Effects Of Soybean Oil And Linseed Oil Supplementation On Population Of Ruminal Bacteria And Fermentation Parameters In Dairy Cows

Basis on nutrition and fatty acid profiles of 20 concentrate and forage feed for dairy cow tested by chemical analytical method and gas chromatography, the objective of this study was to evaluate changes of ruminal fermentation parameters, the activities of filter paper and lipases, and rumen bacteria population colony counts by hungate roll tube technique and quantification of bacteria DNA by real time PCR approach during supplementation of soybean oil and linseed oil. Four primiparous Holstein cows (BW = 521±38kg, DIM averaged 45±10d) fitted with permanent ruminal and duodenal T-type cannulas were randomly assigned to 4 treatments in a 4×4 Latin square design with 12-wk. Cows in four treatments were fed a basal diet containing 60% forage and 40% concentrate either without oil supplement (CK), 4% soybean oil (LOC1), 4% linseed oil (LOC2) or 2% soybean oil plus 2% linseed oil (LOC3) of dry matter basis.In experiment 1, fatty acid profiles of concentrate and forage contained saturated fatty acid and unsaturated fatty acid, while C16 and C18 fatty acid were main. Fatty acid trait in different source of feed showed difference, C18:0 contents in feed were mostly under 10%, energy and protein feed riched in C18: land C18:2, while C18:3 contents were higher than those of other fatty acids in forage.In experiment 2, ruminal pH and concentrations of acetate and propionate did not differ due to oils compared with CK. Concentration of ruminal NH₃.N (13.65 vs. 17.39 mg/dL; p＜0.05) was higher due to oils compared with CK. However, Valeric acid, butyrate, total VFA, filter paper activities (7.58 vs. 5.58 U/mL; p＜0.05) and Lipase activities (204.26 vs. 151.71 U/L; p＜0.05) were significantly lower with oils supplementation compared with CK. No difference of LOC1 vs. LOC2 was observed for most of the above parameters.In experiment 3, compared with CK, cows fed oils had lower cellulolytic bacteria (3.25×10⁸ vs. 4.66×10⁸; p＜0.05) and protozoa (0.90×10⁵vs. 1.29×10⁵; p＜0.05) colony counts. Proteolytic bacteria (7.01×10⁸ vs. 6.08×10⁸; p＜0.05) counts, however, were higher in response to oils compared with CK. Supplemental fat had no effect on total viable bacteria and amylolytic bacteria colony counts compared with control diet (P＞0.05). No difference of LOC1 vs. LOC2 was observed for ruminal bacteria (except amylolytic bacteria) and protozoa colony counts. The counts of rumen microorganisms presented regular trend in different sampling time.In experiment 4, the method of total DNA extraction from ruminal content and the quantitative method of rumen microorganisms by real time PCR were improved. At the same time, the effects of supplemental 4% soybean oil and linseed oil of dry matter basis on ruminal A.lipolytica, biohydrogenation bacteria (B.fibrisolvens and R.albus )and cellulolytic bacteria (F.succinogenes and R. flavefaciens) DNA quantity were studied by real time PCR. The results showed that the DNA quantity of B.fibrisolvens, R.albus, F.succinogenes for cows fed supplemental fat diets significantly decreased (p＜0.05) compared with CK diet, fell 18%, 42%, 67% and 15%, respectively. DNA quantity of A.lipolytica and R. flavefaciens were no significant compared with CK diet (P＞0.05). The amount of B.fibrisolvens, F.succinogenes, and R. flavefaciens in ruminal fluid was substantially lower due to oil supplementation, primarily when LOC2 was fed. The inhibited effect of mixed linseed oil and soybean oil diet (LOC3) towards decreasing quantity of B.fibrisolven, F.succinogenes and R.flavefaciens was effectively improved.The results indicated that: (1) High-level fatty acid in feed mainly contained palmitic acid, stearic acid, oleic acid, linoleic acid and lnolenic acid. Nutrition and fatty acid trait in different feed showed difference. (2) Oils supplementation (4% of diet DM) to dairy cows affected ruminal fermentation parameters, microbe enzyme activities, cellulolytic bacteria and protozoa colony counts, but not affected total viable bacteria and amylolytic bacteria growth. (3) Supplemental 4% soybean oil and linseed oil significantly decreased the DNA quantity of B.fibrisolven, R.albus and F.succinogenes. In this context, results clearly showed that at the same level of supplementation linseed oil was more potent than soybean oil, leading to dramatic reductions in the quantity of B.fibrisolven, F.succinogenes, and R. flavefaciens. (4) Ruminal fermentation parameters, microbe enzyme activities and populations of ruminal bacteria also were affected by linseed oil and soybean oil, but the difference was not significant. (5) Detrimental effects of linoleic acid (soybean oil) and lnolenic acid (linseed oil) on ruminal microorganisms could partly explain the observed effects on ruminal fermentation parameters.