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

In vitro anaerobic incubations were used to assess the extent of hydrogenation of eicosapentaenoic acid (C20:5) and docosahexaenoic acid (C22:6) n-3 unsaturated fatty acids found in marine oils. Three sources of marine oils – fish oil, squid oil and max-EPA®(eicosapentaenoic) – were assessed. About 10–15% of the n-3 fatty acids were hydrogenated when incubated at 38°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 hydrogenate the C20:5 and C22:6 when the concentration of fish oil was less than 1 mg/ml of rumen fluid. At this level the production of trans C18:1 fatty acid was maximum but at higher concentrations of fish oil these isomers declined indicating an inhibition of biohydrogenation. Feeding lactating goats with either protected or unprotected fish oil increased the proportion of C20:5 and C22:6 n-3 fatty acids in milk. However, further research on the oil quality, level of supplementation and the degree of ruminal protection is required to prevent reduction in feed intake and the resulting suppression in milk fat production.