Location: Forage-animal Production Research2018 Annual Report
Objective 1: Determine relationships of ergot alkaloids to receptors in animal tissues and subsequent effects on animal physiology, and the implications of these relationships on clearance from animal tissues. Subobjective 1.A. Evaluate the effect of ergot alkaloid exposure on vascular biogenic amine receptors. Subobjective 1.B. Characterize the interaction of isoflavones and their metabolites with ergot alkaloids on vasoactivity. Subobjective 1.C. Determine if there is ergovaline in bovine portal blood and determine site of absorption. Subobjective 1.D. Develop an oral endotoxin challenge model to determine the effects of fescue-derived alkaloid consumption on intestinal barrier function and innate immunity in cattle. Objective 2: Develop cost-effective management approaches to alleviate or mitigate the adverse effects of fescue toxicosis on animal physiology and well-being. Subobjective 2.A. Determine the impact of combining feeding soybean hulls (SBH) and red clover on weight gain performance of steers grazing toxic E+ tall fescue and mitigation of fescue toxicosis. Subobjective 2.B. Compare vasorelaxation between different sources of isoflavones for goats exhibiting ergot alkaloid-induced vasoconstriction. Subobjective 2.C. Determine if rumen tryptophan-utilizing bacteria will degrade ergot alkaloids in vivo. Subobjective 2.D. Assess phenotypic variation of cattle in their susceptibility to fescue toxicosis. Subobjective 2.E. Evaluate management approaches to cost effectively add value to cull cows and enhance ground beef quality. Subobjective 2.F. Comparison of supplemental selenium form to ameliorate physiological and gene expression stress response parameters in white blood cell (WBC), pituitary, adrenal, kidney, and liver of growing steers consuming E+ or E- tall fescue seed. Subobjective 2.G. Assess effects of animal temperament on fescue toxicosis-induced changes in animal growth and immunological responses. Objective 3: Determine the biological mechanisms used by certain plant secondary metabolites to function as antimicrobials in ruminants and non-ruminants, and assess their impact on animal health, performance, and well-being. Subobjective 3.A. Elucidate the antimicrobial mechanism of action of the red clover isoflavone, biochanin A, and determine antagonistic, additive or synergistic activity with other antimicrobials. Subobjective 3.B. Determine the effect of biochanin A on the rates of antibiotic resistance in ruminants. Subobjective 3.C. Determine the effect of clover phenolic compounds on nitrogen efficiency and weight gain in lambs. Subobjective 3.D. Evaluate spent brewer’s yeast as a carrier for hops secondary metabolites (prenylated phloroglucinols) in ruminant production.
Experiments will be conducted to determine mechanisms by which ergot alkaloids interact with receptors in animal tissues and affect their physiology. Saphenous veins collected from cattle at a local abattoir will be used to determine in vitro if inhibition of the phospholipase C and protein kinase C enzymes will alleviate ergot alkaloid induced vasoconstriction of smooth muscle. An in vitro experiment will ascertain if plant secondary metabolites, isoflavones, can mitigate the vasoactivity caused by ergot alkaloids. Endothelium cells from saphenous cells will also be exposed to ergot alkaloids to assess their effects on receptor signaling by ß-arrestin and G proteins. Catheters will be inserted in in the hepatic, portal and mesenteric veins of six rumen-fistulated steers to determine if rumen infused ergovaline is absorbed by the rumen and small intestines, or if the ergopeptine is degraded by rumen microbes. Field experiments will be conducted to evaluate management approaches to mitigate fescue toxicosis. Rumens will be infused with ergot alkaloids at a diet concentration of 0.8 ppm ergovaline and combined with either ground soybean meal, red clover, white clover, or a no isoflavone control. Cross sectional luminal areas of the right carotid artery of each goat will be measured by color Doppler ultrasonography. A grazing experiment with steers will evaluate the effects of feeding soybean hulls and overseeding toxic endophyte-infected tall fescue with red clover on animal weight gain and well-being. Four combinations of with and without the two treatments will be used as treatments to determine cost effectiveness of the treatments and mitigation of fescue toxicosis. Ear notches and phenotype data will be collected from multiple cow herds to detect polymorphisms of certain genes associated with fescue toxicosis and determine if these polymorphisms can be used to predict genetic tolerance to toxic ergot alkaloids. Three management approaches (soybean hulls, chemical seed head suppression, and red clover) to mitigate fescue toxicosis will be compared for adding body condition and weight to cull cows that graze toxic endophyte-infected tall fescue in either the spring or fall. To assess if selenium can ameliorate fescue toxicosis and if ergot alkaloids suppress immune response and alter gene expression in the liver, steers will be fed selenium depleted diets for 28 days and then switched to either inorganic selenium or an inorganic and organically bound selenium treatments for the remaining 98 days of the trial. The steers will also be fed either endophyte-infected or endophyte-free seed for the final 42 days. Jugular blood will be periodically collected and there will be staggered euthanasia of the steers for tissue collection. Effects of biochanin A on rate of antibiotic resistance will be determined by feeding rumen fistulated steers with either 0, 3 or 6 g biochanin A/day/steer and collecting rumen and fecal samples and using metagenomic DNA for quantitative PCR screening for antibiotic resistant genes.
Subobjective 1.A. - Evaluate the effect of ergot alkaloid exposure on vascular biogenic amine receptors. The first round of experiments has been completed with collections from 8 steers used to complete 2- and 24-hr incubations with equimolar concentrations of phospholipase C and protein kinase C inhibitors, ketanserin, or ergovaline. The contractile response data are currently being analyzed and samples are being processed for proteomic and genomic analysis of the signaling pathways associated with vascular smooth muscle contraction. Subobjective 1.C. Determine if there is ergovaline in bovine portal blood and determine site of absorption. (Harmon, Klotz) Preliminary experiments have been conducted with steers dosed with different levels of toxic endophyte-infected tall fescue seed to determine an appropriate ergovaline dosage. Samples of ruminal and portal vein blood from these preliminary experiments are being used to optimize analysis with mass spectrometry of blood ergovaline.
1. Using a blood vessel to evaluate a polymer. Ergot alkaloids produced by the fungal endophyte found in tall fescue are the toxins responsible for causing fescue toxicosis in grazing livestock. One strategy to mitigate or limit the effects of these toxins on livestock is to supplement with an adsorbent that prevents the absorption of the toxins from the digestive tract. Ergotamine, along with other ergot alkaloids, can influence vascular smooth contraction of bovine lateral saphenous veins. ARS scientists at Lexington, Kentucky in collaboration with University of Kentucky scientists evaluated the ergotamine binding activities of non-imprinted and molecularly imprinted polymers with a lateral saphenous vein bioassay to assess the effectiveness of the polymers. This study indicated that an incubation with either polymer reduced the contractile response to ergotamine in lateral saphenous veins in a dose dependent fashion with little evidence of differences between polymer type. However, further animal studies are required to assess the application of imprinted polymers as selective adsorbents of ergot alkaloids in feed. These findings will benefit research in support of the goal to mitigate fescue toxicosis with the validation of a polymer product that could be supplied in animal feed or mineral and ultimately benefit producers. This experiment demonstrated that ex vivo assessment of imprinted polymers ergot alkaloid binding capacity is possible with vascular bioassays.
2. Grazing two levels of ergovaline. Cattle that graze tall fescue pastures are exposed to fungally produced ergot alkaloids or toxins in the grass that cause vasoconstriction and result in fescue toxicosis. One strategy to mitigate the effects of these toxins to chemically suppress tall fescue seedhead production, where concentrations of the toxins are the highest, thereby reducing the amount of toxins in a pasture available for consumption. ARS scientists at Lexington, Kentucky evaluated the vasoactivity of serotonin receptors functionally involved in vasoconstriction in lateral saphenous veins biopsied from steers grazing non-toxic bermudagrass, standard endophyte-infected tall fescue untreated, and treated to suppress seedhead production. Chemical suppression of tall fescue seedhead production resulted in a lower toxin level that effected the activity of some serotonin receptor subtypes, but not other subtypes. This suggests that there is still some vascular adaptation in cattle to the toxins, even at lower pasture levels. The intake threshold of ergot alkaloids is of continual interest to livestock producers. This work will be of value to researchers interested in the physiological effects of ergot alkaloids in grazing animals and others in the field as a contribution to further defining pasture threshold levels of the toxins associated with fescue toxicosis.
3. Serotonin receptor profile of bovine rumen and small intestinal vasculature. The compounds that are responsible for causing fescue toxicosis are ergot alkaloids. Ergot alkaloids have been shown to cause vasoconstriction in the blood vessels supporting the gastrointestinal tract. This has been theorized to cause a reduction in nutrient uptake from the gut and contribute to the decreased productivity of growing cattle. ARS scientists at Lexington, Kentucky sought to identify what serotonin receptors are involved in ergot alkaloid-induced vasoconstriction in the rumen and small intestinal mesentery of cattle. Six different serotonin receptors were assessed for vasoactivity. It was found that serotonin receptor 2A was predominantly active across mesenteric and ruminal arteries and veins. None of the other receptors evaluated demonstrated contractile vasoactivity, however, serotonin 1D and 2B contributed to vasorelaxation in the mesenteric vein. These findings will benefit researchers as future studies are designed and conducted to further characterized the relationship between ergot alkaloids and serotonin receptors and how this contributes to fescue toxicosis.
4. Older, low-value hops could be used as a natural, growth-promoting feed additive for cattle. A type of bacteria in the gastrointestinal tracts of cattle and other ruminants causes protein to be wasted, which contributes to environmental contamination (ammonia) and causes the animals to gain less weight. These bacteria can be controlled with a natural compound in the hops plant, but hops are generally too expensive to use in cattle feed. However, there is a hops surplus and old hops go unused. USDA-ARS researchers in Lexington, Kentucky discovered that even after 5 years of storage, hops could control the wasteful bacteria in cattle. When the ammonia-producing bacteria are controlled, the animals gain weight more rapidly and efficiently. This result indicates that hops are a valuable byproduct feed additive even after they are considered too old to use in brewing.
5. A natural compound from red clover improved fiber fermentation by rumen bacteria from cattle. Rumen fiber fermentation is an important means of energy metabolism for grazing cattle. The clover compound, called an isoflavone, enhances fiber fermentation, which means that the animals can more efficiently utilize the fiber in the diet and receive more nutrients from high-fiber forages, like grass hay and grazed pastures. USDA-ARS scientists in Lexington, Kentucky demonstrated that this benefit can be achieved by grazing or feeding red clover hay without the need for extraction and concentration of the compound. Thus, red clover is a “functional feed” that small and large cattle farms can produce onsite or buy from a forage-grower. Legumes, like red clover, are already considered beneficial because they do not require nitrogen fertilizer and have health benefits for grazing animals. This result shows an additional benefit of red clover.
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Klotz, J.L., Aiken, G.E., Egert-McLean, A.M., Schrick, F., Chattopadhyay, N., Harmon, D.L. 2018. Effects of grazing different ergovaline concentrations on vasoactivity of bovine lateral saphenous vein. Journal of Animal Science. 6:3022–3030. doi: 10.1093/jas/sky163.
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Harlow, B.E., Flythe, M.D., Kagan, I., Aiken, G.E. 2016. Biochanin A (an isoflavone produced by red clover) promotes weight gain of steers grazed in mixed grass pastures and fed dried-distillers grains. Crop Science. 57:506-514.
Harlow, B.E., Aiken, G.E., Flythe, M.D. 2017. Biochanin A improves fiber fermentation by cellulolytic bacteria. Journal of Applied Microbiology. 124(1):58-66.
Puchala, R., LeShure, S., Gipson, T.A., Tesfai, K., Flythe, M.D., Goetsch, A.L. 2018. Effects of different levels of lespedeza and supplementation with monensin, coconut oil, or soybean oil on ruminal methane emission by mature Boer goat wethers after different lengths of feeding. Journal of Applied Animal Research. 46(1): 1127-1136.
Zou, J., Chassaing, B., Singh, V., Pellizzon, M., Ulman, E., Ricci, M., Flythe, M.D., Vijay-Kumar, M., Gewirtz, A.T. 2018. Fiber-mediated nourishment of gut microbiota protects against diet-induced obesity by restoring IL-22-mediated colonic health. Cell Host and Microbe. 23:41-53.
Klotz, J.L., McDowell, K.J. 2017. Tall fescue ergot alkaloids are vasoactive in equine vasculature. Journal of Animal Science. 95(11):5151-5160.
Snider, M.A., Harmon, D.L., Matthews, J.C., Klotz, J.L. 2018. Pharmacologic assessment of bovine ruminal and mesenteric vascular serotonin receptor populations. Journal of Animal Science. 96(4):1570-1578.
Miller, D.M., Redmond, C.T., Flythe, M.D., Potter, D.A. 2017. Evaluating a novel endophytic grass for suppressing invertebrates that contribute to bird strike risk at airports. Crop, Forage & Turfgrass Management. 3(1):1-11.
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