| Five in vitro trials were carried out to investigate effects of free unsaturated fatty acid mixture (FFAM) and vegetable oils on ruminal fermentation, biohydrogenation of C18UFA and accumulation of Precursors (cis-9, trans-UCLA and TC18:1) of conjugated linoleic acid (CLA) of bovine milk by ruminal microbial mixture. Incubating condition was set as liquid media, little dose of inoculum (5%) , 39℃ and 0.5g cellulose powder. Volume of culture per bottle was 100ml and Amount of oil or FFAM addition was based on this volume in every trial.Control, 20mg FFAM-A and FFAM-B treatments were arranged in trial one to investigate fermentation properties of ruminal microbial mixture in vitro during 0-90h of incubating period. Varying trends of pH and TVFA concentration with incubation proceeding indicated that the ideal period to investigate fermentation of ruminal microbes is from Oh to 60h and 20mg FFAM inhibited fermentation severely.Trial two was designed to study effects of FFAM (A and B) adding levels (5-20mg) on fermentation of ruminal microbes and biohydrogenation of C18UFA at 60h. Trial three was designed to study evolution of C18UFA biohydrogenation as well as accumulation of intermediate products during the period of 0-60h when 5mg FFAM-A or FFAM-B was added. Differences of effects of 5mg vegetable oils and FFAM on ruminal fermentation and C18UFA biohydrogenation at 60h were investigated in trial 4. Trial five were arranged to research effects of kinds (soybean oil, cottonseed oil, canola oil and linseed oil) and adding levels (Omg, 5mg, lOmg, 15mg, 20mg, 25mg) of vegetable oils on ruminal fermentation, biohydrogenation of CigUFA and accumulation of intermediate products at 60h. Results were as follows:1) Disappearances of cellulose powder at 24h were only 20%-25% of those at 60h, which indicated degradation of cellulose occurred mainly during 24-3 6h. Compared with control, 5mg FFAM-A and FFAM-B had disappearance of cellulose powder descended 27.3% and 35.3%, individually and the degree of inhibition to cellulose disappearance reached 90% when adding level of FFAM-A went up to 15mg or that of FFAM-B rose to 10mg. Accordingly, there existed no difference (P>0.05) of TVFA concentration between Control and two 5mg FFAM treatments at 24h while TVFA concentrations of 5mg FFAM were lower (P<0.05) than that of control at 60h.2) Compared with control, 5mg vegetable oils had pH, TVFA concentration and disappearance of cellulose changed little (P>0.05). Linseed oil, soybean oil, cottonseed oil and canola oil inhibited cellulose degradation significantly when adding level reached 10mg, 15mg, 20mg and 25mg, individually. The competence of FFAM-A inhibiting cellulose degradation is 9.3 times of that of soybean oil.3) In FFAM as well as vegetable oil treatments, disappearances of C18:3n-3 were higher than those of C18:2n-6 (P<0.01) as well as disappearances of C18:2n-6 wereinhigher than those of C18:l (P<0.01). disappearance of C18:2n-6 in FFAM-B was lower than that in FFAM-A (p<0.01) and disappearance of C18:2n-6 in linseed oil was lower than that in soybean oil and canola oil (p<0.01).4) With adding level increasing, conversion rates of all the reaction steps related to biohydrogenation of C18UFA descended and those of C18:3n-3 to C18:2n-3, C18:2n-6 to CLA and CLA to TC18:1 lowered with small extent while those of C18:2n-3 to TC18:1 and TC18:1 to C 18:0 descended more quickly. CLA proportion in total fatty acids (TFA) reached peak at 6h in two FFAM treatments. TC18:1 proportion in TFA reached peak in 24h and then descended slowly in 5mgFFAM-A. C18:2n-3 proportion in TFA reached peak at 12h and TC18:1 ratio increased significantly till 36h in 5mg FFAM-B.5) At 5mg level, hydrogenating completeness of linseed oil, soybean oil, cottonseed oil and canola oil were 90.02%, 93.00%, 93.70% and 94.36%, individually while completeness of FFAM-A and FFAM-B were only 37.36% and 23.62% individually. With adding level increasing, completeness of biohydrogenation of all kinds of vegetable oils decreased...
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