Abstract
The effects of dietary conjugated linoleic acid (CLA) on lipid concentrations and fatty acid composition of various tissues were studied in young chicks. From 7 days of age, a total of 160 chicks were divided into 4 groups, placed into 4 pens per group (10 birds per pen) and fed one of four experimental diets containing 6% tallow (TO 6%), 4% tallow plus 2% CLA (TO 4%-CLA 2%), 2% tallow plus 4% CLA (TO 2%-CLA 4%) or 6% CLA (CLA 6%) for 3 weeks. There were no significant differences in growth performances and the relative weights of various organs, but relative liver weight of chicks fed dietary CLA at 4 and 6% levels was significantly higher (p<0.05) than that of TO 6% group. The chemical compositions of leg muscle were not affected by CLA feeding. However, hepatic total lipid of chicks fed 6% CLA diet was significantly higher (p<0.05) than those of TO 6% and TO 4%-CLA 2% groups. The concentrations of various lipid fractions in serum were not affected by CLA feeding. With the increase in dietary CLA levels, cis 9-trans 11 CLA, trans 10-cis 12 CLA and total CLA of leg muscle increased linearly. The relative proportions of C18:1 ω-9 and C20:4 ω-6 fatty acids in the leg muscles of chicks fed the CLA containing diets were significantly lower (p<0.05) than those of TO 6% group. These results indicate that the levels of CLA isomers were increased linearly in dose-dependent manner after feeding of synthetic CLA source. But it was also observed that excessive amount of dietary CLA resulted in the possible adversely effects, such as increase of liver weight, hepatic lipid accumulation and serum GOT level.
Highlights
Conjugated dienoic derivatives of linoleic acid (CLA)are a series of positional and geometric isomers of linoleic acid
These results indicate that the levels of CLA isomers were increased linearly in dose-dependent manner after feeding of synthetic CLA source
CLA has been suggested by some animal studies to possess potent antiatherogenic effects (Lee et al, 1994; Nicolosi et al, 1997)
Summary
Are a series of positional and geometric isomers of linoleic acid. Results of several studies show that dietary CLA isomers have an anticarcinogenic effect and modulate immune response in experimental animals (Ip et al, 1999; Yamasaki et al, 2000). Cook et al (1993) showed that CLA improved immune responses in rat and prevented the catabolic effects following immune stimulation in chicks. Results of several studies show that dietary CLA isomers have an anticarcinogenic effect and modulate immune response in experimental animals (Ip et al, 1999; Yamasaki et al, 2000). Aydin et al (2001) reported that CLA feeding resulted in embryonic mortality by causing the transformation of fatty acid in the egg yolk. Du and Ahn (2002) found that the hardness of breast muscle from chickens fed CLA containing diets was increased, and this was associated with the change of fatty acid profiles in muscle lipid. The objectives of the present study were to investigate the dietary effects of CLA on the lipid concentrations and fatty acid composition in various tissues of young chicks.
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