Whole-body retention of α-linolenic acid and its apparent conversion to other n-3 PUFA in growing pigs are reduced with the duration of feeding α-linolenic acid.

ABSTRACT

In the present study, fifteen growing pigs were used to determine the whole-body oxidation, retention efficiency (RE) and apparent conversion (AC) of α-linolenic acid (18 3n-3) to n-3 highly unsaturated fatty acids (HUFA), including EPA (20 5n-3) and DHA (22 6n-3). The pigs were fed a diet containing 10% flaxseed for 30 d. Whole-body fatty acid composition was determined at initial (27.7 (SE 1.9) kg), intermediate (day 15; 39.2 (SE 1.4) kg) and final (45.7 (SE 2.2) kg) body weight. On day 12, four pigs were fed 10 mg/kg of uniformly labelled (13)C-18 3n-3 (single-bolus dose) to determine the oxidation of 18 3n-3. Expired CO2 samples were collected for 24 h thereafter. The whole-body content of n-3 PUFA increased linearly (P< 0.0001) with time; however, the content of 22 6n-3 exhibited a quadratic response (P< 0.01) with a peak occurring at 15 h. As a proportion of intake, the RE of 18 3n-3 tended to reduce with time (P = 0.098). The AC of ingested 18 3n-3 to the sum of n-3 HUFA was reduced with time (P< 0.05; 12.2 v. 7.53 % for days 0-15 and days 15-30, respectively). The AC of 18 3n-3 to 20 5n-3 or 22 6n-3 was lower than that to 20 3n-3, both for days 0-15 (P < 0.05; 1.14 or 1.07 v. 7.06 %) and for days 15-30 (P< 0.05; 1.51 or 0.33 v. 4.29 %). The direct oxidation of 18 3n-3 was 7.91 (SE 0.98) % and was similar to the calculated disappearance of 18 3n-3 between days 0 and 30 (8.81 (SE 5.24) %). The oxidation of 18 3n-3 was much lower than that reported in other species. The AC of 18 3n-3 to n-3 HUFA was reduced over time and that to 20 3n-3 in the present study was much higher than that reported in other species and should be explored further.