Hydrogenation of eicosapentaenoic and docosahexaenoic acids and their incorporation into milk fat

In vitro anaerobic incubations were used to assess the extent of hydrogenat ion of eicosapentaenoic acid (C-20:5) and docosahexaenoic acid (C-22:6) n-3 unsaturated fatty acids found in marine oils, Three sources of marine oils - fish oil, squid oil and max-EPA (R)(eicosapentaenoic) were assessed. Abo ut 10-15% of the n-3 fatty acids were hydrogenated when incubated at 38 deg rees C for 24 h anaerobically with sheep rumen fluid at a level exceeding 5 mg/ml (fish oil/rumen fluid). Results from a dose response experiment with fish oil showed a greater capacity of sheep rumen microorganisms to hydrog enate the C-20:5 and C-22:6 when the concentration of fish oil was less tha n 1 mg/ml of rumen fluid. At this level the production of trans C-18:1 fatt y acid war maximum but at higher concentrations of fish oil these isomers d eclined indicating an inhibition of biohydrogenation. Feeding lactating goa ts with either protected or unprotected fish oil increased the proportion o f C-20:5 and C-22:6 n-3 fatty acids in milk. However, further research on t he oil quality, level of supplementation and the degree of ruminal protecti on is required to prevent reduction in feed intake and the resulting suppre ssion in milk fat production. (C) 1999 Elsevier Science B.V. All rights res erved.