Author
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Aiken, Glen |
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Submitted to: Cow Country News
Publication Type: Popular Publication Publication Acceptance Date: 3/31/2015 Publication Date: 4/1/2015 Citation: Aiken, G.E. 2015. From the Lab Bench: Can cattle meet their nutrient needs on toxic tall fescue pasture?. Cow Country News. Pgs. 48-50. Interpretive Summary: Losses in cattle production during the summer have been related to severe heat stress caused by fescue toxicosis. Ergot alkaloids produced by the fungal endophyte in tall fescue which reduces blood flow to the limbs, head region, and tails where body heat contained in blood is dissipated. We know this buildup of body heat and fever can dramatically decrease forage consumption and cause the animal to lose body weight and condition, but what about blood flow to other parts of the body, such as the rumen and midgut regions where nutrients are digested and absorbed into the blood system? This possible consequence was studied by Jimmy Klotz, a ruminant physiologist with the USDA-ARS Forage-Animal Production Research Unit, and Dave Harmon, a ruminant nutritionist with the University of Kentucky’s Animal and Food Sciences Department, and a group of graduate students. This research group found that blood flow to the rumen and gut regions are decreased by 50% in cattle consuming toxic endophyte-infected tall fescue, which causes reduced absorption of nutrients by the rumen. However, it was further determined that body weight and condition losses for cattle grazing tall fescue in the spring and summer are related more to reductions in forage intake than to losses in nutrient absorption. This research improves our understanding of the implications of reduced blood flow in cattle grazing toxic tall fescue and will be useful to ruminant nutritionists and physiologists in developing technologies to alleviate or mitigate the adverse effects of fescue toxicosis. Technical Abstract: A column is written to provide information on nutrient utilization by cattle grazing toxic endophyte-infected tall fescue. We have considerable knowledge and understanding of ergot alkaloid-induced constriction of blood flow to peripheral tissues, but what about blood flow to other parts of the body, such as the rumen and midgut regions where nutrients are digested and absorbed into the blood system? This possible consequence was studied by Jimmy Klotz, a ruminant physiologist with the USDA-ARS Forage-Animal Production Research Unit, and Dave Harmon, a ruminant nutritionist with the University of Kentucky’s Animal and Food Sciences Department, and a group of graduate students. Peer reviewed publications from in vitro and in vivo experiments have shown: 1) mysenteric arteries and veins vasoconstrict by as much as 50% significant when exposed to the ergot alkaloid, which is associated with a reduction in ruminal absorption of volatile fatty acids, and 2) losses in body weight and condition by cattle grazing toxic tall fescue pastures during the late spring and summer are related more to reductions in dry matter intake than from declines in gut absorption of nutrients. This research provided a better understanding of why cattle can have such a rapid loss in body weight and condition as grazing continues into the hot summer months on fescue pastures. |
