Tannins in Ruminant Nutrition: Impact on Animal Performance and Quality of Edible Products

Tannins are widespread throughout the plant kingdom, occurring as hydrolysable and condensed tannins and at different levels in several animal feeding sources. Recent years have seen an increasing interest in the use of tannin-rich plants and plant extracts in ruminant diets for improving the quality of their edible products. Some results show that this strategy is effective in improving the fatty acid profile of meat and milk, increasing the level of health-beneficial fatty acids as well as enhancing the oxidative stability of the products. However, the use of tannin-rich feed in animal diets requires great care, due to its possible detrimental effects on animal performance and induction of metabolic disorders. Although promising, the results of studies on the effects of tannins on animal performance and quality of their products are still controversial, probably depending on type and chemical structure of tannins, amount ingested, composition of diet, and species of animal. In this chapter, the current knowledge regarding the effect of dietary tannins on animal performance and the quality of their products (meat and milk), particularly on the fatty acid profile, oxidative stability, and organoleptic properties, is reviewed. The tannin chemistry diversity and its occurrence in ruminant diets, as well as its beneficial and adverse effects on ruminants, will be briefly reviewed, and aspects related to oral cavity physiology, saliva production/composition, and postingestive effects will also be discussed.

Efeito do teor proteico da dieta na digestibilidade da bolota em porcos alentejanos

O objectivo do presente ensaio é avaliar o efeito do teor proteico da dieta na digestibilidade da bolota em porcos Alentejanos. Para tal, nove animais foram seccionados e colocados em caixas metabólicas onde as dietas foram distribuídas aleatoriamente, segundo o Modelo de Quadrado Latino 3 x 3. O ensaio in vivo foi assim dividido em três períodos, durante os quais se recolheram amostras de alimento, refugos fezes e urina para posterior análise em laboratório. Foi determinada a composição química do alimento e calculada a digestibilidade e balanço de azoto dos três tratamentos. Também foi determinado o conteúdo em compostos fenólicos e taninos da bolota pelo método do Folin­ Ciocalteu, taninos condensados pelo método do Butanol-HCl e a capacidade complexante dos taninos pelo método da Difusão Radial. Devido à reduzida capacidade de os taninos complexarem as proteínas e à baixa ingestão da luzerna não foi possível verificar diferenças na proteína ingerida entre os tratamentos testados. ABSTRACT; The aim of present experiment is to evaluate the effect of protein content in diet digestibility of oak acorn in Alentejano pigs. For that, nine animals were selected and housed in metabolic cages where diets were given randomly, in a Latin Square model3 x 3. The in vivo experiment was divided in three periods, during which were collected feed, refusals, feces and urine samples for subsequent laboratory analyses. Chemical feed composition was determinate and calculated the digestibility and nitrogen balance in three treatments. It was also determinate the amount of phenolic compounds and tannins on oak acorn by Folin-Ciocalteu assay, condensed tannins by Butanol-HCl assay and the availability to form complex with protein by Radial Diffusion assay. It was observed a reduced availability of tannins to bind proteins and a low Lucerne intake, so it wasn't possible to verify differences on protein intake, between tested treatments.

Propolis components accountable for bactericidal accomplishment and antibiofilm activity

This study aimed at evaluating antimicrobial and antibiofilm activity of phenolic compounds present in propolis ethanol extracts (PEE). Seventy per cent ethanol extracts from seven types of propolis, one Green, two Red and four Brown collected in four Brazilian States were prepared and total phenolics, flavonoids, tannins and anthocyanins were assessed by high-performance liquid chromatography (HPLC). Minimum bactericidal concentration (MBC) and inhibitor effect on Staphylococcus aureus biofilm formation and capacity to disrupt established biofilms were assessed towards eight S. aureus isolates from milk of small ruminants with mastitis, one methicillin-resistant S. aureus (MRSA) and S. aureus ATCC 25923. To evaluate different propolis components accountability for bactericidal accomplishment and antibiofilm activity, the results were analysed by the non-parametric Spearman coefficient. Results of phenolic compounds were 216,21 to 312,08 gallic acid milligram equivalent per extract gram (mg EGA/g) of total phenolics, 55,08 to 140,6 quercetin milligram equivalent per extract gram (mg EQ/g) of flavonoids, 118,51 to 3766,16 catechin milligram equivalent per extract gram (mg EC/g) of tannins and 1,03 to 8,39 milligram per extract gram (mg/g) of anthocyanins. Red1 and Red2 showed higher tannin contents, while Red2 exhibited superior amount of anthocyanins and total phenolics. Brown3 presented higher flavonoid quantity. Green, Red1 and Red2 PEE showed the lowest levels of flavonoids, but the higher antimicrobial activity. Most PEE exhibit bactericidal activity at a concentration of 1.6 mg/mL. Brown4 PEE showed the worst capacity to inhibit S. aureus. Green PEE showed to be the most efficient in both preventing and disrupting biofilm. All PEE studied exhibited a better inhibitory activity prior-to than post-biofilm formation. According to non-parametric Spearman correlation analysis, there seems to be a significant negative correlation between the ability to disrupt biofilm and both tannins and anthocyanins contents.

Oral food perception and polyphenol-rich foods acceptance - the importance of knowing individuals saliva characteristics for promoting consumption

Polyphenols are widely present in fruits, vegetables, cereals and beverages. Their study gained scientific interest because of their beneficial effects on health. Although there is currently no official dietary recommendation for polyphenol intake, health professionals recommend the consumption of 5-8 daily portions of fruits and vegetables. This is not always achieved and, despite possible causes associated to practical schedule difficulties, the aversive bitter and astringent sensations associated to polyphenols may also lead to avoidance. As such, a better understanding on mechanisms responsible for differences among people, in polyphenol oral perception, is needed for promoting healthier choices. Saliva has been linked to polyphenol consumption. We have previously observed, in animal models, changes in salivary proteome induced by tannin-enriched diets. Moreover, differences in astringency perception were attributed to differences in salivary protein composition. In a recent experiment, we observed differences among individuals with dissimilar tannic-acid perception: people with high sensitivity for the oral sensations elicited by tannins have higher amounts of salivary cystatins and lower capacity to maintain their levels after tannic-acid ingestion. Additionally, and similarly to previous studies, salivary amylase was observed to be involved in tannin perception. In this presentation, oral cavity characteristics influencing the perception of polyphenol-containing foods will be discussed.