| In this thesis,the main grouper culture species in China,juvenile hybrid grouper(Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂),to investigate the effects of three plant protein replacements to fish meal,Peanut Cake(PNK),Corn Distillers Dried Grains with Solubles(DDGS)and Corn Gluten Meal(CGM),on growth,immunity and intestinal health for juvenile hybrid grouper.1.The diets were formulated with 45% fishmeal content as the control group(P0)and 7 iso-nitrogenous and iso-lipidic diets were formulated using PNK to replace 11%,22%,33%,44%,55%and 66%(P1,P2,P3,P4,P5,and P6)of fishmeal protein,respectively.A total of 840 juvenile hybrid grouper with uniform body weight(13.20 ±0.05 g)were selected from 7 treatments and 4 replicates(30 fish each)were farmed for eight weeks.The results showed that the weight gain rate(WGR)of the P4,P5,and P6 groups were significantly lower than the other groups(P<0.05),however,the feed conversion rate(FCR)and specific growth rate(SGR)were significantly higher than the other groups(P<0.05).The whole fish moisture content in the P0 group and the ether extract(EE)content in the P4 group were significantly higher(P<0.05)than in the other groups(P< 0.05),and the crude protein(CP)content in the P6 group was the lowest and significantly lower than that the P0 group(P<0.05).Total protein(TP)showed a trend of decreasing and then increasing,total cholesterol(TC)showed a trend of gradually decreasing and was significantly higher in the P0 and P1 groups than in the other groups(P<0.05),glutathione transaminase(AST)activity and total antioxidant(T-AOC)capacity were significantly higher in the P6 group than in the other groups(P<0.05),and malondialdehyde(MDA)contents was significantly lower in the P4 group than in the other groups(P<0.05).The trypsin(TPS)activity was significantly higher in the P4,P5,and P6 groups than in the P0 and P1 groups(P<0.05),while the lipase(LPS)activity was significantly lower in the P5 and P6 groups than in the other groups(P<0.05).Oil-red stained sections of the liver showed that fat deposition gradually increased with increasing levels of PNK substitution in the diet.The results showed that the core microflora at the phylum level were Proteobacteria and Firmicutes;at the genus level,the harmful bacteria Photobacterium were significantly higher in the P4 group than in the other groups(P<0.05).The optimum replacement level of PNK in the feed was 21.94%,using WGR as the basis for judgment.2.The diets were formulated with 45% fishmeal content as the control group(D0)and 6 iso-nitrogenous and iso-lipidic diets were formulated using DDGS to replace6.67%,13.33%,20%,26.67%,and 33.33%(D1,D2,D3,D4,and D5)of fishmeal protein,respectively.A total of 720 juvenile hybrid grouper with uniform body weight(11.88 ± 0.05 g)were selected from 6 treatments and 4 replicates(30 fish each)were farmed for eight weeks.The results showed that there was no significant effect of DDGS substitution for FM on SR and FCR(P>0.05),but WGR and SGR of D0,D1,and D2 groups were significantly higher than the other groups(P<0.05).There was no significant difference in serum TG content and ALT activity(P>0.05),and MDA content showed a gradual decrease,with the D4 and D5 groups being significantly lower than the remaining groups(P<0.05).With the increase in substitution level,the amylase(AMS)activity in the intestine decreased significantly and was significantly lower in the D3 and D4 groups than in the other groups(P<0.05),while LPS activity reached a maximum in the D3 group,which was significantly higher than the other groups(P<0.05).With increasing substitution levels,the cupped cells gradually decreased,and the microvilli in the D4 and D5 groups were severely damaged and had significantly lower intestinal villi height(VH)than in the other groups(P<0.05),while there was no significant difference in villi width(VW)and muscle thickness(MT)(P>0.05).The m RNA levels of anti-inflammatory factors il-10 and tgf-β1 tended to decrease with increasing substitution levels,and the m RNA levels of pro-inflammatory factors tnf-α and il-1β tended to increase with increasing substitution levels.The Ace and Chao indices were significantly higher in the D0 group than in the D5 group(P<0.05),however,there were no simpson and shannon groups between the groups However,there was no significant difference between simpson and shannon groups(P>0.05).The optimal replacement level of DDGS in the feed was 6.11%,using SGR as the basis for judgment.3.The diets were formulated with 45% fishmeal content as the control group(C0)and 6 iso-nitrogenous and iso-lipidic diets were formulated using CGM to replace 11%,22%,33%,44%,and 55%(C1,C2,C3,C4,and C5)of fishmeal protein,respectively.A total of 540 juvenile hybrid grouper with uniform body weight(11.88 ± 0.05 g)were selected from 6 treatments and 3 replicates(30 fish each)were farmed for eight weeks.The results showed that WGR and SR were significantly lower in C4 and C5 groups than in C0,C1,and C 2 groups(P<0.05),SGR was significantly lower in the C5 group than in C0,C1,and C2 groups(P<0.05),and FCR was not significantly different between groups(P>0.05).Serum T-AOC capacity was significantly higher in the C3 group than in the other groups(P<0.05),the MDA content was significantly higher in groups C0,C1,and C2(P<0.05),and complement C4 was significantly lower in group C0 than in groups C3 and C4(P<0.05).TPS activity was significantly lower than the rest of the groups(P<0.05),LPS activity was significantly lower in C0 and C1 groups(P<0.05),AMS activity was significantly higher in the C3 group(P<0.05),VH was significantly higher in C0 group(P<0.05),MT was significantly higher in C0 and C1 groups than C3 and C5groups(P<0.05).The m RNA levels of intestinal epinecidin genes increased and then decreased with increasing substitution levels,and were significantly higher in the C2 group than in the C0 group(P<0.05).The m RNA levels of anti-inflammatory genes il-10 and tgf-β1 both decreased and then increased with the increase of substitution level,and the m RNA levels of pro-inflammatory genes tnf-α and il-1β both increased and then decreased with the increase of substitution level.The optimal substitution level of CGM in feed was 9.35%,using WGR as the basis for judgment. |
