Conjugated linoleic acid in diets for large-size rainbow trout (Oncorhynchus mykiss): effects on growth, chemical composition and sensory attributes

Conjugated linoleic acid alters growth performance, tissue lipid deposition, and fatty acid composition of darkbarbel catfish (Pelteobagrus vachelli)

Fatty liver syndrome is a prevalent problem of farmed fish. Conjugated linoleic acid (CLA) has received increased attention recently as a fat-reducing fatty acid to control fat deposition in mammals. Therefore, the aim of the present study was to determine whether dietary CLA can reduce tissue lipid content of darkbarbel catfish (Pelteobagrus vachelli) and whether decreased lipid content is partially due to alterations in lipid metabolism enzyme activities and fatty acid profiles. A 76-day feeding trial was conducted to investigate the effect of dietary CLA on the growth, tissue lipid deposition, and fatty acid composition of darkbarbel catfish. Five diets containing 0 % (control), 0.5 % (CLA0.5), 1 % (CLA1), 2 % (CLA2), and 3 % (CLA3) CLA levels were evaluated. Results showed that fish fed with 2-3 % CLA diets showed a significantly lower specific growth rate and feed conversion efficiency than those fed with the control diet. Dietary CLA decreased the lipid contents in the liver and intraperitoneal fat with the CLA levels from 1 to 3 %. Fish fed with 2-3 % CLA diets showed significantly higher lipoprotein lipase and hepatic triacylglycerol lipase activities in liver than those of fish fed with the control, and fish fed with 1-3 % CLA diets had significantly higher pancreatic triacylglycerol lipase activities in liver than those of fish fed with the control. Dietary CLA was incorporated into liver, intraperitoneal fat, and muscle lipids, with higher percentages observed in liver compared with other tissues. Liver CLA deposition was at the expense of monounsaturated fatty acids (MUFA). In contrast, CLA deposition appeared to be primarily at the expense of MUFA and n-3 polyunsaturated fatty acids (PUFA) in the intraperitoneal fat, whereas in muscle it was at the expense of n-3 PUFA. Our results suggested that CLA at a 1 % dose can reduce liver lipid content without eliciting any negative effect on growth rate in darkbarbel catfish. This lipid-lowering effect could be in part due to an increment in the activity of lipid metabolism enzymes and an extensive interconversion of fatty acids. Although CLA deposition in muscle (0.66-3.19 % of total fatty acids) are higher than presented in natural sources of CLA, EPA (C20:5n-3) in fish muscle appears simultaneously expendable, when the fish fed with 2-3 % CLA.

Effects of conjugated linoleic acid on growth, non-specific immunity, antioxidant capacity, lipid deposition and related gene expression in juvenile large yellow croaker (Larmichthys crocea) fed soyabean oil-based diets

The effects of conjugated linoleic acid (CLA) on growth performance, non-specific immunity, antioxidant capacity, lipid deposition and related gene expression were investigated in the large yellow croaker (Larmichthys crocea). Fish (7·56 (sem 0·60) g) were fed soyabean oil-based diets with graded levels of CLA (0, 0·42, 0·83, 1·70 %) for 70 d. Quantitative PCR was used to assess the effects of CLA on the transcription of inflammation- and fatty acid oxidation-related genes. Growth in fish fed the diet with 0·42 % CLA was significantly higher. Also, phagocytic index and respiratory burst activity were significantly higher in fish fed the diets containing 0·42 and 0·83 % CLA, respectively. Hepatic total antioxidative capacity and catalase activities increased significantly when CLA increased from 0 to 0·83 %, and then decreased with further increase of CLA. However, hepatic malondialdehyde content decreased significantly as dietary CLA increased. Lipid concentration in the whole body and muscle increased significantly with increasing dietary CLA. Transcription of genes related to inflammation (cyclo-oxygenase-2 and IL-β) in the liver and kidney and fatty acid oxidation (carnitine palmitoyl transferase I and acyl CoA oxidase) in the kidney decreased significantly as dietary CLA increased. PPARα and acyl CoA oxidase expression in the liver decreased significantly as CLA increased from 0·42 to 1·70 %. These results strongly suggest that dietary CLA could significantly affect growth performance, non-specific immunity, antioxidant capacity, lipid deposition and transcription of inflammation- and fatty acid oxidation-related genes of the large yellow croaker. This may contribute to our understanding of the mechanisms related to the physiological effects of dietary CLA in fish.

Influence of dietary conjugated linoleic acid on growth, fatty acid composition and hepatic lipogenesis in large yellow croaker (Pseudosciaena crocea R.)

We examined the effects of conjugated linoleic acid (CLA) on growth, fatty acid composition and enzyme activity of fatty acid oxidation in the liver of large yellow croaker. We divided 1600 fish (average initial weight 150 g) into 4 groups and reared them in 8 cages. Four dietary treatments were formulated to contain 0%, 1%, 2% and 4% (w/w) CLA, respectively. The fish were fed for 10 weeks ad libitum twice daily. We found that the dietary CLA had no effect on growth, biometric parameters and whole body proximate (P>0.05), but showed some significant effects on the fatty acid composition in both muscle and the liver. The activities of lipogenic enzymes were slightly depressed in fish fed with increasing levels of CLA when compared with control (P>0.05). Dietary CLA supplementation had no effects on liver lipid content, but significantly increased the contents of saturated fatty acids (SFA) and polyunsaturated fatty acids (PUFA) (P<0.05) and decreased monounsaturated fatty acid (MUFA) content in both muscle and the liver. Dietary CLA inclusion resulted in significant increases of the biologically active cis-9, trans-11 and trans-10, cis-12 isomers in both tissues (P<0.05). The total accumulation of CLA was higher in the liver (3.83%, w/w) than in muscle (3.77%, w/w) when fed with 4% (w/w) CLA. This study demonstrates that large yellow croakers are capable of absorbing and depositing CLA and long-chain n-3 PUFA in the liver and muscle, showing that this species fed with CLA could be an important human food source for these healthful fatty acids.

Board-invited review: the biology and regulation of preadipocytes and adipocytes in meat animals

The quality and value of the carcass in domestic meat animals are reflected in its protein and fat content. Preadipocytes and adipocytes are important in establishing the overall fatness of a carcass, as well as being the main contributors to the marbling component needed for consumer preference of meat products. Although some fat accumulation is essential, any excess fat that is deposited into adipose depots other than the marbling fraction is energetically unfavorable and reduces efficiency of production. Hence, this review is focused on current knowledge about the biology and regulation of the important cells of adipose tissue: preadipocytes and adipocytes.