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The effects of the type of grass silage and dietary inclusion of fish oil (FO) on the fatty acid profile of bovine intramuscular and subcutaneous adipose tissue were investigated. Eighty Friesian steers were assigned (n 10) to unwilted or wilted silage, and to one of four rations which contained, per kg, 80??g of sunflower oil and either 0, 10, 20 or 40??g of FO replacing lard. Animals were slaughtered after 108??d and the fatty acid profile of the neutral, polar and total lipid fractions of the M. longissimus dorsi, and the total lipid fraction of the subcutaneous adipose tissue were determined. Wilting of grass prior to ensiling increased the concentration of conjugated linoleic acid (CLA) in intramuscular total lipid (P??

Enhancing the polyunsaturated fatty acid (PUFA) and decreasing the saturated fatty acid content of beef is an important target in terms of improving the nutritional value of this food for the consumer. The present study examined the effects of feeding a ruminally protected lipid supplement (PLS) rich in PUFA on the fatty acid composition of longissimus thoracis muscle and associated subcutaneous adipose tissue. Animals were fed ad libitum on grass silage plus one of three concentrate treatments in which the lipid source was either Megalac (rich in palmitic acid; 16:0) or PLS (soyabean, linseed and sunflower-seed oils resulting in an 18:2n???6:18:3n???3 value of 2??4:1). Treatment 1 contained 100g Megalac/kg (Mega, control); treatment 2 (PLS1) contained 54g Megalac/kg with 500g PLS/d fed separately; treatment 3 (PLS2) contained no Megalac and 1000g PLS/d fed separately. The PLS was considered as part of the overall concentrate allocation per d in maintaining an overall forage:concentrate value of 60:40 on a DM basis. Total dietary fat was formulated to be 0??07 of DM of which 0??04 was the test oil. Total intramuscular fatty acids (mg/100g muscle) were decreased by 0??31 when feeding PLS2 compared with Mega (P<0??05). In neutral lipid, the PLS increased the proportion of 18:2n???6 and 18:3n???3 by 2??7 and 4??1 on diets PLS1 and PLS2 v. Mega, respectively. Similar responses were noted for these fatty acids in phospholipid. The amounts or proportions of 20:4n???6, 20:5n???3 or 22:6n???3 were not influenced by diet whereas the amounts and proportions of 22:4n???6 and 22:5n???3 in phospholipid were decreased with inclusion of the PLS. The amounts of the saturated fatty acids, 14:0, 16:0 and 18:0, in neutral lipid were on average 0??37 lower on treatment PLS2 compared with Mega. Feeding the PLS also decreased the proportion of 16:0 in neutral lipid. The amount of 18:1n-9 (P=0??1) and the amount and proportion of 18:1 trans (P<0??01) were lower on treatments PLS1 and PLS2 in neutral lipid and phospholipid. Conjugated linoleic acid (cis-9, trans-11) was not influenced by diet in the major storage fraction for this fatty acid, neutral lipid. The PUFA:saturated fatty acids value was increased markedly (??2??5) with inclusion of the PLS (P<0??001) while the ??n???6:n???3 value increased slightly (??1??2; P=0??015). The results suggest that the protected lipid used, which was rich in PUFA, had a high degree of protection from the hydrogenating action of rumen micro-organisms. The PLS resulted in meat with a lower content of total fat, decreased saturated fatty acids and much higher 18:2n???6 and 18:3n???3. The net result was a large shift in polyunsaturated: saturated fatty acids, 0??28 v. 0??08, on feeding PLS2 compared with Mega, respectively. [ABSTRACT FROM PUBLISHER]

Seventy-two 8-week-old ram lambs from three breeds, Suffolk, Soay and Friesland, were offered one of four diets based on dried grass and formulated to have a similar fatty acid content (60 g/kg DM) and containing: Megalac (high in 16 : 0, control; Volac Ltd, Royston, Herts., UK), whole linseed (18 : 3n-3), fish oil (20 : 5n-3 and 22 : 6n-3) or whole linseed plus fish oil. The lambs were slaughtered at approximately half of their mature live weight (43, 21 and 43 kg for Suffolk, Soay and Friesland lambs, respectively). Fish oil reduced DM intake and lamb live-weight gain (P<0??001), while DM intake, live-weight gain and subcutaneous fat content were highest in Suffolk and lowest in Soay lambs. Linseed feeding doubled the proportion (??100) of 18 : 3n-3 in the longissimus dorsi from 1??4 to 3??1 and in the subcutaneous adipose tissue from 1??2 to 2??6 (P<0??001). Suffolk and particularly Soay lambs contained higher proportions of 18 : 3n-3 than Friesland lambs in the longissimus dorsi, while in the adipose tissue, Suffolk lambs had the highest level. Feeding fish oil increased the muscle proportion (??100) of 20 : 5n-3 from 0??7 to 2??3 and 22 : 6n-3 from 0??3 to 0??8 (P<0??001). By contrast, the proportions of the longer-chain n-3 polyunsaturated fatty acids were similar across all three breeds. All three lipid supplements containing n-3 polyunsaturated fatty acids increased the content of muscle trans-18 : 1 relative to the control values, but conjugated linoleic acid (cis-9,trans-11???18 : 2) only increased in the muscle of lambs fed linseed. Feeding linseed or fish oil lowered the n-6 : n-3 ratio in sheep meat, but neither diet nor breed had much effect on the polyunsaturated fatty acid: saturated fatty acid ratio. [ABSTRACT FROM PUBLISHER]

Enhancing the n-3 polyunsaturated fatty acid (PUFA) content of beef is important in view of the generally saturated nature of fatty acids in ruminant meats and the negative effect this can have on human health. This study examined the effects of different sources of dietary n-3 PUFA on the performance of steers and the fatty acid composition of m. longissimus thoracis muscle and associated subcutaneous adipose tissue. Animals were fed ad libitum on grass silage plus one of four concentrates (60:40 forage:concentrate on a DM basis) containing differing sources of lipid: Megalac (16:0), lightly bruised whole linseed (18:3n-3), fish oil (20:5n-3 and 22:6n-3) and a mixture of linseed and fish oil (1:1, on an oil basis). Diets were formulated so that total dietary oil intake was 6 %, approximately half of which was from the experimental test oil. Linseed feeding not only increased the levels of 18:3n-3 in muscle phospholipid from 9·5 to 19 mg/100 g muscle but also enhanced the synthesis of 20:5n-3, the level of which increased from 10 to 15 mg/100 g muscle. Linseed also increased the proportion of 18:3n-3 in muscle neutral lipid and in adipose tissue lipids by a factor of 1·64 and 1·75 respectively. Fish oil feeding doubled the proportion of 20:5n-3 and 22:6n-3 in muscle phospholipids. The proportion of 18:1 trans in muscle neutral lipid was higher on the n-3 PUFA diets than the control diet, 0·04 and 0·02 respectively. Despite the implied modification to rumen metabolism, lipid source did not affect feed intake, growth rate, cold carcass weight or carcass fatness, but carcass conformation score was higher on fish oil treatments (P<0·05). However, total muscle fatty acid content was not different between treatments and ranged from 3·5–4·3 % of tissue weight. The increase in n-3 PUFA in the meat produced by feeding linseed or fish oil lowered the n-6:n-3 ratio but had little effect on the P:S ratio. [ABSTRACT FROM PUBLISHER]