Location: Forage-animal Production Research2019 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. Enzyme inhibition myograph experiments have been completed. Proteomic receptor analysis has been completed and transcriptomic analysis of samples in ongoing. Beta-arrestin recruitment cell culture experiments have been completed. Subobjective 1.B - Characterize the interaction of isoflavones and their metabolites with ergot alkaloids on vasoactivity. The primary bovine endothelial cell line has been isolated from 5 Holstein steers. Subobjective 1.C. - Determine if there is ergovaline in bovine portal blood and determine site of absorption. A preliminary study was conducted and significant hurdles were encountered in the establishment of an accurate and precise extraction of ergovaline from whole blood. This has been addressed and the samples from the preliminary study are currently being analyzed. 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. Steers were cannulated and dosed with various levels of LPS into the abomasum. Subobjective 2.A. - Determine the impact of combining feeding soybean hulls 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. This study has been completed and data is being analyzed. Subobjective 2.C. - Determine if rumen tryptophan-utilizing bacteria will degrade ergot alkaloids in vivo. Fistulated steers are currently being used in feeding trials to collect samples to assess ergot alkaloid degradation. Subobjective 2.D. - Assess phenotypic variation of cattle in their susceptibility to fescue toxicosis. Phenotypes and samples for genotyping continue to be collected. Subobjective 2.F. - Comparison of supplemental selenium form to ameliorate physiological and gene expression stress responses parameters in white blood cell, pituitary, adrenal, kidney, and liver of growing steers consuming E+ or E- tall fescue seed. Study is currently in progress. Steers are currently on pasture and selenium treatments with sample collections scheduled for early fall. Subobjective 2.G. - Assess effects of animal temperament on fescue toxicosis-induced changes in animal growth and immunological responses. All cattle for both the confinement as pasture experiment have been selected and sorted based on temperament. 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. These experiments addressing the minimum inhibitory concentrations with biochanin A and antibiotics are ongoing. Subobjective 3.B. - Determine the effect of biochanin A on the rates of antibiotic resistance in ruminants. A biochanin A feeding trial has been conducted. Subobjective 3.C. - Determine the effect of clover phenolic compounds on nitrogen efficiency and weight gain in lambs. Work to isolate bacteria and perform taxonomic characterization and assess biochanin A susceptibilities is ongoing.
1. Ergot alkaloids cause reduced fetal growth. Livestock that graze toxic endophyte-infected tall fescue suffer from impaired reproduction that reduces the profitability of forage-based livestock operations. ARS scientists at Lexington, Kentucky, in collaboration with Clemson University scientists conducted a study that demonstrated that ewes exposed to ergot alkaloids during pregnancy had significantly smaller lambs. From these same ewes was also shown that ergot alkaloid exposure during gestation reduces uterine and umbilical vasoactivity. This leads to decreased blood flow and can contribute to the observed reduction in fetal growth. This work has clearly characterized the gestational problems associated with ergot alkaloids found in tall fescue. This characterization will be important to research focusing on the development mitigation strategies associated with the reproductive issues associated with ergot alkaloid exposure.
2. Ergovaline binds with serotonin receptors. Ergovaline is found in the highest percentages of all of the toxic ergot alkaloids produced by the fungal endophyte found in tall fescue. Livestock that consume ergovaline have been shown to have a reduced vascular capacity to respond to serotonin. ARS scientists at Lexington, Kentucky, in collaboration with University of Kentucky scientists looked specifically at the relationship between ergovaline and serotonin receptor 2A that is associated with vascular smooth muscle contraction. Following ergovaline exposure, the blood vessel response to a selective agonist for serotonin 2A was inversely proportional to the concentration of ergovaline exposure. Ergovaline can act as a partial agonist and an antagonist with the serotonin receptor 2A resulting in prolonged vasoconstriction in bovine vasculature. This finding is critical in understanding how these toxins interact with mammalian receptors and is important to researchers seeking to further the work in developing a solution based product.
3. Corn improves digestibility of tall fescue. There is a lack of information about the effect of different sources, levels, and the mixtures of energy supplements commonly fed to cattle grazing tall fescue. ARS scientists at Lexington, Kentucky, in collaboration with University of Kentucky scientists looked at in vitro fermentation of fescue hay, corn, corn gluten feed, soybean hulls and combinations of the supplements. All energy supplemented flasks had elevated methane production. Corn grain supplementation at low levels (< 0.25% BW) can improve fescue utilization by increasing digestibility and could improve beef cattle productivity. This finding is important to cattle producers that want to supplement energy to grazing herds.
4. Polychlorinated biphenyls alter gut bacteria. Polychlorinated biphenyls are an environmental contaminant that can negatively impact the health of animals and humans. USDA scientists in Lexington, Kentucky, in collaboration with University of Kentucky scientists determined that the polychlorinated biphenyl called PCB126, alters the gut metabolism through antimicrobial activity on the cell membrane of sensitive gut bacteria. This is the first evidence that polychlorinated biphenyls can influence metabolism by the gut microbiota, which will be important information in developing dietary interventions to aid people and animals exposed to polychlorinated biphenyls.
5. Giving birth decreases beneficial bacteria in horses. Mares go through a variety of physiological changes from pregnancy to weening the foal. University of Kentucky and USDA scientists in Lexington, Kentucky, showed that the number of cellulose-using bacteria in the hindgut of a mare decreases when the foal is born. Given that cellulose is a major energy substrate for horses, further work is required to understand if the disappearance of these beneficial bacteria have impacts on the mare. This is important to horse breeders that deal with this reproductive aspect of equine production.
Trotta, R.J., Klotz, J.L., Harmon, D.L. 2018. Effects of source and level of dietary energy supplementation on in vitro digestibility and methane production from tall fescue-based diets. Animal Feed Science And Technology. 242:41-47. https://doi.org/10.1016/j.anifeedsci.2018.05.010.
Melchior, E.A., Smith, J.K., Schneider, L.G., Mulliniks, J.T., Bates, G.E., Flythe, M.D., Klotz, J.L., Ji, H., Goodman, J.P., Lee, A.R., Caldwell, J.M., Myer, P.R. 2018. Effects of endophyte-infected tall fescue seed and red clover isoflavones on rumen microbial populations and physiological parameters of beef cattle. Translational Animal Science. 3:316-328. https://doi.org/10.1093/tas/txy147.
Melchior, E.A., Smith, J.K., Schneider, L.G., Mulliniks, J.T., Bates, G.E., McFarlane, Z.D., Flythe, M.D., Klotz, J.L., Goodman, J.P., Ji, H., Meyer, P.R. 2018. Effects of red clover isoflavones on tall fescue seed fermentation and microbial populations in vitro. Animal Feed Science And Technology. 13(10): e0201866. https://doi.org/10.1371/journal.pone.0201866.
Trotta, R.J., Harmon, D.L., Klotz, J.L. 2018. Interaction of ergovaline with serotonin receptor 5-HT2A in bovine ruminal and mesenteric vasculature. Journal of Animal Science. 96:4912-4922. https://doi.org/10.1093/jas/sky346.
Klotz, J.L., Britt, J.L., Miller, M.F., Snider, M.A., Aiken, G.E., Long, N.M., Pratt, S.L., Andrae, J.G., Duckett, S.K. 2019. Ergot alkaloid exposure during gestation alters: II. Uterine and umbilical artery vasoactivity. Journal of Animal Science. 97(4):1891-1902.
Britt, J.L., Greene, M.A., Bridges, Jr., W.C., Klotz, J.L., Aiken, G.E., Andrae, J.G., Pratt, S.L., Long, N.M., Schrick, F., Strickland, J.R., Wilbanks, S.A., Miller, Jr., M.F., Koch, B.M., Duckett, S.K. 2019. Ergot alkaloid exposure during gestation alters: I. Maternal characteristics and placental development. Journal of Animal Science. 97(4):1874-1890. https://doi.org/10.1093/jas/skz068.
Greene, M.A., Britt, J.L., Powell, R., Feltus, F.A., Bridges, Jr., W.C., Bruce, T., Klotz, J.L., Miller, M.F., Duckett, S.K. 2019. Ergot alkaloid exposure during gestation alters: III. Fetal growth, muscle fiber development, and miRNA transcriptome. Journal of Animal Science. https://doi.org/10.1093/jas/skz153.