The effect of inclusion of plant extracts to ruminal fluid on conjugated linoleic acid (CLA) isomers formation and fermentation parameters was evaluated. Initially, fifteen plant extracts at two levels (1 and 2 mg/mL buffered rumen fluid; BRF) were incubated with BRF and substrate (hay and concentrate at 50:50) at 39ºCfor 24 h, in a completely randomized block design. In second experiment four promising plant extract on CLA plus vaccenic acid (VA) formation were tested for their influence on basal parameters of rumen fermentation. The first study revealed that extracts of Azadiracta indica, Allium sativum, Cuminum cyminum at lower level (1mg/mL) and extracts of Terminalia chebula at higher level (2mg/mL) enhanced CLA isomers formation 45.56, 41.54, 51.09 and 15.54%, respectively, and VA concentration 10.97, 10.82, 14.93 and 29.61%, respectively, in ruminal fluid when compared with control (P<0.05). Second experiment documented selected plant extract did not impair nutrient fermentation. However, addition of extract of C. cyminum to ruminal fluid enhanced partitioning factor (P=0.054) and increased digestibility of nutrient (P<0.05) . Furthermore, polyunsaturated fatty acid concentration was higher when ruminal fluid was incubated with extract of C. cyminum, (P=0.049). In conclusion, extract of Azadiracta indica, Allium sativum, Cuminum cyminum and Terminalia chebula modulate ruminal biohydrogenation and augmente CLA isomers, their precursors and VA concentration without negative effect on other rumen parameters. However, Cuminum cyminum improved pattern of nutrient fermentation and can be consider as valuable supplements in ruminant nutrition to enhance the healthiness of ruminant meat and milk.

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