Location: Forage-animal Production Research
2020 Annual Report
Accomplishments
1. Effects of genetics and management on grass water-soluble carbohydrates, and prediction of concentrations. Water-soluble carbohydrates (sugars and fructose polymers) of cool-season grasses can provide energy for grazing ruminants but may exacerbate the risk of equine pasture-associated laminitis, an extremely painful hoof condition triggered by diet and often coincident with gastrointestinal disorders. ARS scientists in Lexington, Kentucky, with University of Kentucky collaborators, used near-infrared reflectance spectroscopy and wet chemistry to build an equation predicting the amount of water-soluble carbohydrates in grasses with 90% accuracy. The equation was used to study effects of season and management on water-soluble carbohydrates of selected cool-season grasses. Afternoon increases in water-soluble carbohydrates, and higher levels in perennial ryegrass and tall fescue than in orchardgrass, were observed across a growing season. This is the first such study done in Kentucky. The equation will facilitate future analyses, and the information gained may help producers manage grazing in order to mitigate equine pasture-associated laminitis or optimize ruminant performance.
2. Measurement of water-soluble carbohydrates in red and white clovers. Clovers are often present in cool-season grass pastures, but relatively little is known about how much they contribute to the amount of water-soluble carbohydrates ingested by grazing animals. They may provide energy for ruminants but may exacerbate the risk of equine pasture-associated laminitis, an extremely painful hoof condition triggered by diet and often coincident with gastrointestinal disorders. ARS scientists in Lexington, Kentucky, with University of Kentucky collaborators, quantified water-soluble carbohydrates in repeatedly mowed red and white clovers at different times of day and year. Clovers were 8 to 10% water-soluble carbohydrate (freeze-dried matter basis). Preliminary starch analyses indicated that clovers were 2 to 6% starch (also a source of energy or a risk factor for equine pasture-associated laminitis), depending on time of day and year. This is the first such study done in Kentucky. The information may help producers to make pasture or grazing management decisions for horses or ruminants.
3. Phenolic compounds of cool-season grasses. Plant phenolic compounds are natural products that are sometimes antimicrobial. Some selectively inhibit gut bacteria contributing to gastrointestinal problems of grazing animals, thus even improving the efficiency of digestion by beneficial gut microorganisms. ARS scientists in Lexington, Kentucky, with University of Kentucky collaborators, studied the total phenolic content and phenolic profiles of five cool-season grasses to determine potential benefits to grazing horses or ruminants. The grasses differed in amounts and types of phenolic compounds present. Two phenolic compounds with known antimicrobial activity were present in the grasses studied. The results of this study are informing current research on cool-season grass phenolic compounds that inhibit ruminal ammonia-producing bacteria, thereby improving the efficiency of ruminant digestion.
4. Gene expression analysis of tall fescue harboring different endophyte strains show variable response to water stress. Tall fescue is one of the most abundant cultivated pasture grasses in the United States, with exceptional stress tolerances partly attributed to effects of its symbiotic fungal endophyte, Epichloë coenophiala. Unfortunately, ergot alkaloids produced by common toxic E. coenophiala (CTE) strains have negative effects on livestock. In contrast, novel non-toxic E. coenophiala (NTE) strains lack ergot alkaloids, but may provide insect deterrence or other fitness benefits to tall fescue. ARS scientists in Lexington, Kentucky, along with university collaborators in Kentucky, Oklahoma and Texas, analyzed gene expression profiles of tall fescue clones harboring the CTE and two NTE strains in response to water stress. The results suggested subtle and variable effects of the different endophyte strains on tall fescue gene expression. Also, where the endophyte confers protection, its effects on plant gene expression may help prime the plant for resistance, thereby allowing for better survival in future stress events. This information should aid breeding programs during selection of plant genotypes and endophyte strains for new variety releases.
Review Publications
Kramer, K.J., Kagan, I., Lawrence, L.M., Goff, B.M., Smith, S. 2020. Water-soluble carbohydrates of cool-season grasses: prediction of concentrations by near-infrared reflectance spectroscopy and evaluation of effects of genetics, management and environment. Journal of Equine Veterinary Science. 90:103014. https://doi.org/10.1016/j.jevs.2020.103014.
Kagan, I., Goodman, J.P., Seman, D.H., Lawrence, L.M., Smith, S. 2019. Effects of harvest date, sampling time, and cultivar on total phenolic concentrations, water-soluble carbohydrate concentrations, and phenolic profiles of selected cool-season grasses in central Kentucky. Journal of Equine Veterinary Science. 76:86-93. https://doi.org/10.1016/j.jevs.2019.05.005.
Kagan, I., Anderson, M.L., Kramer, K., Seman, D.H., Lawrence, L.M., Smith, S. 2019. Seasonal and diurnal variation in water-soluble carbohydrate concentrations of repeatedly defoliated red and white clovers in central Kentucky. Journal of Equine Veterinary Science. 84:102858. https://doi.org/10.1016/j.jevs.2019.102858.
Slaughter, L.C., Nelson, J.A., Carlisle, E., Bourguignon, M., Dinkins, R.D., Phillips, T.D., McCulley, R.L. 2019. Tall fescue and E. coenophiala genetics influence root-associated soil fungi in a temperate grassland. Frontiers in Microbiology. 10:2380. https://www.frontiersin.org/articles/10.3389/fmicb.2019.02380/full.
Azzouz-Olden, F., Hunt, A.G., Dinkins, R.D. 2020. Transcriptome analysis of drought-tolerant sorghum genotype SC56 in response to water stress reveals an oxidative stress defense strategy. Journal of Molecular Biology. 47:3291-3303. https://doi.org/10.1007/s11033-020-05396-5.
Dinkins, R.D., Nagabhyru, P., Young, C., West, C., Schardl, C.L. 2019. Transcriptome analysis and differential expression in tall fescue harboring different endophyte strains in response to water deficit. The Plant Genome. 12(2):180071.