −1 compared to fish fed 20 g inulin kg −1 . In contrast, LAB
levels after 8 weeks feeding were significantly higher in fish fed 10 g inulin kg −1 compared to
control fish and fish fed 30 g inulin kg −1 . The authors concluded that inulin is not an appro-
priate dietary supplement for beluga. However, oligofructose, which is obtained by partial
enzymatic hydrolysis of inulin, showed different results on beluga juveniles (Hoseinifar et al .
2011a; 2011b). In two 8 week studies with beluga juveniles (18.77 ± 0.76 g), Hoseinifar et al .
(2011a; 2011b) studied the effect of dietary oligofructose (10, 20 and 30 g kg −1 )ongrowth
performance, haematological and serum biochemical parameters and intestinal microbiota.
Compared to the control, no significant effects were observed on growth performance. LAB
levels in the gut were significantly higher in fish fed 20 g kg −1 and the elevated LAB level
was able to persist for at least 1 week after reverting the prebiotic group back to a control diet
(Hoseinifar etal . 2011b). Haematological assessments revealed no significant effects on blood
cell counts, mean corpuscular volume, mean cellular haemoglobin, mean cell haemoglobin
concentration or serum lactate dehydrogenase, ALP, alanine aminotransferase and aspartate
aminotransferase activities. However 20 g dietary oligofructose kg −1 significantly increased
haemoglobin concentration, leukocyte levels and the proportion of lymphocytes and decreased
serum cholesterol level (Hoseinifar etal . 2011a). The difference between the results of the stud-
ies of Hoseinifar et al . (2011a; 2011b) and Akrami et al . (2009b) can possibly be attributed
to the prebiotic types and their degree of polymerization which directly affect fermentation
by the intestinal microbiota. However, as this has not been elucidated the topic merits fur-
ther investigations.
Hoseinifar et al . (2011c) evaluated the effects of dietary inactive yeast ( Saccharomyces
cerevisiae var. ellipsoideus ) product (10 and 20 g kg −1 ) on intestinal microbiota, haematology,
serum biochemical indices and growth performance of beluga juveniles (11.44 ± 0.56 g).
After 6 weeks of feeding, beluga fed 20 g S. cerevisiae var. ellipsoideus kg −1 showed signifi-
cantly improved final weight, weight gain, SGR and FCR compared to the control treatment.