Effect of breed on the deposition in beef muscle and adipose tissue of dietary n-3 polyunsaturated fatty acids

This study investigated the effects of dietary n-3 polyunsaturated fatty ac ids (PUFA) on muscle fatty acid composition and content in two cattle breed s; 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),formald ehyde treated whole linseed (high in C18: 3 n-3) and a combination of forma ldehyde 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 matt er intake. Samples of m. longissimus thoracis from Holstein-Friesians conta ined higher fetal amounts of fatty acids (P < 0.05) than that of Welsh Blac ks in neutral lipid, hut the phospholipid fatty acid content was similar be tween the breeds. Over all treatments, the proportion of C18 : 3 n-3 was hi gher (P < 0.001) in muscle neutral lipid of Welsh Blacks and the proportion s of C18 : 3 n-3 and C18 : 1 trans were higher (P < 0.05 and P < 0.001, res pectively) in their subcutaneous adipose tissue. Feeding linseed increased the amounts of C18 : 3 n-3 and also C20 : 5 n-3 in muscle phospholipids sug gesting 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 wen found for C18 : 3 n- 3 and C22 : 6 n-3. However, when expressed as a proportion of total fatty a cids, 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 signifi cantly higher P : S ratio of the muscle total fat (P < 0.05) in the Welsh B lack than in the Holstein-Friesian but P : S was not affected by diet. On t he other hand, the n-6 : n-3 PUFA ratio was significantly lower in the Wels h Black, reflecting the higher n-3 PUFA content. This ratio was lower in th e linseed and the mixed treatments for both breeds, reflecting higher deliv ery of n-3 PUFA from these diets. Fortification of the diet with sources of PUFA and exploiting breed differences offer the potential to develop syste ms to increase human intakes of n-3 PUFA in line with current nutritional r ecommendations.