Influence of Saponins and Tannins on Intake and Nutrient Digestion of Alkaloid-containing Foods

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Journal of the Science of Food and Agriculture

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asture-based livestock production systems typically emphasize low diversity of high-producing forages, abandoning locally adapted species of plants and animals in favor of new strains and breeds. 1 While these systems can be highly productive, they also require high inputs of fossil fuels. In contrast, natural landscapes, evolved in the absence of fossil-fuel inputs, are often diverse in taxonomy and chemistry with primary (nutrient) and secondary (pharmaceutical) compounds crucial in the nutrition and health of soil, plants, herbivores and people. Increasing plant biochemical diversity of pasture-based livestock production can reduce reliance on fertilizers, herbicides, and pesticides for plants, antibiotics and anti-helmintics for herbivores, and ultimately nutritional supplements and pharmaceuticals for people. 1–3 Herbivores evolved in complex environments ingesting arrays of foods of contrasting phytochemical characteristics. 4 Livestock obtain many benefits when they learn to eat diverse arrays of plants containing primary and secondary compounds. 1 For instance, lambs fed alfalfa (containing saponins) or birdsfoot trefoil (containing tannins) prior to eating alkaloid-containing grassessuchasendophyte-infectedtallfescueorreedscanarygrass consumed more dry matter (DM) and as a result ingested more nutrients than lambs fed only the alkaloid-containing grasses. These benefits may be due, in part, to tannins and saponins binding with and thus inactivating alkaloids in the gastrointestinal tract. Stable complexes form between alkaloids and tannins, and saponins bind to lipids such as cholesterol in the gastro-intestinal tract of animals, causing their excretion in the feces. However, in addition to these secondary compounds, forages also contain many different types of primary and other secondary compounds that also affect the degree to which saponins, tannins and alkaloids interact to influence intake and nutrient use.

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