| Three experiments were carried out in the fiberglass of mariculture system in laboratory of Guangdong Ocean University Donghai Island biological base for 8 weeks.The purpose of this study was to investigate the effects of dietary lipid sources,n-3 HUFA and DHA/EPA levels on growth performance,tissue fatty acid and lipid metabolization-related enzyme activities and m RNA expression,immunity and disease resistance of juvenile hybrid grouper(♀ Epinephelus fuscoguttatus × ♂ E.lanceolatus).The results are as follows:1.With white fish meal,soybean meal and wheat gluten meal as the main protein sources,and fish oil(FO),soybean oil(SO),linseed oil(LO),rapeseed oil(RO)and peanut oil(PO)as lipid sources,five kinds of experimental feeds with iso-nitrogenous(crude protein about 49%)and isolipidic(crude lipid about 11%)were formulated and fed grouper(body weight 17.63±0.03 g)for 8 weeks.The results showed that the maximum weight gain rate(WG)of FO group was significantly higher than that of SO,RO and PO groups(P < 0.05),but there was no significant difference between FO and LO groups(P > 0.05).The fatty acid profiles of the liver and muscle reflected that of the five kinds of diet.The activities of superoxide dismutase(SOD),catalase(CAT)and glutathione peroxidase(GSH-Px)in the FO group and were significantly higher than those in the other groups(P < 0.05).The activities of lipase,trypsin and amylase were the highest in the LO group.The activity of fatty acid synthetase(FAS)in FO group was significantly higher than that in the SO,RO and PO groups(P < 0.05),but there was no significant difference between FO and LO groups(P > 0.05).The activity of liver carnitine palmitoyl transferase-1(CPT-1)in the LO group was the highest,which was significantly higher than that in the PO group(P < 0.05),but there was no significant difference from the other groups(P > 0.05).In muscle,the FO group had the highest FAS,CPT-1 and hormone sensitive lipase(HSL)activities,and the lowest glucose-6-phosphate dehydrogenase(G6PD)activity.The m RNA expression of liver CPT-1 and peroxisome proliferator-activated receptor ?(PPAR?)in the SO group was significantly higher than that in the RO and PO groups(P < 0.05),but there was no significant difference with FO group(P > 0.05);The lipoprotein lipase(LPL)m RNA expression in the LO group was significantly higher than that in the other groups(P < 0.05).Apolipoprotein B-100(Apo B-100)m RNA expression in the LO group was the highest,which was significantly higher than that in the RO and PO groups(P < 0.05),but there no significant difference from FO and SO groups(P > 0.05).The expression of CAT m RNA in the liver FO group was significantly higher than that in the SO and RO group(P < 0.05),but no significantly different from that in the LO and PO groups(P > 0.05).Compared with other groups,the m RNA expressions of toll like receptor 3(TLR3),toll like receptor 22(TLR22)and myeloid differentiation factor 88(My D88)in the PO group was significantly increased(P < 0.05);the m RNA expressions of tumor necrosis factor-?(TNF-?)and interleukin-1?(IL-1?)reached the maximum value in the RO group,which was significantly higher than that in the FO group(P < 0.05),but no significantly different from that in the SO and PO groups(P > 0.05).The PO group had the lowest m RNA expression levels of interleukin 10(IL-10)and transforming growth factor ?1(TGF-?1).The m RNA expression level of TGF-?1 in the FO group was significantly higher than that of PO group(P < 0.05),but not significantly different from that of the SO,LO,and PO group(P > 0.05).This experiment showed that compared with the FO group,the LO group had no significant difference the growth performance;the complete replacement of FO by VOs could inhibit the antioxidant capacity of the hybrid grouper;PO could aggravate the inflammatory response.Feed SO and LO increased lipid metabolism capacity by up regulating the liver lipid catabolism genes,and LO and RO groups could improve intestinal digestion and absorption.2.Six isoproteic(about 50% crude protein)and isolipidic(about 11% crude lipid)diets were formulated to contain graded levels of n-3 HUFA(0.65,1.00,1.35,1.70,2.05 and 2.40% of dry matter)by supplementation of fish oil and corn oil and 0.65% group was treated as the control group and fed grouper(body weight 12.06±0.01 g)for 8 weeks.The results showed that with the increasing of the dietary n-3 HUFA levels,the WG first increased and then decreased,and 1.35% group was significantly higher than that in the control group and 2.40% group(P < 0.05).The crude lipid content of 1.00% group was significantly lower than that in the 1.70% and 2.40% groups(P < 0.05),and there was no significant difference with the other groups(P > 0.05).The fatty acid profiles of the liver and muscle reflected that of the diets.Compared with the control group,the serum triglyceride(TG)concentration decreased significantly with the increasing of n-3 HUFA levels(P < 0.05).The serum cholesterol(CHOL)of the 1.35% group was significantly lower than that in the 2.05% group(P < 0.05),but there was no significant difference with the other groups(P > 0.05).Dietary n-3 HUFA levels significantly affected the activity of serum SOD,CAT,GSH-Px,LZM and the content of C3 before challenge(P < 0.05),but had no significant effect on the LZM after challenge(P > 0.05).After challenge,serum CAT,GSH-Px,LZM and C3 all increased sharply compared with that before challenge,while SOD showed the opposite trend.Liver FAS activity of 1.35% group was the lowest,significantly lower than that in the 1.00%,1.70%,and 2.40% groups(P < 0.05),but not significantly different from the control group and 2.05% group(P > 0.05).In muscle,FAS activity decreased with the increasing of dietary n-3 HUFA levels,in which the 2.05% and 2.40% groups were significantly lower than the other groups(P < 0.05).The activities of CPT-1 and HSL reached their maximum values at 2.05% and 1.70%,respectively,which were significantly higher than those in the control group(P < 0.05),but were not significantly different from those in the other groups(P > 0.05).The m RNA expressions of liver CPT-1 in the 2.05% group and Apo B-100 in the 2.40% group were significantly higher than those in the other groups(P < 0.05);liver triglyceride lipase(ATGL)in the 2.40% group was significantly higher than that of the 1.35% and 1.70% groups(P < 0.05).With the increasing of dietary n-3 HUFA levels,liver FAS,acetyl-Co A carboxylase alpha(ACC?),and peroxisome proliferators-activated receptor ?(PPAR?)m RNA expressions significantly decreased(P < 0.05).In muscle,with the increasing of dietary n-3 HUFA levels,the expression levels of CPT-1,ATGL and PPAR? m RNA increased first and then decreased,reaching the maximum values in the 1.70% and 1.35% groups,respectively.Before challenge,the expression levels of intestinal TLR22 and My D88 m RNA in the 2.40% group were significantly increased,and the expression levels of TNF-? and IL-1? in the 2.05% group were significantly higher than those in the 1.00% and 1.35% groups(P < 0.05).In addition,the expression levels of kidney TLR22 and IL-1? in the 1.70% group were significantly lower than those in the control group(P < 0.05).After challenge,the expression level of intestinal My D88 m RNA in the 1.35% group was significantly higher than that in 1.00% and 1.70%-2.40% groups,and the minimum expression levels of TNF-? and IL-1? in the 1.70% group.The expression level of kidney IL-10 in the 1.70% group was significantly higher than that in other groups,while the expression level of IL-10 showed a opposite trend,which was significantly lower than that in the 2.40% group(P < 0.05).The activities of intestinal lipase and trypsin reached the maximum value in the 2.05% group.With the increase of n-3 HUFA levels,the intestines of OTUs decreased significantly(P < 0.05).On the phyla levels,Proteobacteria,Bacteroidetes and Firmicutes were detected as the dominant phyla in the intestine.The n-3 HUFA supplementation resulted in increased abundance of Bacteroidales＿S24-7＿group and Lachnospiraceae.The results showed that the moderate n-3 HUFA(1.47%-1.70%)could significantly improve the growth performance,disease resistance and inflammation inhibition ability,promote the catabolism of liver and muscle,inhibit the anabolism and reduce the abnormal deposition of lipid in hybrid grouper.The increase of dietary n-3 HUFA level can improve the abundance of intestinal probiotics,and 1.00% and 1.35% groups significantly promoted the structural integrity of proximal intestine in hybrid grouper.3.Five isoproteic(about 48% crude protein)and isolipidic(about 12% crude lipid)diets were formulated to containing differential ratios of DHA/EPA(0.65,1.00,1.35,1.70,2.05 and 2.40%)by supplementation of DHA purified oil and EPA purified oil and 0.77 group was treated as the control group and fed grouper(body weight 9.87±0.02 g)for 8 weeks.The results showed that with the increasing of dietary DHA/EPA ratios,WG and SGR increased first and then decreased,and in the 1.31 group were significantly higher than those in control group and 4.10 group(P < 0.05),but there was no significant difference with the other groups(P > 0.05).With the increasing of DHA/EPA ratios,serum TG content decreased significantly,and the high density lipoprotein(HDL-C)increased significantly(P < 0.05).The serum alanine aminotransferase(ALT)and aspartate aminotransferase(AST)in the 1.31 group were the lowest,which were significantly lower than those of 4.10 group(P < 0.05).The activities of serum SOD,CAT and GSH-Px in the 2.44 group were significantly higher than those in the 0.77 and 1.31 groups(P < 0.05).The activity of LZM,alkaline phosphatase(AKP)and the content of immunoglobulin(Ig M)decreased with the increasing of DHA/EPA ratios,reaching the maximum value in the 2.44 and 3.20 groups respectively and significantly higher than that in the control group(P < 0.05).The liver CPT-1 and G6 PD activities in the 3.20 and 4.10 groups were significantly higher than those in the 0.77 and 1.31 groups(P < 0.05).The muscle CPT-1 and LPL activities in the 2.44 and 3.20 groups were significantly higher than those in the 0.77 and 1.31 groups(P < 0.05).The liver CPT-1 and PPAR? m RNA expression in the 2.44 group was the highest,which was significantly higher than that in the control group(P < 0.05);the expression of FAS m RNA in 3.20 group was the lowest,significantly lower than that in the control group and 1.31 group;the expression of ACC? m RNA in the control group was significantly higher than that in the other groups(P < 0.05).The muscle CPT-1 m RNA expression in the 2.44 group was the highest,which was significantly higher than that in the control group(P < 0.05),while the expression of 6GPD m RNA in the 1.31 group was significantly lower than that in the 4.10 group(P < 0.05).The results showed that when the dietary ratio of DHA/EPA was 2.12,the juveniles hybrid grouper had the best WG,and the appropriate ratios of DHA/EPA(1.31-3.20)could significantly improve the antioxidant capacity and reduce the excessive lipid deposition. |
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