| In this study,the triploid rainbow trout(initial fish weight 232±0.44g)cultured by Qinghai Minze Longyangxia Ecological Aquaculture Co.,Ltd.was used as the research object,and the lipid levels were 6.6%,12.3%,14.8%.Nitrogen feeds such as 19.5%,22.8%,and 29.4% of the six experiments were cultured for 84 days.By measuring the growth performance of triploid rainbow trout,the expression of growth-related genes in the liver,antioxidant capacity,blood biochemical parameters,digestive enzyme activity,intestinal tissue morphology,expression of lipid synthesis and transport related genes in the liver(m RNA levels),muscle nutrients,muscle texture and flesh color and other indicators to determine the appropriate dietary lipid level,analysis of dietary lipid levels on tripod rainbow trout growth health and fat metabolism and meat quality,provide a theoretical basis for triploid rainbow trout breeding.The main results include the following three aspects:1.The effects of dietary lipid levels on the growth and health of triploid rainbow trout.Growth: The final body weight and specific growth rate of triploid rainbow trout reached a maximum at a feed fat level of 29.4%.The feed coefficient remained low after falling to a minimum when the feed fat level was 22.8%.A second-order regression equation for specific growth rates and feed fat levels indicated that when the feed protein level was 46%,the optimal fat requirement was 27.2%.The expression levels of growth hormone receptor(GHR),insulin-like growth factor(IGF-I,IGF-II)in the liver were significantly higher in the fat-feed group(22.8%,29.4%)than in the low-fat diet group(6.6%,14.8%),the expression level of IGF-II decreased when the feed fat level was 29.4%.Health: With the increase of feed fat level,the malondialdehyde(MDA)content and total antioxidant capacity(T-AOC)in the liver did not change significantly(P>0.05),and the MDA content in plasma increased significantly,T-AOC is significantly lower.The MDA content in the intestine decreased,and T-AOC did not change significantly.There were no significant differences in alanine aminotransferase,aspartate aminotransferase,alkaline phosphatase and lactate dehydrogenase in the blood(P>0.05).2.The effects of dietary lipid levels on the digestive and metabolic capacity of triploid rainbow trout.Digestive enzymes: As the feed fat level increased,the intestinal protease activity did not change significantly(P>0.05),while the lipase activity increased to a maximum when the feed fat level was 19.5%,and then remained at a high level,amylase Activity continues to increase with feed fat levels.The protease activity of the pylorus increased until the feed fat level reached 22.8%,then reached the maximum and then decreased,and the lipase activity gradually increased to a maximum when the feed fat level was 29.4%.As the dietary lipid levels increased,the pepsin activity increased to a maximum when the dietary lipid level was 22.8% and remained high.In terms of intestinal tissue morphology: with the increase of dietary lipid levels,there was no significant difference in intestinal villus height,microvilli height and epithelial cell thickness(P>0.05);both goblet cell number and basement membrane thickness were related to feed fat level.The rise is rising.Fat metabolism: m RNA levels of liver acetyl-Co A carboxylase(ACC)and fatty acid synthase(FAS)in the high-fat diet group(22.8%,29.4%)and the low-fat diet group(6.6%,14.8%)The change was not significant(P>0.05),while the expression level of ATP-citrate lyase(ACLY)decreased first and then remained low with the increase of feed fat level.The expression levels of lipoprotein lipase(LPL),fatty acid transporter-1(FATP-1)and fatty acid translocase(CD36)in the liver were significantly higher in the fat group than in the low fat group(P<0.05).In terms of fat deposition: with the increase of feed fat level,there was no significant change in the deposition of liver fat in triploid rainbow trout(P>0.05),and the fat deposition of whole fish and muscle continued to increase,reaching at the highest feed fat level.Maximum;visceral fat deposition remained high after 19.4% reached its maximum.3.The effects of dietary lipid levels on the quality of triploid rainbow trout.Nutritional ingredients: As the lipid level of the feed increased,the water content of the triploid rainbow trout was gradually reduced;the ash content decreased first and then increased,and reached the lowest at 19.5% lipid level;there was no significant difference in crude protein(P>0.05);As the level of feed fat increases,it continues to rise.The moisture content in the muscle continued to decrease with the increase of the dietary lipid level;there was no significant difference in the ash content(P>0.05);the crude protein content increased first and then decreased at the feed fat level of 19.5% to reach the maximum;The content increased continuously with the increase of dietary lipid levels,and the lowest level of fatty acid was significantly lower than that of other fat groups(P<0.05).The content of n-3 unsaturated fatty acid was higher in the fat diet group.Muscle quality: muscle hardness was higher in the fat group than in the low fat group.The p H value and the red color value of the fish meat all increased.In conclusion,under the conditions of this study,the specific growth rate of triploid rainbow trout continued to increase with the increase of dietary lipid level.When the feed protein level was 46%,the optimal fat requirement was 27.2%;high dietary lipid level It has little effect on the antioxidant capacity of the intestines and liver;as the dietary lipid levels increases,the digestive capacity and fat transport capacity of triploid rainbow trout increases;the fat content of whole fish and muscle increases,the p H of the muscle,The red value of the flesh color has an increasing trend. |
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