0
One hundred and fifty four crossbred pigs with an initial average BW of 36.4 kg were randomly allotted to 7 feeding groups. Each group was housed in 2 pens of 11 animals of mixed sexes. The experimental trial was divided in two different phases during the growing-fattening period: Phase 1 (8 weeks; until approximately 70 kg) and Phase 2 (variable duration: 6 or 8 weeks; until an approximate slaughter weight of 100 kg), therefore according two the different duration of phase 2 the entire experiment lasted 14 or 17 weeks. All diets were based on barley, wheat, and soybean meal. In the basal diet (B), only animal fat was used as fat source. In diets containing linseed oil (L; α-LNA supply) and fish oil (F; EPA and DHA supply), linseed or fish oil was added, to provide 1.2% oil (as fed) at the expense of animal fat. Three dietary groups were supplied the same fatty acid source during both fattening phases (groups BB, LL, and FF). For the other 4 dietary groups, the fatty acid source was switched after the first phase (groups BL, BF, LF, and FL; the first and second letter indicating the diet in P1 and P2, respectively). The longissimus thoracis muscle (LT) was analyzed for fatty acid composition; lipid stability (thiobarbituric acid-reactive substances) and colour stability (a* value, % of myoglobin pigments) were determined on the LT after illuminated chill storage for up to 8 d.
The α-linolenic acid, EPA, and DHA incorporation was independent of the duration of linseed feeding (1.24, 0.54, and 0.75% of total fatty acids, respectively, for group LL). Supplying fish oil during both phases resulted in the greatest EPA and DHA proportions (1.37 and 1.02% of total fatty acids; P < 0.05), but the content of DHA was not affected. The proportion of DHA was greater when fish oil was administered during P2 compared with P1 (P < 0.05). There was no effect of diet on meat ultimate pH and drip loss or on colour or lipid oxidation.
It is concluded that meat and lipid quality it is not affected by the inclusion of linseed or fish oil in the diet, however the effects of duration and time of feeding of an specific fat source on the muscle fatty acid composition is dependent on the fatty acids considered.
L Haak, S De Smet, D Fremaut, K Van Walleghem and K Raes. 2008. Journal of Animal Science. 86:1418-1425.
