Ruminal biohydrogenation of unsaturated fatty acids in vitro as affected by chitosan

Abstract

Because of the health-promoting effects of conjugated linoleic acid (CLA) isomers in humans, there is growing interest in increasing the content of C18:1 t11 in the rumen in order to enhance the final CLA level in ruminant milk and meat products. Modifying ruminal microflora populations has been viewed as a means to increase their C18:1 t11 content. Therefore, the objective of this experiment was to identify whether chitosan, a natural antimicrobial agent, could be used to modify the biohydrogenation intermediates of two fat sources. The study used a Rusitec unit consisting of eight vessels, and the diets were grass hay and a concentrate mixture (10:90) formulated using either sunflower or rapeseed meal as a fatty acid (FA) source. The incubation experiment consisted of a 6-day adaptation followed by a 5-day chitosan dosing period (750 mg/d), sampling for FA profile and pH determination on the last 3 days. Chitosan interfered in FA biohydrogenation, decreasing total C18:0 (48.7 g/100 g FA versus 23.2 g/100 g FA; P < 0.01) and increasing total C18:1 (5.4 g/100 g FA versus 25.8 g/100 g FA; P < 0.05), C18:1 t11 (4.5 g/100 g FA versus 19.6 g/100 g FA; P < 0.05), total CLA (0.17 g/100 g FA versus 0.37 g/100 g FA; P < 0.05), t9t11 CLA (0.10 g/100 g FA versus 0.21 g/100 g FA; P < 0.05), and the C18:1 t11/C18:0 ratio (0.09 g/100 g FA versus 0.89 g/100 g FA; P < 0.05). Compared to sunflower meal, when rapeseed meal was incubated as the fat source in the concentrate mixture, only total C16:0 was decreased (22.9 g/100 g FA versus 20.6 g/100 g FA; P < 0.05). Chitosan supplementation increased proportions of C18:1 c9, C18:1 c11, and t10c12 CLA only when rapeseed meal was used as the fat source in the concentrate mixture. Chitosan was very effective at inhibiting biohydrogenation in vitro by increasing C18:1 t11 and total CLA proportions and lowering the proportion of saturated FA, regardless of the FA source. However, chitosan increased other biohydrogenation intermediates to a greater extent with rapeseed meal as the dietary fat source.