Livestock Foraging Behavior In Response To Sequence and Interactions Among Alkaloids, Tannins, and Saponins

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The influence of primary compounds (energy, protein, minerals, and vitamins) in animal nutrition and foraging behavior has been studied for years. The roles of secondary compounds (terpenes, alkaloids, and phenolic compounds) are equally important, yet they have been ignored until recently. Where secondary compounds were once considered toxic by-products of plant metabolism, we now know they are actively involved in plant and animal behavior, health, and productivity. Though often appreciated historically for their negative impacts on food intake and animal production, we are becoming increasingly aware of their beneficial roles in the health of plants, animals, and humans. When animals can ingest an array of plants that contain different kinds and amounts of secondary compounds, they can mix different foods in their diet to better use both primary and secondary compounds, enhancing their health and production, as well as economic and ecological characteristics of landscapes. Endophyte-infected tall fescue contains the alkaloids perlolidine, perloline, ergotamine, and ergovaline, which are all steroidal or protein-like in nature. Tannins and saponins have a high iv affinity for binding proteins and lipids in the gastro-intestinal tract of animals, and facilitating their excretion from the body. These findings suggest animals may increase their use of forages with alkaloids when they are also provided forages that contain tannins or saponins. The sequence in which forages with different secondary compounds are ingested may influence any potential interactions because different compounds have different residence times in the gastrointestinal tract. I tested the hypothesis that cattle and sheep foraging behavior is influenced by eating different combinations of forages containing secondary compounds in different sequences. In pen and pasture trials, I showed that 1) cattle grazing pastures of endophyte-infected tall fescue (TF) grazed more often on TF when first allowed to graze legumes containing either tannins or saponins, and they grazed TF much more when they first grazed legumes as opposed to the reverse sequence; 2) sheep fed basal diets high in the alkaloid ergotamine d tartrate (EDT) ate more when supplemented with food containing either tannins or saponins, but in contrast to the trials on pasture with cattle, their behavior was not dramatically influenced by sequence; 3) cattle fed fresh cut endophyte-infected tall fescue were not influenced by the addition of tannin to their drinking water, as tannins limited both water and forage intake; 4) sheep fed food containing EDT ate more when supplemented with food containing tannins or when given a choice of foods containing tannins or saponins, than sheep supplemented with food containing saponins or no additional secondary compound. Results from these studies suggest that secondary compounds interact with one another to influence foraging behavior, and that sequence of food ingestion can be influential when animals graze on pastures.