Use of tannins to modify ruminal biohydrogenation in sheep. 2) Effects on in vitro fatty acid composition of rumen digesta

Comunicación presentada en el 14th International Seminar of the FAO-CIHEAM Sub-Network on Sheep and Goat Nutrition: Feeding and management strategies to improve livestock productivity, welfare and product quality under climate change, p. S1-O-02-2. 15-18 de mayo de 2012. Túnez (Túnez).Supplementing the diet of ruminants with tannins has been suggested as a strategy to modulate ruminal biohydrogenation (BH) of dietary polyunsaturated fatty acids (FA) and enhance the accumulation of vaccenic acid (VA) due to an inhibition of the last step of BH. The ultimate goal of this strategy is to increase the content of some bioactive FA (such as CLA or VA) in the ruminant products. This experiment was conducted in sheep to study the effect of the addition of tannins to a total mixed ration supplemented with 2% DM of sunflower oil on ruminal BH. The assay was carried out in vitro using batch cultures of rumen microorganisms. Four commercial extracts of tannins [2 hydrolysable (HT: chestnut and oak) and 2 condensed (CT: quebracho and grape) tannins] × 2 doses of each one (2 and 5% DM) ) were added to the supplemented diet. After 24 h incubations, none of the four tannin extracts and none of the two doses tested were able to modify the rumen contents of total CLA, VA or stearic acid. However, some increases were detected in the concentration of linolenic, linoleic and oleic acids, which may suggest a general inhibition of the ruminal BH rather than a specific inhibition of the last step. Most significant results were observed with HT and at 5%. Overall, the results would not allow to recommend this strategy to modulate ruminal BH and improve the nutritional quality of the ruminant products.Peer reviewe