Animal Science Abstract
Effect of breed on the deposition in beef muscle and adipose tissue of dietary n-3 polyunsaturated fatty acids
N. J. Choi1,2, M. Enser2, J. D. Wood2 and N. D. Scollan1
1Institute of Grassland and Environmental Research, Plas Gogerddan, Aberystwyth SY23 3EB, UK2Division of Food Animal Science, School of Veterinary Science, University of Bristol, Langford, Bristol BS40 5DU, UK
Abstract
This study investigated the effects of dietary n-3 polyunsaturated fatty acids (PUFA) on muscle fatty acid composition and content in two cattle breeds; the Holstein-Friesian, a dairy breed, and the Welsh Black, a traditional beef breed. Animals were kept on ad libitum grass silage and one of three concentrates varying in the source of fat; Megalac (high in C16 : 0), formaldehyde treated whole linseed (high in C18 : 3 n-3) and a combination of formaldehyde treated whole linseed and fish oil (high in C20 : 5 n-3 and C22 : 6 n-3). The concentrates were offered at approximately 0·4 of total dry matter intake. Samples of m. longissimus thoracis from Holstein-Friesians contained higher total amounts of fatty acids (P < 0·05) than that of Welsh Blacks in neutral lipid, but the phospholipid fatty acid content was similar between the breeds. Over all treatments, the proportion of C18 : 3 n-3 was higher (P < 0·001) in muscle neutral lipid of Welsh Blacks and the proportions of C18 : 3 n-3 and C18 : 1 trans were higher (P < 0·05 and P < 0·001, respectively) in their subcutaneous adipose tissue. Feeding linseed increased the amounts of C18 : 3 n-3 and also C20 : 5 n-3 in muscle phospholipids suggesting chain elongation and desaturation of C18 : 3 n-3 had occurred. The concentration of C20 : 5 n-3 was significantly higher (P < 0·05) in muscle phospholipids of Welsh Blacks while no differences were found for C18 : 3 n-3 and C22 : 6 n?3. However, when expressed as a proportion of total fatty acids, both C20 : 5 n-3 and C18 : 3 n-3 were significantly higher (P < 0·001) in the Welsh Black phospholipids. These differences resulted in a significantly higher P : S ratio of the muscle total fat (P < 0·05) in the Welsh Black than in the Holstein-Friesian but P : S was not affected by diet. On the other hand, the n-6 : n-3 PUFA ratio was significantly lower in the Welsh Black, reflecting the higher n-3 PUFA content. This ratio was lower in the linseed and the mixed treatments for both breeds, reflecting higher delivery of n-3 PUFA from these diets. Fortification of the diet with sources of PUFA and exploiting breed differences offer the potential to develop systems to increase human intakes of n-3 PUFA in line with current nutritional recommendations.
Keywords: beef, breeds, lipids, polyenoic fatty acids
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