In France, AFSSA guidelines based on Recommended Nutritional Intakes (RNI, 2001) are tending towards increasing the consumption of omega 3 fatty acids and reducing the intake of omega 6 fatty acids, so as to achieve an omega-6/omega-3 ratio close to 5. At present, the consumption of omega 3 is estimated at 800/900 mg a day, while the recommended quantity is 2 g/day. There is thus a role to play for dietary vectors that provide omega 3 fatty acids.
In the case of pork, different husbandry factors will strongly influence the lipid component in meat, both in terms of the quantity of lipids deposed and the fatty acid composition. Researchers in the Joint Research Unit for Livestock Production Systems, Animal and Human Nutrition (SENAH) at INRA in Rennes have considered this feature in terms of improving meat quality by introducing fatty acids deemed beneficial to human health into the feed of animals. They initiated a study to measure the effect on meat quality of incorporating extruded linseed, a source of omega 3 fatty acids, with particular focus on the deposition of alpha-linolenic acid and its derivatives, such as EPA and DHA.
Alpha-linolenic acid is the precursor of fatty acids that play a particularly important biological role in the body, such as eicosapentaenoic acid (EPA and docosahexaenoic acid (DHA). These fatty acids are not found in products of animal origin. Thus the simple addition of alpha-linolenic acid to the human diet (for example, by using plant oils containing high levels of this fatty acid) is not sufficient to protect the cardiovascular system, because the body also needs the EPA and DHA that are provided through the ingestion of animal products as it cannot synthesise them from alpha-linolenic acid.
For the purposes of the study, the INRA scientists constituted two groups of 40 pigs which received isolipidic and isoenergetic diets containing different sources of lipids and differing levels of fatty acids: one feed based on 2.5% sunflower oil and a linseed feed containing 5% extruded linseed. These fats are characterised by their different polyunsaturated fatty acid contents. The alpha-linolenic acid content was 3.6% with sunflower oil and 19.9% with extruded linseed.
The results showed that pigs that had received extruded linseed presented with more omega 3 fatty acids and higher levels of EPA and DHA in their tissues. The incorporation of linseed in the ration increased omega 3 levels in both the adipose tissue of the back and the Longissimus dorsi muscle (the principal meat used for pork roasts). The omega-6/omega-3 ratio was lower in pigs receiving extruded linseed; it was reduced from 12 to 4.5 in the Longissimus dorsi and from 11 to 3 in adipose back tissues. In the Longissimus dorsi muscle, the percentage of ALA was multiplied threefold, that of EPA fourfold and that of DHA twofold, when compared with pigs receiving the sunflower oil diet.
The sunflower oil diet was characterised by high levels of oleic and linoleic acids, and more generally by higher levels of monounsaturated fatty acids, with an omega-6/omega-3 ratio close to 15. This could be explained by the very high levels of omega 6 contained in sunflower oil.
Establishing the relationship between lipids ingested by animals and those deposited in tissues thus showed that it is possible to improve pork meat quality, and particularly its omega 3 fatty acid content, by including extruded linseed in animal feed. The researchers are also studying the fate of these fatty acids during product processing, and consumer perceptions regarding these products, in order to verify whether the high levels of omega 3 in these meats are sustained after processing into charcuterie products and do not alter their sensory qualities.
References :
C. Corino, M. Musella, J. Mourot : "Influence of extruded linseed on growth, carcass composition, and meat quality on slaughetered pigs at one hundred ten and one hundred sixty kilograms of liveweight."
Journal of Animal Science, 2008.86:1-11
doi:10.2527/jas.2007-0155
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