| To further study the practical function of laminarin polysaccharides in aquatic breeding, laminarin and Epinephelus coioides was selected as the research objects,120 Epinephelus coioides that specifications consistent (90±2.6 g,15±2.25 cm) were randomly and averagely divided into 4 groups. The control group don’t add laminarin polysaccharide,0.5%, and 1.0%,0.5% group add 0.5%,1.0% and 0.5% laminarin respectively. feed for 48 days. Then indexs releted were detected by special methods. The following is the mainly results:1、Effect of Laminaria polysaccharide on the performance, and the activity of related digestive enzyme of Epinephelus coioides:After 48d breeding period, Epinephelus coioides in 0.5% and 1.0% group had an increased daily gain, FAW, WGR and CF (P<0.05), and reduced FCR (P<0.05) compared to grouper offered diets without laminrin supplementation. The HSI on 0.5% group was higher than CK (P<0.05), and FCR was higher than CK significantly (P<0.01); the level of the digestive enzymes in intestinal tract, and Maltase activity on 0.5% group had a significant higher than CK(P<0.01), and the 1.0% group had a higher than CK(P<0.05); the level of Lactase activity in midgut on 1.0% group had a higher than CK (P<0.05); take the control group as contrast, each group each bowel invertase activity is improved, but the difference on those indicators was not significant (P> 0.05).Visible, that feed add 0.5% of laminatin can obviously improve Epinephelus coioides growth performance, and improve the activity of some-related digestive enzymes in gut.2、Effect of laminarin polysaccharides on intestine tissue morphology and mucosal immune barrier of Epinephelus coioides:The result show that:the level of the intestinal length, the width and thickness of the muscle villus were improved in a certain, the nμmber of IELs and MCs were also higher than that in control group; the relative expression level of IL-1β, IL-8 and TLR2 mRNA gene were improved to varying degrees as well, take the control group as a comparison. Among them,there was increased with a significant or significantly(P<0.01 or P<0.05) in 0.5% group and 1.0%group. It follows that laminarin polysaccharide can significantly enhance the intestinal morphology on Epinephelus coioides, raise the level of specific immune cells and immune-related factors, of which 0.5% added contribute to the best results.3、Effects of laminarin on blood parameters of Epinephelus coioides:The level of cytokines (IL-2, IL-6, IFN-a) were higher than that in the control group, the level of total protein and the activity of such enzymes, SOD, LZM and CAT, were also obviously higher compared to the control group. But the level of C3, C4, UREA, CREA and the activity of ALP were lower than that in the control group. There was no marked difference in the levels of ALT and AST in control and treated groups, suggesting that the supplementary feed had no adverse effect on the function of liver or kidney. These results indicate that laminarin can adjust and enhance the immune response of Epinephelus coioides. dose the effect is obvious with 0.5% of polysaccharide added.4、Effects of laminarin on intestinal microflora of Epinephelus coioides:as the experimental results showed, the flora structure within Epinephelus coioides is simple and the dominant microflora species is simple as well. In experimental group, laminarin could significantly enrich diversity of flora structure and increase the popμLationgs of some dominant bacteria in Epinephelus coioides. For instance, its effect was more significant when 0.5% and 1.0% dosage of laminarin were added (the similarity of microflora structure is about 70%),however it’s not obvious when 1.5% dosage added (1st PCR is 82%, second PCR is 80%).Conclusion:take the polysaccharide as functional additives, laminarin can significantly promote the growth of Epinephelus coioides, improve immune function and the structure of gut flora, the effect is most significant when 0.5% of its dosage. |
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