In recent years, aquaculture research has focused on probiotics, prebiotics, and β-glucans, in order to improve health status and growth performance. Information regarding the effects of β-glucan on growth performance and intestinal immunity of mirror carp (Cyprinus carpio L.) is scarce. An experiment was therefore conducted to investigate the effects of a yeast β-glucan preparation (MacroGard(®) ) on growth performance, intestinal morphology and haemato-immunological indices of mirror carp. Carp (initial weight 11.1 ± 0.0 g) were fed highly purified diets supplemented with 0% (control), 0.1%, 1% or 2% MacroGard(®) for 8 weeks. Fish fed diets containing 1% and 2% MacroGard(®) showed significant improvements in weight gain, specific growth rate and feed conversion ratio compared to fish fed both the control and the 0.1% MacroGard(®) containing diet. Histological appraisal of the intestine showed a significantly higher infiltration of leucocytes into the epithelial layer of fish fed diets supplemented with 1% and 2% MacroGard(®) in the anterior intestine compared to fish fed the control and 0.1% MacroGard(®) diet. This effect was not observed in the posterior intestine. There were no significant differences in the intestinal absorptive surface area and number of goblet cells in either intestinal region. At the end of the experiment, the haematological status of the fish was examined. Compared to control fed fish, the haematocrit value was significantly elevated in fish fed the 2% MacroGard(®) diet. Furthermore, the blood monocyte fraction was significantly higher in fish fed the 1% and 2% MacroGard(®) diets. No significant changes were observed in the other blood parameters assessed. The present study shows that high dietary β-glucan inclusion increases growth performance without detrimental effects on the health indicators assessed. Increased intraepithelial leucocytes in the anterior intestine may indicate a localized immune response; no detrimental effects on intestinal morphology were observed.

The e¡ect of diets supplemented with varied levels of inorganic phosphorus (P) (NaH 2 PO 4 ) on the growth, body composition, nutrient digestibility and mineralization in common carp (Cyprinus carpio L) was evaluated to determine the optimum P requirements. The six diets used were DPO, as the basal diet with a total P content of1.30 g kg À 1 , and DP1, DP2, DP3, DP4 and DP5, which contained 4.10, 6.70, 11.6, 14.9 and 23.4 g P kg À 1 respectively. Weight gain, SGR, apparent digestibility coe⁄cient of organic matter and P, whole body ash, P, Ca and Mg increased signi¢cantly with increasing dietary P levels while dry matter (DM), fat and Zn content decreased. Feed conversion ratio was the poorest (Po0.05) in ¢sh fed DPO, suggesting P de¢ciency. The apparent digestibility coe⁄cient of P was 18% in the DPO-fed group, which increased from 69% in DP1 to 92% in DP5 after P supplementation, revealing lower digestibility of the native P than that in NaH 2 PO 4 . Broken-line analyses based on weight gain, P content of ¢sh bones and whole body against total dietary and digestible P (data in brackets) contents showed the optimum P requirement for the growth of common carp to be 6.87 (5.55) g kg À 1 DM, and the requirement for optimum mineralization in bones and whole body to be 9.10 (7.62) and 14.7 (13.2) g kg À 1 . Ã kg À 1 diet: vitamin A, 8050 IU; vitamin D3, 800 IU; vitamin E, 150.5 mg; vitamin K3, 5.90 mg; vitamin C, 268.3 mg; thiamin HCl, 19.6 mg; ribo£avin 30.8 mg; pyridoxine HCl, 14.7 mg; vitamin B 12 0.10 mg; Ca-D-pantothenate, 56.0 mg; nicotinic acid, 100.1mg; folic acid, 6.20 mg; inositol, 199.5 mg; biotin, 0.50 mg mixed with maize starch. mg. DPO, diet without supplemental P; DP1, diet supplemented with 2.5 g P kg À 1 ; DP2, diet supplemented with 5 g P kg À 1 ; DP3, diet supplemented with 10 g P g À 1 ; DP4, diet supplemented with 15 g P kg À 1 ; DP5, diet supplemented with 20 g P kg À 1 .Phosphorus for carp growth and mineralization L C Nwanna et al.Means on a row followed by similar superscripts are not di¡erent (P40.05). DPO, diet without supplemental P; DP1, diet supplemented with 2.5 g P kg À 1 ; DP2, diet supplemented with 5 g P kg À 1 ; DP3, diet supplemented with 10 g P g À 1 ; DP4, diet supplemented with 15 g P kg À 1 ; DP5, diet supplemented with 20 g P kg À 1 .Aquaculture Research, 2010, 41, 401^410 Phosphorus for carp growth and mineralization L C Nwanna et al.

-fed fish compared with the control-fed fish. Overall, sequence analysis detected microbiota belonging to the phyla Proteobacteria, Firmicutes, Fusobacteria and unidentified uncultured bacteria. DGGE analyses also revealed that dietary MacroGard â reduced the number of observed taxonomical units (OTUs) and the species richness of the allochthonous microbiota after 2 weeks, but not after 4 weeks. In contrast, dietary MacroGard â reduced the number of OTUs, the species richness and diversity of the autochthonous microbiota after 2 weeks, and those parameters remained reduced after 4 weeks. Transmission electron microscopy revealed that intestinal microvilli length and density were significantly increased after 4 weeks in fish fed diets supplemented with 1% MacroGard â . Conclusions: This study indicates that dietary MacroGardâ supplementation modulates intestinal microbial communities of mirror carp and influences the morphology of the apical brush border. Significance and Impact of the Study: To the authors' knowledge, this is the first study to investigate the effects of b-(1,3)(1,6)-D-glucans on fish gut microbial communities, using culture-independent methods, and the ultrastructure of the apical brush border of the enterocytes in fish. This prebiotic-type effect may help to explain the mechanisms in which b-glucans provide benefits when fed to fish.

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