Abstract
Simple SummaryTannins are known as water-soluble polyphenols with the ability to form complexes with macromolecules of dietary and endogenous origin. Thus, they are becoming increasingly popular among scientists as an invaluable “tool” for targeted modification of digestive processes in the rumen. The aim of the study was to compare the effect of tannins of various origin—oak bark extract (natural) vs. tannic acid (synthetic) on the fatty acid composition in the ruminal fluid of sheep. It was shown that both sampling time and animal diet had a significant effect on tested parameters, but this effect was varied. The addition of tannic acid to sheep diet had a greater influence on the fatty acid profile in the rumen than oak bark extract. Differences in the effects of tested additives may arise from the presence of various types of tannins in oak bark extract. Increased concentrations of C18:2 c9c12 and C18:3 c9c12c15 in sheep fed diet with tannic acid addition may suggest inhibition of the initial stage of fatty acid biohydrogenation. These promising results may increase knowledge about the action of such compounds on lipid metabolism in the rumen, and provide the basis for further research on health-promoting properties of ruminant products.The aim of the study was to compare two sources of tannins on fatty acids (FA) composition in rumen. Treatments were (g tannins/kg diet as-feed-basis) as follows: (1) no supplemental tannin addition (CON), (2) addition of 13 g of oak bark extract (OAK), and (3) 4 g of tannic acid (TAN). The basal diet contained 55:45 forage to concentrate ratio. Net consumption of tannins (g/d) was 4 g for both tannins sources. The study was performed on three Polish Mountain ewes fitted with rumen cannulas, and was divided into three experimental periods (I, II, and III). Both sampling time and animal diet had a significant effect on FA profile in the rumen fluid. In general, FA concentrations were higher before feeding in comparison to samples collected 2 and 4 h after feeding. In terms of dietary effect, it was shown that TAN addition had a greater influence on FA profile in the ruminal fluid than the OAK diet. Briefly, in the TAN group significantly increased concentrations of C18:2 c9c12 (linoleic acid, LA) 8 h after feeding (vs. control, CON and OAK), C18:3 c9c12c15 (α-linolenic acid, LNA) 4 h after feeding (vs. OAK), C20:3 n-6 before feeding (vs. CON), C20:4 before feeding (vs. CON and OAK) and 8 h after feeding (vs. OAK) were recorded. In contrast, OAK addition significantly reduced C20:3 n-6 concentration 2 h after feeding (vs. CON). In conclusion, increased concentrations of both LA and LNA in the rumen indicated that supplemental tannic acid may inhibit the initial stage of FA biohydrogenation in the rumen.
Highlights
IntroductionTannins are a group of water-soluble polyphenols with different chemical structure (mainly of condensed and hydrolysable types) and reactivity, commonly found in the creativecommons.org/licenses/by/ 4.0/)
The animals from the oak bark extract (OAK) and tannic acid (TAN) groups received a slightly higher amount of dry matter (DM) as compared to the CON sheep, which was caused by the presence of the tested additives
We demonstrated that the TAN diet had a greater influence on fatty acids (FA) profile in the ruminal fluid than the OAK diet
Summary
Tannins are a group of water-soluble polyphenols with different chemical structure (mainly of condensed and hydrolysable types) and reactivity, commonly found in the creativecommons.org/licenses/by/ 4.0/). They exhibit unique properties, including the ability to form complexes mainly with proteins of various origin (dietary, endogenous, microbiological), and to a lesser extent with other components, such as metal ions and carbohydrates [2,3]. The low pH in the abomasum (below 3.5) promotes the release of complexes with tannins, making it possible to digest the dietary protein and increase absorption of amino acids in the small intestine [5]. Condensed tannins appear to pass intact through the digestive tract. Those tannins with low polymerization (such as dimers) can be absorbed and enter the bloodstream [6]. Literature data proved that hydrolysable tannins can be degraded by microbial activity [5,7], and their intermediate metabolites (e.g., gallic acid) are found in the urine [8]
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