Abstract
The aim of the investigation was to study the effect of dietary conjugated linoleic acid (CLA) on the concentrations of lipids, fatty acids and iodothyronines: thyroxine (T 4 ), triiodothyronine (T 3 ), reverse-triiodothyronine (rT 3 ), free T 4 (FT 4 ) and free T 3 (FT 3 ) in blood plasma of pigs. The experiment was carried out on 50 fatteners (average liveweight 50 kg) divided into 5 groups (5 gilts and 5 barrows per group). The pigs were fed a basal diet supplemented with 0, 0.5, 1, 1.5 and 2% of CLA isomers. Blood samples were collected from fatteners weighing 105 kg. Supplementation of the diet with CLA did not significantly affect lipid parameters in blood plasma. In comparison with gilts, a significantly higher concentration of triglycerides in barrows was found. In CLA-fed pigs, significant changes in the plasma fatty acid profile were noticed. The higher doses of CLA caused a significant increase in CLA and saturated fatty acids (SFA) with a concomitant decrease in monounsaturated (MUFA) and polyunsaturated (PUFA) fatty acids in blood plasma. Moreover, dietary CLA decreased the ∆9 desaturase index in a dose-dependent manner, probably as a result of
Highlights
Conjugated linoleic acid (CLA) comprises an isomeric mixture of linoleic acids [18:2(n-6)] that are polyunsaturated fatty acids differing in the positions and configuration of the conjugated double-bond pairs
The relationships between n-6 and n-3 PUFA are illustrated by their mutual proportions (n-6 PUFA/n-3 PUFA), the decrease of which is inversely proportional to the amount of CLA in the diet
The direct replacement of fatty acids with dietary CLA and its effect on desaturase and lipase activity are probably the main reasons for the changes observed in the fatty acid profile of blood plasma
Summary
Conjugated linoleic acid (CLA) comprises an isomeric mixture of linoleic acids [18:2(n-6)] that are polyunsaturated fatty acids differing in the positions and configuration of the conjugated double-bond pairs. Recent years have seen a growing interest in the effect of CLA on animal metabolism and productivity (Dugan et al, 2004). Interest in these investigations has significantly increased in association with the results of in vivo and in vitro studies showing marked physiological activity of CLA that is of great importance in normal body function and health. CLA has been shown to protect against atherosclerosis and to exert a hypocholesterolaemic effect (Corino et al, 2002). Dietary CLA supplementation has been revealed to increase the activity and function of the immune system (Sugano et al, 1997) and to attenuate the negative effects of inflammatory reactions by inhibiting mRNA expression and production of proinflammatory cytokins by blood cells (Changhua et al, 2004)
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