Fatty acids in rumen and meat of lambs fed with different condensed and hydrolysable tannin extracts

Five groups of lambs (n = 9 each) were used to test the effect of plant extracts rich in hydrolysable (HT) or condensed tannin (CT) on animal performance, fatty acid composition of rumen content and meat. The control group (CO) received a concentrate-based diet without tannins supplementation. The other groups received the same diet as the control lambs plus 4% chestnut (CH) and tara (TA) extracts as a source of HT and mimosa (MI) and gambier (GA) extracts as a source of CT. Dietary CH negatively affected animal performance. The rumen content of the different groups showed comparable levels of 18:3 c 9 c 12 c 15, 18:2 c 9 c 12, 18:2 c 9 t 11, 18:1 t 11 and 18:0, whereas 18:1 t 10 was greater in CO. Also, 18:1 t 10 tended to be lower in the rumen of HT than CT-fed lambs. These data were partially confirmed in meat, where CO showed a greater percentage of individual trans 18:1 fatty acids in comparison with tannins-fed groups. Our findings challenge some accepted generalizations on the use of tannins in ruminant diets as they were ineffective to favour the accumulation of dietary PUFA or healthy fatty acids of biohydrogenation origin in the rumen content and lamb meat, but suggest a general action of tannins on the whole biohydrogenation process.