| The aim of this study was to determine the optimal requirement for inositol in juvenile hybrid sturgeon(Acipenser baerii ? × A.schrenckii ?)and the effects of inositol in feed on apparent digestibility of nutrients and intestinal microflora in juvenile hybrid sturgeon.Feeds were prepared when casein,gelatin,fish meal and soybean meal were the sources of feed protein,dextrin was the sugar source,the lipid sources were fish oil and soybean oil,and the inositol levels in the feeds were 0,200,400,800,1600 and 3200 mg/kg,respectively.The inositol levels detected actually in the feeds were70.2,130.0,270.2,443.0,1096.6 and 1997.3 mg/kg,respectively.There were 6experimental groups,with 3 replicates in each group and 15 juvenile hybrid sturgeons in each replicate.The juvenile hybrid sturgeons with an initial mean weight of 28.28 ±0.41 g were fed with apparent satiation for 12 weeks,at water temperature of18.2?-20.6?.The results are as follows:1.Dietary inositol requirement of juvenile hybrid sturgeonThe purpose of this study was to explore the optimal nutrient requirement for inositol in juvenile hybrid sturgeon by evaluating its growth performance and liver inositol accumulation.The results showed that:(1)With the increase of inositol in the feed from 0 mg/kg to 400 mg/kg,the weight gain(WG)also increased from(903.7 ±25.6)g to(996.1 ± 55.6)g(p < 0.05),but with the increase of inositol from 800 mg/kg to 3200 mg/kg,there was no significant difference in WG(p > 0.05),which were(1017.9 ± 18.2)g,(1040.9 ± 32.7)g and(1029.8 ± 58.9)g,respectively.Specific growth rate(SGR)showed a similar trend.The feed conversion ratio(FCR)and survival rate(SR)were not affected by dietary inositol supplementation(p > 0.05).(2)Dietary inositol did not affect whole-body and muscle crude protein and ash contents(p > 0.05),while dietary inositol significantly affected the muscle and whole-body crude lipid and moisture contents(p < 0.05).(3)When 1600 mg/kg inositol was added into the feed,the serum triglyceride(TG)of juvenile hybrid sturgeon was the lowest(6.8mmol/L).When the added amount of AST was 800 mg/kg,its level was significantly lower than that of other groups,which was 387.4 U/L.ALT first decreased and then increased with the inositol level,and the lowest levels,80.7 and 83.2 U/L,were obtained at 800 mg/kg and 1600 mg/kg,respectively.(4)Liver inositol accumulation increased significantly with the increase of inositol in feed from 0 mg/kg to 800 mg/kg(p<0.05),but leveled off after 1600 mg/kg(p>0.05).In summary,the growth performance and liver inositol accumulation were taken as the comprehensive evaluation indexes,and this study indicated that the optimal dietary inositol requirement for juvenile hybrid sturgeon(Acipenser baerii?×A.schrenckii?)was 335.84 mg/kg and 590.65 mg/kg based on the maximum WG and liver inositol accumulation indices,respectively.2.Effects of dietary inositol on nutrient apparent digestibility and antioxidant properties of juvenile hybrid sturgeonThe purpose of this study was to investigate the effects of dietary inositol on the apparent digestibility of dry matter,crude protein,crude lipid and amino acid and antioxidant properties in juvenile hybrid sturgeon.The results showed:(1)The apparent digestibility of dry matter in 400(57.18 ± 0.29%),800(56.43 ± 0.80%),1600(52.19 ±0.97%)and 3200(54.09 ± 1.01%)mg/kg groups were significantly higher than that of 0(49.46 ± 0.93%)and 200(48.16 ± 1.43%)mg/kg groups(p < 0.05).(2)The apparent digestibility of crude lipid in 200,400 and 800 mg/kg supplement inositol groups were significantly higher than that of 0,1600 and 3200 mg/kg supplement inositol groups(p< 0.05).The apparent digestibility of crude lipid was lowest in 3200 mg/kg groups,and significantly lower than other supplement inositol groups(p < 0.05).(3)The apparent digestibility of crude protein in all groups were not significantly affected by the dietary inositol(p > 0.05).(4)The apparent digestibility of total amino acids in 3200(78.18 ±10.55%)mg/kg supplement inositol groups was significantly lower than other supplement inositol groups(p < 0.05).(5)The addition of inositol in the feed had no significant effect on the catalase(CAT)activity in the liver of juvenile hybrid sturgeon(p > 0.05),but the addition of 400,800 and 1600 mg/kg inositol in the feed significantly increased the total antioxidant capacity(T-AOC)activity in the liver of juvenile hybrid sturgeon(p > 0.05).Malondialdehyde(MDA)level also increased with the increase of inositol.The activity of superoxide dismutase(SOD)was the highest when 0 and 3200mg/kg inositol were added(p < 0.05).The results indicated that suitable dietary inositol(400 ? 800 mg/kg)could improve the apparent digestibility of dry matter,crude lipid,crude protein and total amino acids of juvenile hybrid sturgeon(Acipenser baerii?×A.schrenckii?).3.Effects of adding inositol in feed on microflora in the intestinal tract of juvenile hybrid sturgeonIn order to determine the effects of inositol on the microbial community in the intestinal tract of juvenile hybrid sturgeon,this experiment explored the effect of adding different levels of inositol in feed on the composition,Alpha and Beta diversity of the microbial community in the intestinal tract of juvenile hybrid sturgeon through high-throughput sequencing technology.The results showed that :(1)The contents of the hind intestine of juvenile hybrid sturgeon was sequenced by high-throughput 16 s r RNA v3-v4 region amplinos,and a total of 3339801 Raw reads and 3194976 Clean reads were obtained,with an average length of about 400 bp for each sample.After species annotation and homogenization were done,a total of 1381 OTUs were obtained,of which 131 were total OTUs,and the number of unique OTUs gradually decreased from 0 to 3200 with the increase of inositol in the feed.(2)The addition of inositol in the feed changed the dominant bacteria group of the intestinal microorganisms of the juvenile hybrid sturgeon.With the addition of inositol in the feed,the dominant bacteria group changed from Proteobacteria to Fusobacteria and Firmicutes,and in each group,except Proteobacteria,the dominant bacteria in the 0 mg/kg addition group,were all Fusobacteria.(3)The addition of inositol in feed had no effect on the Simpson index of the Alpha diversity of microflora in the intestinal tract of juvenile hybrid sturgeon,but had significant effect on shannon index,chao1 index and ACE index.The Alpha diversity of intestinal microflora changed with the addition of inositol in the feed,and the shannon index decreased with the addition of inositol in the feed.The 0 mg/kg addition group was significantly higher than the other addition groups,and there was no significant difference among them.Chao1 and ACE indices are the largest in the 200mg/kg addition group and the smallest in the 3200 mg/kg addition group.(4)The addition of inositol in feed significantly affected the Beta diversity of microflora in the intestinal tract of juvenile hybrid sturgeon.The results of PCo A analysis showed that inositol in the feed made the microbial community structure of the intestinal tract of juvenile hybrid sturgeon show a high degree of similarity between each group and close relationship,and inositol has a significant effect on them.The results of PCA analysis showed that 0 mg/kg was the most distant in the PCA plot,and the other groups showed a high degree of aggregation.In summary,the addition of inositol in the feed had an effect on the composition of microflora,Alpha diversity and Beta diversity in the intestinal tract of juvenile hybrid sturgeon.The addition of inositol in the feed changed the dominant flora of intestinal tract and made the microbial flora of intestinal tract have higher richness and diversity. |
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