A Spoonful of Legumes Helps the Alkaloids Go Down
In the summer of 2007, graduate student, Tiffanny Lyman, investigated the impact of forage sequence on intake of tall fescue, reed canarygrass (two grasses that contain alkaloids) and birdsfoot trefoil and alfalfa (legumes that contain tannins and saponins). Lyman found that when cattle grazed fescue followed by trefoil and alfalfa, they spent less of their time ( from 40% to 15%) actively foraging on tall fescue from 40% to 15%. When the sequence was reversed, the same group of cattle increased their time spent foraging on fescue from 15% to 50%. A similar trend was found with reed canarygrass and trefoil and alfalfa. Sequence did not affect the amount of time spent grazing legumes but cattle that grazed fescue preferred trefoil and those that grazed canarygrass preferred alfalfa.
In 2008, Lyman ran two follow-up studies to further investigate how sequence and legume species affect time spent grazing endophyte-infected tall fescue (TF) by cattle. She used the following forages high-alkaloid TF, high-saponin alfalfa and birdsfoot trefoil (BFT) that contains tannins.
In the first study, one group of cattle grazed TF followed by BFT while the other group received the reverse order. Cattle grazing TF first were erratic in amount of time spent grazing TF, up one day and down the next. Grazing patterns were similar to intake patterns of animals eating a nutritious, toxic food. Whereas cattle grazing BFT first, spent more time grazing TF and did not exhibit wild swings in amount of time spent grazing TF.
In the second study, one group of cattle grazed alfalfa followed by TF, the other group foraged in the reverse sequence. Cattle grazing alfalfa first spent 58% of their time grazing TF while cattle eating TF first spent 28% of their time grazing TF. Cattle turned out on TF first, often laid down and refused to graze TF (photo above right) but were willing to graze alfalfa later in the morning (photo right). Both groups of cattle increased intake of TF during the trial regardless of when they grazed alfalfa.
Lyman’s results demonstrate that forage intake is not only dependent on what an animal eats but also when it eats a plant. Furthermore, planting the correct mix of forages may improve intake of endophyte-infected grasses.