Manipulation of the n-3 polyunsaturated fatty acid content of muscle and adipose tissue in lambs1

Abstract

Fifty Suffolk-crossbred wether lambs, with an initial live weight of 29 +/- 2.1 kg, were allocated to one of five concentrate-based diets formulated to have a similar fatty acid content (60 g/kg DM), but containing either linseed oil (high in 18:3n-3); fish oil (high in 20:5n-3 and 22:6n-3); protected linseed and soybean (PLS; high in 18:2n-6 and 18:3n-3); fish oil and marine algae (fish/algae; high in 20:5n-3 and 22:6n-3); or PLS and algae (PLS/algae; high in 18:3n-3 and 22:6n-3). Lambs were slaughtered when they reached 40 kg. Growth performance and intake were similar (P > 0.35) among treatments. By contrast, gain:feed was higher (P < 0.05) in lambs fed the fish oil compared with the linseed oil or PLS/algae diets. Total fatty acid concentration (mg/100 g) in the neutral lipid of the longissimus muscle was not affected by treatment (P > 0.87) but was least (P < 0.05) in the phospholipid fraction in lambs fed the linseed oil diet. Lambs fed either diet containing marine algae contained the highest (P < 0.05) percentage of 22:6n-3 in the phospholipid (mean of 5.2%), 2.8-fold higher than in sheep fed the fish oil diet. In lambs fed the fish/algae diet, the percentage of 20:5n-3 was highest (P < 0.05), contributing some 8.7, 0.8, and 0.5% of the total fatty acids in the muscle phospholipid, neutral lipids, and adipose tissue, respectively. The percentage of 18:3n-3 in the phospholipid fraction of the LM was highest (P < 0.05) in lambs fed the linseed oil diet (6.9%), a value double that of sheep fed the PLS diet. By contrast, lambs fed the PLS diet had twice the percentage of 18:3n-3 in the muscle neutral lipids (3.8%) than those offered the linseed oil diet, and 5.5-fold greater than lambs fed the fish/algae treatment (P < 0.05), an effect that was similar in the adipose tissue. The percentage of 18:2n-6 was highest (P < 0.05) in lambs fed the PLS diet, where it contributed 33.7, 10.1, and 11.2% in the muscle phospholipid, neutral lipids, and adipose tissue, respectively. The highest (P < 0.05) muscle PUFA-to-saturated fatty acid (P:S) ratio was obtained in lambs fed the PLS diet (0.57), followed by the PLS/algae diet (0.46), and those fed the fish oil or linseed oil diets had the lowest ratios (0.19 and 0.26, respectively). The favorable P:S ratio of lambs fed the PLS/algae diet, in conjunction with the increased levels of 20:5n-3 and 22:6n-3, enhanced the nutritional qualities of lamb to more closely resemble what is recommended for the human diet.

Effects of supplementation with fish oil and barium selenate on performance, carcass characteristics and muscle fatty acid composition of late season lamb finished on grass-based or concentrate-based diets

“…Despite the low inclusion level and extensive bio-hydrogenation of long-chain PUFA in sheep (.0.87; Sinclair et al, 2005), including fish oil in the diets of housed lambs led to a 3.2-fold increase in docosapentaenoic acid content and a 15.6-fold increase in DHA content of lamb meat. However, because of the low prevalence of these fatty acids in the lamb meat, fish oil had no significant effects on total n-3 content, PUFA : SFA ratio or the n-6 : n-3 ratio of the meat, which contrasts with earlier reports by Wachira et al (2002) and Cooper et al (2004). Intake of fish oil by GF lambs was proportionately 0.32 of the level for HF lambs because of restricted feeding of concentrates.…”

“…As a result of using early-maturing hill breed types in this study, fat content of the L. dorsi (range 42 to 65 mg/g tissue) was higher than levels previously reported in lambs (Wachira et al, 2002;Cooper et al, 2004). Significant breed effects on the fatty acid composition of lamb meat have also been reported (Fisher et al, 2000;Demirel et al, 2004) and could explain the lower PUFA : SFA ratios (0.06 to 0.13) and higher n-6 : n-3 ratios (2.58 to 4.44) observed here.…”

Effect of grazing pastures with different botanical composition by lambs on rumen fatty acid metabolism and fatty acid pattern of longissimus muscle and subcutaneous fat

“…Animals presented a low total amount of FA in the subcutaneous fat, compared with results of Enser et al (1996), Wachira et al (2002) and Cooper et al (2004). This is most probably related to contamination of the subcutaneous fat by connective tissue.…”

Centesimal composition and fatty acids of meat from lambs fed diets containing soybean hulls

“…In lambs fed concentrate or forage, polyunsaturated fatty acids in the diet are biohydrogenated in the rumen, resulting in the predominant absorption of saturated fatty acids by the intestine. This is one of the reasons why lamb meat is characterized by high concentrations of saturated fatty acids and low ratio of PUFA:SFA (Cooper et al, 2004).…”