Modulation of in vitro rumen biohydrogenation by Cistus ladanifer tannins compared with other tannin sources

BACKGROUND Tannins are polyphenolic compounds able to modify the ruminal biohydrogenation ( BH ) of unsaturated fatty acids, but their activity may vary among different tannin sources. The effect of rockrose ( Cistus ladanifer ) on BH has never been compared with other more common tannin sources. Tannin extracts (100 g kg −1 substrate dry matter) from chestnut ( CH ), quebracho ( QB ), grape seed ( GS ) and rockrose ( CL ) were incubated in vitro for 6 h with ruminal fluid using as substrate a feed containing 60 g kg −1 of sunflower oil. A control treatment with no added tannins was also included. RESULTS Compared with the control, GS and CL , but not CH and QB , increased ( P < 0.05) the disappearance of c 9, c 12‐18:2 with a consequent larger production of c 9, t 11‐18:2 and t 11‐18:1. However, no differences among treatments ( P > 0.05) were observed for the disappearance of c 9‐18:1 and c 9, c 12, c 15‐18:3. The production of 18:0 was not different ( P > 0.05) among treatments, although its proportion in the total BH products was lower ( P < 0.05) for GS than for the other treatments. CONCLUSION Condensed tannins from GS and, to a lesser extent, from CL stimulate the first steps of BH , without a clear inhibition of 18:0 production. © 2016 Society of Chemical Industry