Effects of vitamin E on the concentration of conjugated linoleic acids and accumulation of intermediates of ruminal biohydrogenation in vitro

The aim of this study was to investigate effects of vitamin E (Vit. E) addition to high soybean oil diets on the concentration of conjugated linoleic acids (CLA) and accumulation of biohydrogenation intermediates in mature goat rumen fluid using an in vitro batch culture technique. Rumen fluid collected from six fistulated mature goats was incubated for 24 h with addition of Vit. E at different concentrations [0 (control), 0.5, 1.0 and 2.0 mg/80 ml] in triplicate. Results indicate that acetate, total volatile fatty acid (VFA), as well as the ratio of acetate to propionate, increased at a decreasing rate (linearly P < 0.01 and quadratic P < 0.05) with increased Vit. E supplementation, whereas the concentration of butyrate linearly (P < 0.001) decreased. Vit. E had no effect on pH, ammonia-N, and total gas production. However, Vit. E linearly (P < 0.001) decreased cis-9, trans-11 CLA concentration, linearly (P = 0.002) increased trans-11 C18:1 and concentration of trans-10 C18:1 was the lowest at intermediate addition levels of Vit. E (quadratic P < 0.001). Concentrations of linoleic acid and linolenic acid were both linearly (P < 0.05) decreased at a decreasing rate with increased Vit. E addition. Vit. E linearly (P = 0.001) decreased the oleic acid concentration, whereas that of stearic acid was linearly (P < 0.001) increased. Results demonstrate that Vit. E supplementation affected ruminal fermentation parameters, particularly the concentration of conjugated linoleic acids and accumulation of intermediates of ruminal biohydrogenation in the ruminal fluid. The mechanism by which Vit. E may alter biohydrogenation is unclear, but the modification of rumen microbial populations/dynamics and consequent fatty acid hydration might be involved.