Effects of two supplementation levels of linseed combined with CLA or tallow on meat quality traits and fatty acid profile of adipose and different muscle tissues in slaughter pigs.

Dietary linseed supply efficiently elevates the linolenic acid concentration of pork. The main problem of increasing the n-3 fatty acid tissue levels arises from a higher susceptibility to lipid oxidation. Increasing the saturation level of tissue lipids by the dietary inclusion of conjugated linoleic acids (CLA) or tallow might prevent oxidation. Thus, the aim of the study was to evaluate the impact of dietary CLA or tallow supplementation combined with extruded linseed on the growth performance, carcass characteristics and fatty acid profile of muscles (longissimus, semimembranosus, biceps femoris) and subcutaneous fat (SF). The enzyme activity of the de novo lipogenesis and stearoyl-CoA desaturase in the SF was also assessed. From 18 to 104 kg BW, 32 Swiss Large White barrows were fed a diet supplemented with either: (1) 2% linseed (L2); (2) 3% linseed (L3); (3) 2% linseed + 1% CLA (L2-C) or (4) 2% linseed + 1% tallow (L2-T). The linolenic and eicosatrienoic acid concentrations were higher (P < 0.01) and the ∑n-6/∑n-3 ratio was lower (P < 0.01) in all tissues of L3 than L2 and L2-T barrows. Only in the SF the docosapentaenoic acid concentration was increased (P < 0.01) in L3 barrows. Compared with the other three diets, feeding the L2-C diets increased (P < 0.01) the amount of myristic, palmitic, stearic and palmitoleic acid at the expense of the oleic and eicosenoic acid content in the intramuscular and SF lipids. Except for the lower (P < 0.05) eicosadienoic acid concentration in the muscles, feeding the L2-C treatment resulted in similar polyunsaturated fatty acid concentrations and ∑n-6/∑n-3 ratio than feeding L2 or L2-T diets. Both the c9,t11- and t10,c12-CLA isomers found in the CLA-supplemented diet were also detected in the tissues, but the c9,t11-isomer was more abundant than the t10,c12-isomer. De novo lipogenesis was not (P > 0.05) affected by the dietary fats, whereas Δ9-desaturase activity was depressed (P < 0.05) by CLA inclusion (L2-C). Only when oxidation was challenged by cooking and subsequent storage for 4 days at 4°C values of thiobarbituric acid-reactive substances were lower (P < 0.05) in longissimus muscle chops of L2-C compared with L2, L3 and L2-T barrows. The present findings revealed that CLA, but not tallow, combined with extruded linseed enhanced the oxidative stability of pork probably by lowering the degree of unsaturation of the lipids without affecting the improved ∑n-6/∑n-3 ratio.