Effect of the Level of Carbohydrates on Bio-hydrogenation and CLA Production by Rumen Bacteria When Incubated with Soybean Oil or Flaxseed Oil In vitro

Abstract

An in vitro study was conducted to examine the effect of addition level of carbohydrates on fermentation characteristics, and bio-hydrogenation of unsaturated fatty acids by mixed rumen bacteria when incubated with soybean oil or flaxseed oil. Four levels(0%, 0.3%, 0.6% and 0.9%, w/v) of the mixed carbohydrates(glucose, cellobiose, soluble starch, 1:1:1, in weight basis) and oil sources(soybean or flaxseed oil, 60 mg in 150 ml culture solution) were added to the mixed solution of strained rumen fluid with artificial saliva(1:4, v/v), and incubated anaerobically for 12 hours at 39 . pH and ammonia-N concentration were lower by increasing the substrate levels at all incubation periods(P<0.05 P<0.001). The propionate proportion increased(P<0.001), but acetic acid and butyric acid decreased(P<0.001) with the substrate level at 6 and 12 h incubations. Oil sources did not influence the proportions of individual VFA. At the end of incubation, the proportions of C18:0 (P<0.01), C18:1 (P<0.001) and trans-11C-18:1 (P<0.01) were reduced but those of C18:2 (P<0.001) and C18:3 (P<0.01) were enhanced by the addition of flaxseed oil compared to addition of soybean oil. The proportions of C18:0 and total CLA were reduced(P<0.01) but those of trans-11-C18: (P<0.05) and C18:2 (P<0.01) were increased with the substrate level when incubated with soybean oil or flaxseed oil. There were interactions(P<0.05) in the proportions of C18:1, C18:2 and C18:3 (P<0.01) between oil source and substrate level. The proportions of cis-9, trans-11-CLA and trans-10, cis-12-CLA tended to reduce with substrate level, although there was no significant difference between treatments.