Effect of conjugated linoleic acid on energy metabolism in growing‐finishing pigs

Abstract

SummaryThe effect of conjugated linoleic acid (CLA) on energy metabolism was studied in a respiration experiment with 20 growing pigs. From 70 kg liveweight onwards the animals received isoenergetic rations containing 0 or 3% CLA on the basis of metabolic bodyweight. Between 95 and 100 kg liveweight the gas exchange of each animal was measured over 48 h in a respiration chamber. This was preceded by a 5‐day quantitative determination of faeces and urine. The heat production and energy retention of the animals were determined by the carbon–nitrogen balance technique and the RQ method. Additionally several parameters of blood serum were determined. CLA had no effect on digestibility and metabolizability of energy, nor were gas exchange and heat production (HP) of the animals affected by the treatment. Average heat production across all measurements was 628 kJ/kg W0.75 in the control group and 636 kJ/kg W0.75 in the CLA group. No difference in fat deposition was observed (control 386, CLA group 379 kJ/kgW0.75). The N balance on the other hand was 2.2 g/day higher in the CLA‐supplemented animals. This caused retained protein energy, as a proportion of total energy retention, to increase from 24.2 to 25.8%. The ratio of retained protein energy to fat energy was 10% higher in the CLA‐treated animals than in the controls. Body mass increase over the trial as a whole was unaffected (control 27.6, CLA group 28.1 kg, equivalent to daily gains of 931 and 946 g, respectively). Blood serum lipoproteins exhibited few CLA‐induced changes. The greatest effects were observed in triacylglycerols, which were raised in the CLA animals compared with the controls. The ratio of cholesterol‐low‐density lipoprotein to cholesterol‐high‐density lipoprotein rose by 17% as a result of CLA treatment. Serum concentrations of albumin, creatinine, urea and glucose were unchanged. In conclusion, the study showed that supplementation with CLA under isoenergetic feeding conditions with a strongly positive energy balance has no marked effect on total metabolism, although a slightly enhanced deposition of protein was evident.