Abstract
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, liver 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. One-way ANOVA was used to assess the overall effect of dietary treatments, tannins supplementation (CO vs. CH+TA+MI+GA) and the effect of tannin type (HT vs. CT: CH+TA vs. MI+GA) on animal performance, rumen content, liver and intramuscular FA. Dietary CH negatively affected animal performance. The rumen content of the different groups showed similar levels of 18:3 c9c12c15, 18:2 c9c12, 18:2 c9t11, 18:1 t11 and 18:0, whereas 18:1 t10 was greater in CO. Also, 18:1 t10 tended to be lower in the rumen of HT than CT-fed lambs. These data were partially confirmed in liver and 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 generalized influence on BH rather than on specific steps.
Highlights
Tannins are water-soluble phenolic compounds that are produced by plants in response to external stressor factors [1], Chemically, tannins can be broadly classified into hydrolysable (HT) and condensed (CT)
In a preceding paper [19], we characterised the ruminal fermentation and microbiome in lambs supplemented with four different tannin extracts rich in hydrolysable or condensed tannins and we found that in a long-term feeding trial the extracts did not compromise ruminal fermentation, but showed specific antimicrobial activity against rumen microflora, which may elicit differences on fatty acids metabolism and on PUFA biohydrogenation
The supplementation of tannins in the diet of lambs did not affect animal performance (P > 0.05), except for dry matter intake (DMI; P = 0.048), which was greater in the control group (CO) group than CH+TA+GA+MI
Summary
Tannins are water-soluble phenolic compounds that are produced by plants in response to external stressor factors [1], Chemically, tannins can be broadly classified into hydrolysable (HT) and condensed (CT). Hydrolysable tannins are polymers of gallic or ellagic acid associated by the mean of an ester bond with a polyhydroxylated core, whereas CT are represented by flavan-3-ol polymers [2]. Condensed and hydrolysable tannins on lamb fatty acid metabolism
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