2005). The effects of sh oil supplementation on rumen metabolism and the biohydrogenation of unsaturated fatty acids in beef steers given diets containing sunower oil. AbstractDuodenally and ruminally fi stulated steers were offered grass silage and one of three concentrates at a ratio of 60 : 40 (forage : concentrate on a dry-matter basis) : F0, F1 or F4 at 14 g/kg live weight. The concentrates were designed to be iso-lipid and to provide the same amount of sunfl ower oil but increasing amounts of fi sh oil : 0, 1 and 4 g per 100 g, respectively. Ruminal characteristics were measured along with fatty acid intakes and duodenal fl ows to determine the effect of fi sh oil on : ruminal pH, ammonia-N concentration, volatile fatty acid ( VFA) concentration and polyunsaturated fatty acid ( PUFA) metabolism. Fish oil had no signifi cant effect on ruminal pH, ammonia-N concentration or the molar proportions of the major VFA, although total VFA concentration was signifi cantly reduced at the highest level of fi sh oil inclusion. Fish oil signifi cantly increased the fl ow of long chain PUFA, total conjugated linoleic acid and vaccenic acid to the duodenum and decreased the fl ow of stearic acid. Biohydrogenation, as determined by the net loss of fatty acid between the mouth and duodenum, of oleic and linolenic acid was not affected by fi sh oil inclusion and averaged 0·64 and 0·92, respectively. There was a small increase in the biohydrogenation of linoleic acid with increasing fi sh oil from 0·89 to 0·92 ( P<0·01) on F0 and F4, respectively. Biohydrogenation of the long chain PUFA C20 : 5(n-3) and C22 : 6(n-3) increased from 0·49 and 0·74 to 0·79 and 0·86 ( P increased from 0·49 and 0·74 to 0·79 and 0·86 ( P increased from 0·49 and 0·74 to 0·79 and 0·86 ( <0·01), respectively when fi sh oil in the concentrate increased from 1 to 4 g per 100 g. The net effect of fi sh oil on lipid metabolism appears to inhibit the transition of vaccenic acid to stearic acid in the rumen resulting in a build up of this intermediate in the biohydrogenation pathway of C18 PUFA.

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The objective of this study was to evaluate the impact of diets enriched with plant oils or seeds, high in polyunsaturated fatty acids (PUFA), on the fatty acid profile of sheep intramuscular and subcutaneous adipose tissue (SAT). Sixty-six lambs were blocked according to initial body weight and randomly assigned to six concentrate-based rations containing 60 g fat/kg dry matter from different sources: (1) Megalac (MG; ruminally protected saturated fat), (2) camelina oil (CO), (3) linseed oil (LO), (4) NaOH-treated camelina seed (CS), (5) NaOH-treated linseed (LS) or (6) CO protected from ruminal saturation by reaction with ethanolamine; camelina oil amides (CA). The animals were offered the experimental diets for 100 days, after which samples of m. longissimus dorsi and SAT were collected and the fatty acid profile determined by GLC. The data were analyzed using ANOVA with 'a priori' contrasts including camelina v. linseed, oil v. NaOH-treated seeds and CS v. CA. Average daily gain and total fatty acids in intramuscular adipose tissue were similar across treatments. The NaOH-treatment of seeds was more effective in enhancing cis-9, trans-11 conjugated linoleic acid (CLA) incorporation than the corresponding oil, but the latter resulted in a higher content of trans-11 18:1 in both muscle neutral and polar lipids ( P , 0.01, P , 0.001, respectively). Inclusion of LS resulted in the highest PUFA : saturated fatty acid (SFA) ratio in total intramuscular fat (0.22). The NaOH-treatment of seeds resulted in a higher PUFA/SFA ratio (0.21 v. 0.18, P , 0.001) than oils and on average, linseed resulted in a higher PUFA/SFA ratio than camelina ( P , 0.01). Lambs offered LS had the highest concentration of n-3 PUFA in the muscle, while those offered MG had the lowest ( P , 0.001). This was reflected in the lowest ( P , 0.001) n-6: n-3 PUFA ratio for LS-fed lambs (1.15) than any other treatment, which ranged from 2.14 to 1.72, and the control (5.28). The trends found in intramuscular fat were confirmed by the data for SAT. This study demonstrated the potential advantage from a human nutrition perspective of feeding NaOH-treated seeds rich in PUFA when compared to the corresponding oil. The use of camelina amides achieved a greater degree of protection of dietary PUFA, but decreased the incorporation of biohydrogenation intermediates such as cis-9, trans-11 CLA and trans-11 18:1 compared to NaOH-treated seeds.

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