Influence of fishmeal, rape-seed, and rape-seed meal in feed on the fatty acid composition and storage stability of porcine body fat

One hundred and ten pigs were fed test diets containing 1·1%, 3·3% or 5·5% fishmeal, 10% rape-seed or 15% rape-seed meal. The control diet contained soya-bean meal. From each carcass M. longissimus dorsi, including subcutaneous fat, was taken and analysed for fatty acid composition and intramuscular fat content. Accelerated oxidation test was carried out on fresh samples. Sensory analyses as well as peroxide and aldehyde analyses were carried out after 0, 4, 6 and 9 months of freezer storage. The sensory properties of fresh meat and fat were not affected by any of the feed components tested. After 6 months of freezer storage slightly increased levels of off-flavours were noted with 3% fishmeal or more in the diet. Also, the peroxide value after storage increased at the same fishmeal level. With rape-seed or rape-seed meal in the diet the scores for off-flavours increased only slightly. A much lower storage stability was noted in fat from pigs fed a combination of rape-seed and fishmeal. Extra vitamin E in diets did not increase the storage stability of pork fat. Special attention was paid to the incorporation of dietary polyunsaturated fatty acids (PUFA), especially marine-PUFA, into body fat. It was found that the incorporation of C22:6 was a very good indicator of the amount of fishmeal in the diet.