Progress 10/01/15 to 09/30/19
Outputs
Target Audience:During the current reporting period, the target audience was a technical staff member, a graduate student, and two undergraduate students, at the University of Nebraska-Lincoln. (UNL). These individuals gained science-based knowledge through their involvement in educational programs (partly in conjunction with the Statistics Department at UNL), laboratory instruction and experiential learning opportunities. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?As outlined with regards to the second goal of this project, one staff member (Alec Kollman), one doctoral student (Napoleón Vargas Jurado), and two undergraduate students (Esdras Tuyishimire; Sarah Dannehl) benefitted from professional development and mentoring opportunities through their involvement in the W2012 project. This included engagement in developing and implementing laboratory procedures, statistical analysis of the data accumulated, and publication of those results as part of a dissertation and referred journal. How have the results been disseminated to communities of interest?Results from this project were disseminated to the scientific community through two peer-reviewed publications, a theater presentation at the Midwest Section meeting of the American Society of Animal Science, and a doctoral defense seminar on the University of Nebraska-Lincoln campus. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Two key components of an efficient cow herd are a minimum maintenance requirement and an ability to convert available energy from forage into calf weaning weight. Approximately 65% of total beef production costs are due to feed, with 70% of the total energy consumed by the cow-calf sector and 75% of a cow's total annual energy requirement due to maintenance. Identifying differences in metabolic efficiencies among individual cows, however, is difficult since forage intakes are rarely measured in grazing systems. Saturated hydrocarbons (n-alkanes) and long-chain alcohols (LCOH) can and have been used to estimate diet composition and feed intake in extensive pastoral systems. The utility of using such plant-waxes as dietary markers, however, depends on their precise and accurate measurement in forage and fecal samples. Laboratory protocols, including uniform methods for training personnel, were developed, tested and used at the University of Nebraska-Lincoln (UNL) to ensure reliable and repeatable assessment of these compounds. Doing so has resulted in the establishment of a nationally recognized lab. Furthermore, the reliability of the plant-wax marker methodology was successfully demonstrated in both a controlled (housed) and grazing study, along with establishment of novel statistical tools to improve estimation of diet composition. Combined, these accomplishments allow the reliable evaluation of diet selection and intake in grazing environments, with tremendous opportunity to improve the economic efficiency of cattle production systems. Goal (1): assess variation across space and time for n-alkane composition in unique classes of forages common to the Western United States, are noteworthy. Diet compositions and intakes of 30 crossbred heifers were estimated using n-alkanes in a sequence of 3 (year one) or 4 (year two) grazing studies. Smooth bromegrass was the dominant forage in the pastures, although other grasses were present (e.g., cheatgrass, Kentucky bluegrass, sedge). Individual heifers expressed some selectivity. Still, their estimated diet composition aligned with the botanical composition of the pastures (82 to 95% smooth broomegrass). Forage intake estimates were consistent across the grazing season (on average 2% body weight on a dry matter basis). Despite the lack of fine demarcations among heifers, sensible intakes were obtained in a grazing setting using n-alkanes. This research involved collaboration with Dr. Harvey Freetly (U.S. Meat Animal Research Center, Nebraska). Estimates of diet composition based on plant-wax markers have traditionally been obtained using nonnegative least-squares (NNLS) procedures. Alternative statistical approaches, built on a Bayesian framework, may more realistically account for variation among animals and other external factors that impact estimation of dietary choice. Using both field and simulated plant-wax marker data, the utility of six statistical approaches, including NNLS, were compared. By accounting for the repeated measurement of animals' dietary choices, and the genetic relationships among them, the accuracy of the estimates were higher than with NNLS. Dietary choices of 22 Angus-cross heifers were evaluated at both post-weaning and yearling age in a housed study. At each age, they were offered red clover and fescue hay as cubes. Diet composition was estimated using two statistical methods. Post-weaning, dietary choices were reliably estimated, with low residual error, regardless of the statistical approach adopted. The regression of observed on estimated red clover proportion range from 0.85 ± 0.08 to 1.01 ± 0.09 depending on the fecal sampling strategy used (a.m. or p.m. samples separately or combined). At yearling age, however, the estimates were less reliable. There was a tendency to overestimate the red clover proportion in diets of heifers preferring fescue, and vice versa. This was due to greater variability in n-alkane fecal concentrations in the yearling heifers. Still, overall the n-alkane technique provided a reliable tool for estimating diet choice in animals fed a simple forage diet. Goal (2): Provide professional development and mentoring opportunities for committee participants, young scientists, stakeholders, and graduate students. I continued to serve as the Chair of the graduate committee of Napoleón Vargas Jurado, a Ph.D. student at the University of Nebraska-Lincoln. On Nov. 16, 2019, Napoleón very successfully defended his dissertation Linear unmixing models: extensions and applications to the estimation of dietary (botanical) mixing proportions. He also published a manuscript Choices between red clover and fescue in the diet can be reliably estimated in heifers post-weaning using n-alkanes in the journal Animal. Two undergraduate students, Sarah Dannehl and Esdras Tuyishimire, continued their engagement in or research program. Sarah is from Nebraska and is pursuing a B.S. degree in Animal Science. She has recently applied to Veterinary Medicine programs as her ambition on graduation. Esdras is a student from Rwanda participating in the College of Agriculture and Natural Resources Undergraduate Scholarship Program. He is pursuing a B.S. degree in Integrated Science that is focused on conservation agriculture, entrepreneurship, leadership, and innovative thinking. Those disciplinary areas align with educational priorities of the Rwandan Ministry of Agriculture and Animal Resources.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2019
Citation:
Artegoitia, V. M., A. P. Foote, R. M. Lewis, and H. C. Freetly. 2019. Metabolomics profile and targeted lipidomics in multiple tissues associated with feed efficiency in beef steers. ACS Omega 4:3973-3982. doi.org/10.1021/acsomega.8b02494
- Type:
Journal Articles
Status:
Published
Year Published:
2019
Citation:
Vargas Jurado, N., A. E. Tanner, S. Blevins, J. Rich, D. Fiske, W. S. Swecker, Jr., H. M. McNair, and R. M. Lewis. 2019. Diet choice can be reliably estimated using n-alkanes at two stages of growth in beef cattle in controlled (indoor) studies. Animal 13:1907-1916. doi.org/10.1017/S175173111900017X
- Type:
Theses/Dissertations
Status:
Published
Year Published:
2019
Citation:
Vargas Jurado, N. 2019. Linear unmixing models: extensions and applications to the estimation of dietary (botanical) mixing proportions. Ph.D. Diss. University of Nebraska-Lincoln.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2019
Citation:
Vargas Jurado, N., R. M. Lewis, and K. M. Eskridge. 2019. Modeling repeated measurements of diet composition. J. Anim. Sci. 97(Suppl. 2):133 (Abstr.) doi.org/10.1093/jas/skz122.236
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Progress 10/01/17 to 09/30/18
Outputs
Target Audience:During the current reporting period, the primary target audience was a technical staff member, a graduate student, and two undergraduate students, at the University of Nebraska-Lincoln. (UNL). These individuals gained science-based knowledge through their involvement in educational programs (partly in conjunction with the Statistics Department at UNL), laboratory instruction, experiential learning opportunities and conference participation. The undergraduate students' involvement formed the core of for-credit internships, experiences that they formalized through a theater and a poster presentation at two undergraduate conferences held on the UNL campus. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?As specific to goal (2) of this project, a staff member, one doctoral student, and two undergraduate students benefited from participation in training activities and in professional development during the reporting period. One area of focus for professional development was our establishing a comprehensive training program in the lab procedures associated with analyzing plant-wax contents of samples. Such training is essential to ensure the reliable use of this methodology. Two undergraduate students - Sarah Dannehl and Esdras Tuyishimire - participated in the training. Concentrations of n-alkanes were quantified in pure and seven mixtures of corn silage and ground alfalfa hay. Error between extractions and Gas Chromatography injections were measured to gauge the consistency of their lab technique. Herbage compositions were estimated with non-negative least squares and assessed by regression of actual on estimated proportions. Slopes did not differ from one (P > 0.29), with good overall model fit (R2 = 0.98), validating the success of our training program with these students acquiring strong lab techniques. Following this training, these two students fine-tuned their skills by assisting in the n-alkane extractions of forage and fecal samples for both commercial and in-house research. Part of their work in the lab also has involved laboratory meetings in which we read and critiqued scientific literature related to our research. This allowed these students to gain a better understanding of the use of the plant-wax methodologies in a broader, applicable context. How have the results been disseminated to communities of interest?Results from this project were disseminated to the scientific community through two peer-reviewed publications, a poster presentation at a regional meeting, and a theater and poster presentation on the University of Nebraska-Lincoln campus. The annual meeting of the W2012 Multistate Hatch Project was hosted by the University of Idaho at the Nancy M. Cummings Research, Extension & Education Center, in Carmen, ID. Our team's contributions to project goals were shared during that project meeting. What do you plan to do during the next reporting period to accomplish the goals?Our key achievements this reporting period were (i) establishing robust lab protocols for evaluating both n-alkane and long-chain alcohol contents of forages and fecal samples; and (ii) training undergraduate students in carrying out those procedures. Building on those successes, our priority over the next reporting period will be to complete lab analyses of samples collected in collaborative research between the University of Nebraska-Lincoln and the U.S. Meat Animal Research Center. We will then prepare and submit further peer-reviewed journal publications based on that joint effort, further disseminating our results through participation in regional and/or national conferences. In addition, we will continue to work with colleagues at the Universities of Idaho and Vermont, and at North Dakota State University, on cooperative projects built on our expertise with the plant-wax marker technique.
Impacts
What was accomplished under these goals?
Feeding the cow herd is costly. However, within grazing systems, identifying differences in efficiencies is difficult since forage intakes are rarely measured. Saturated hydrocarbons (n-alkanes) and long-chain alcohols (LCOH) can and are being used to estimate diet composition and feed intake in extensive pastoral systems. However, the utility of using n-alkanes and LCOH as dietary markers depends on their precise and accurate measurement in forage and fecal samples. Laboratory protocols, including uniform methods for training personnel, were developed and tested at the University of Nebraska-Lincoln (UNL) to ensure reliable and repeatable assessment of these compounds. Doing so has resulted in the establishment of a nationally recognized lab used by research groups in four U.S. states to implement this technology in practice. The n-alkane profiles of individual forages found commonly in the Western U.S. vary with the geographic location, year, and phenology from which they were sampled. We therefore wanted to test the utility of the plant-wax marker approach to delineate plants typical of western rangelands. Three cool- and three warm-season grasses, and two legumes, were harvested at two stages of growth in two years in west central Nebraska. Encouragingly, the n-alkane and long-chain alcohol (LCOH) profiles of several of these forages were unique. The legumes could be clearly distinguished from the grasses. In most case, the high C32OH contents of the warm-season grasses helped to delineate them from the cool-season grasses. However, there were exceptions. Western wheatgrass, a cool-season grass, clustered with some of the warm-season grasses. Refinements in the plant-wax methodology remain. However, including LCOH among the markers used to distinguish forages in complex western rangelands will improve the reliability of estimates of dietary choices of cattle grazing such environments. Goal (1): assess variation across space and time for n-alkane composition in unique classes of forages common to the Western United States, are noteworthy. Measuring diet choice in grazing animals is challenging, complicating the assessment of feed efficiency in pasture-based systems. Plant-wax markers, such as n-alkanes, are proposed to provide reliable estimates of dietary choices and intakes. Still, their use in beef cattle has been relatively limited. The reliability of the n-alkane technique to estimate diet choices was tested in twenty-two Angus-cross heifers at both post-weaning and yearling age. At each age, they were offered free-choice red clover and fescue hay as cubes. Similarity between observed and estimated red clover proportions in the diet, as measured by a similarity index, was moderately high (P ≥ 0.42) regardless of physiological stage. At yearling age, estimated values tended to under-predict observed values as the proportion of red clover in the diet increased (P < 0.001). Still, in general, estimates were reliable suggesting n-alkanes provide a useful tool for evaluating dietary choices in cattle offered a small number of forages. The addition of long chain alcohols (LCOH) to n-alkanes may assist in the delineation of unique forages based on their plant-wax profiles. Laboratory measurements of n-alkanes have been shown to be consistently reliable; however, more work was needed to improve extraction of LCOH, and their quantification with Gas Chromatography (GC). Experiments were conducted in collaboration with the University of Nebraska-Lincoln Chemistry Instrumentation Center (UCIC) with GC-Mass Spectrometry (GC-MS; chemical ionization) in order to improve extraction techniques, and GC-Flame Ionization Detection (GC-FID) methodology, for LCOH. The main goals of the GC-MS experiment were to identify the presence or absence of C32OH in forage samples - currently there is no commercial standard for this compound - and to investigate the possibility of co-elution of other compounds at similar retention times to C30OH. Through the GC-MS, we were able to clearly delineate the presence of C32OH in samples, and thereby define a retention time for this compound to use in GC-FID analyses. The higher sensitivity, response and mass spectral information from the GC-MS identified co-eluting peaks with C30OH. From this, we established protocols for the GC-FID to clearly delineate the co-eluting compounds, allowing concentrations of C30OH to be more reliably assessed. This work was in collaboration Dr. Martha Morton and Dr. Thomas Smith in the Chemistry Department at the University of Nebraska-Lincoln. Collaborations continued with Dr. James Sprinkle (University of Idaho) and Dr. Michael Undi (North Dakota State University) to provide laboratory support to evaluate the n-alkane concentrations of forages and feces collected during forage intake studies based on pulse dosing protocols. Approximately 1,650 samples were extracted and assessed for n-alkane concentrations. A new collaboration was established with Dr. Sabrina Greenwood (University of Vermont), who is interested in using plant-waxes to estimate diet selection and feed intakes in dairy cattle managed in organic systems. Rather than dosing cattle with a synthetic n-alkane as the external marker (e.g., C32, C36) to determine intakes, carnauba wax, which contains high concentrations of the long-chain alcohol C32OH, will be used. Goal (2): Provide professional development and mentoring opportunities for committee participants, young scientists, stakeholders, and graduate students. Alec Kollman augmented his skills as lead research technician and manager of our lab focused on evaluating the plant-wax compositions of plant and animal (fecal) samples. A key development was his establishing dependable protocols to assess the long chain alcohol contents of forage and fecal samples. That effort was a close collaboration with the Chemistry Department at the University of Nebraska-Lincoln, with Alex developing new skills in Gas Chromatography-Mass Spectrometry. He also presented an update about our research at the annual multi-state project meeting associated with the project (W2012), which was held in Idaho. As program lead, I served as the Chair of the Graduate Committee of Napoleón Vargas Jurado, the inaugural student in a dual Ph.D. major in Animal Science and Statistics at the University of Nebraska-Lincoln. Napoleón published the paper Using a Bayesian hierarchical linear mixing model to estimate botanical mixtures in the Journal of Agricultural, Biological, and Environmental Statistics, and submitted another paper Diet choice can be reliably estimated using n-alkanes at two stages of growth in beef cattle in controlled (indoor) studies to the journal Animal. Two new undergraduate students joined our research group: Esdras Tuyishimire and Sarah Dannehl. Esdras is a student from Rwanda participating in the College of Agriculture and Natural Resources Undergraduate Scholarship Program (CUSP). He is pursuing a Bachelor of Science degree in Integrated Science that is focused on conservation agriculture, entrepreneurship, leadership, and innovative thinking, which align with the areas of need as identified by the Rwandan Ministry of Agriculture and Animal Resources. Sarah is a student from Nebraska pursuing a Bachelor of Science degree in Animal Science. Sarah has aspirations of attending veterinary school post-graduation.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2018
Citation:
Vargas Jurado, N., K. M. Eskridge, S. D. Kachman, and R. M. Lewis. 2018. Using a Bayesian hierarchical linear mixing model to estimate botanical mixtures. J. Agric. Biol. Environ. Statistics 23:190-207. doi.org/10.1007/s13253-018-0318-9
- Type:
Journal Articles
Status:
Accepted
Year Published:
2019
Citation:
Vargas Jurado N., A. E. Tanner, S. Blevins, J. Rich, D. Fiske, W. S. Swecker, Jr., H. M. McNair, R. W. Mayes, and R. M. Lewis. 2018. Diet choice can be reliably estimated using n-alkanes at two stages of growth in beef cattle in controlled (indoor) studies. Animal (Accepted with revisions).
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2018
Citation:
Lewis, R. M., H. C. Hamilton, E. J. Hilburger, A. M. Kollman, E. Tuyishimire, S. R. Dannehl, and H. C. Freetly. 2018. Can plant waxes be reliably used to estimate forage intakes in cattle? First Annual Agricultural Research Division Hatch Multistate Project Director Meeting, West Central Research and Extension Center, North Platte, NE
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Progress 10/01/16 to 09/30/17
Outputs
Target Audience:During the current reporting period, the primary target audience was beef cattle producers in Nebraska. Through two articles in the 2017 Nebraska Beef Cattle Report, opportunities for using plant-waxes to characterize dietary choices and feed intake in cattle grazing corn residue and mixed pastures were articulated. Such information can contribute to producers' management of such grazing systems. In addition, additional target audiences were a new staff member (research technician), two graduate students and two undergraduate student at the University of Nebraska-Lincoln (UNL). These individuals gained science-based knowledge through their involvement in educational programs (partly in conjunction with the Statistics Department at UNL), laboratory instruction, experiential learning opportunities and conference participation. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?As specific to goal (2) of this project, a staff member, two graduate students, and two undergraduate students benefited from participation in training activities and in professional development during the reporting period Training activities. As part of newly established dual Ph.D. program Animal Science and Statistics at the University of Nebraska-Lincoln, Napoleón Vargas Jurado, a Ph.D. student, gained expertise in advanced statistical methods (e.g., Bayesian hierarchical linear mixing model), which he has applied in the analysis and publication of project data. Additionally, a new staff member (Alec Kollman), a M.S. student (Emily Hilburger), and two undergraduate students (Ashley Buescher; Riley Hahn) gained expertise in the laboratory methods needed to evaluate the samples collected in field studies (forages; feces). Professional development. Emily Hilburger, an M.S. student, participated in a national conference (2017 ASAS-CSAS Annual Meeting and Trade Show), giving an oral presentation. Alec Kollman, a recently hired research technician, participated in the 2017 W2012 Multistate Hatch Project meeting, presenting project results. How have the results been disseminated to communities of interest?Results from this project were disseminated to the scientific community through a peer-reviewed publication, two extension articles and a presentation at national meeting. The annual meeting of the W2012 Multistate Hatch Project was held Eastern Oregon Agricultural Research Center, Burns, Oregon. Our team's contributions to project goals were shared during the project meeting. What do you plan to do during the next reporting period to accomplish the goals?Since the start of the project, there has been considerable focus on designing and conducting experiments, with the accumulation of a large of number of forage and fecal samples. As evidence from project outcomes, good progress with the analysis of those samples, and reporting our results, has been achieved. However, with a new research technician being hired, their initial emphasis was on completing an extensive and comprehensive training program. Furthermore, one graduate student, and both undergraduate students, who were part of the team graduated. Lab work therefore was unavoidably delayed. With expertise now re-established, our main focus over the next report period will be to re-double our efforts to complete planned analyses. To further accelerate that effort, new students also will be recruited to participate in this program. The outcomes of these activities will be preparation and submission of further publications, participation in conferences, and the dissemination of the key results to stakeholders.
Impacts
What was accomplished under these goals?
Feeding the cow herd is costly. However, within grazing systems, identifying differences in efficiencies is difficult since forage intakes are rarely measured. Saturated hydrocarbons (n-alkanes) are being used to estimate diet composition and intake. However, the utility of using n-alkanes as dietary markers depends on their precise and accurate measurement in forage and fecal samples. Such reliability only comes with use of standardized protocols and methodical training. To ensure the dependable use of this tool, a lab certification program should be established based on a common training program and analytical procedures. Using an agreed rubric, technicians should demonstrate a prescribed level of skill with the technique as part of the lab certification process. Routine re-testing of technicians also should be implemented for a lab to remain certified. The n-alkane profiles of individual forages found commonly in the Western U.S. vary with the geographic location, year, and phenology from which they were sampled. Furthermore, classes of grasses (i.e., cool season, warm season) could not be discriminated based on their n-alkane profiles. Given the complexity of the botanical makeup of Western rangelands, the use of n-alkanes alone as dietary markers is inadequate to estimate diet composition and intake of grazing ruminants. Given the importance of enhancing feed utilization in grazing environments, the investigation of a broader set of plant-wax markers (e.g., long chain alcohols; fatty acids) is needed if this methodology is to be considered as a potential tool to estimate diet composition in extensive systems. Goal (1): assess variation across space and time for n-alkane composition in unique classes of forages common to the Western United States, are noteworthy. Laboratory protocols were developed and implemented at the University of Nebraska-Lincoln to ensure reliable and repeatable assessment of plant wax concentrations of forage and fecal samples using gas chromatography. This involved designing test samples with known contents of plant waxes, and establishing a training program to allow staff and students to develop the requisite laboratory skills to consistently measure these compounds. These measurements are central to using plant waxes to estimate diet composition and feed intake in grazing ruminants. Key methodological and statistical procedures for using n-alkanes to estimate diet composition and feed intake were tested experimental in controlled (indoor) and simple pasture settings. Although there were inaccuracies, intakes were sufficiently well estimated to reliably rank animals. Since genetic selection can loosely be thought of as choosing animals based on ranks, plant-waxes may contribute to breeding programs designed to improve efficiency. Three cool- and 3 warm-season grasses, and 2 legumes, typical of western rangelands were harvested at 2 stages of growth in 2 years and 2 locations. The n-alkane profiles of several of these forages were unique. However, in a mixed diet, the contributions of the individual plants could not be well estimated. Refinements in the methodology are needed if plant waxes are to be used as reliable dietary markers for cattle grazing complex western rangelands. Goal (2): Provide professional development and mentoring opportunities for committee participants, young scientists, stakeholders, and graduate students. A considerable number of opportunities for professional development occurred during the reporting year. Napo Vargas, a doctoral student, submitted a journal paper titled "Using a Bayesian hierarchical linear mixing model to estimate botanical mixtures" to the Journal of Agricultural, Biological, and Environmental Statistics, which has been accepted with revisions. Emily Hilburger, a master's student, completed her thesis (August 2017) entitled "Assessing plant-wax markers as a tool to estimate intake and diet composition in beef cattle," and presented her research at the 2017 ASAS-CSAS Annual Meeting and Trade Show (July 8-12, 2017, Baltimore, Maryland). Alec Kollman was hired as research technician to develop and manage a state of the art laboratory to evaluate the plant-wax compositions of plant and animal (fecal) samples. A key outcome of his current year's activities was his gaining the expertise to develop procedures for quality assurance and laboratory standardization. He also presented an update about the research at the annual multi-state project meeting associated with the project (W2012), which was held in Oregon. Lastly, two undergraduate students - Ashley Buescher and Riley Hahn - further developed and refined their laboratory skills to analyze the plant wax concentrations of samples collected in a variety of studies.
Publications
- Type:
Journal Articles
Status:
Accepted
Year Published:
2017
Citation:
Vargas Jurado, N., K. M. Eskridge, S. D. Kachman, and R. M. Lewis. 2017. Using a Bayesian hierarchical linear mixing model to estimate botanical mixtures. J. Agric. Biol. Environ. Statistics
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2017
Citation:
Hilburger, E. J., H. C. Wilson, H. C. Freetly, and R. M. Lewis. 2017. Analysis strategies for calculating intake for cattle with plant waxes. J. Anim. Sci. 95(E-Suppl. 4):310 (Abstr.). doi:10.2527/asasann.2017.634.
- Type:
Other
Status:
Published
Year Published:
2017
Citation:
Hamilton, H.H., J.D. Volesky, and R.M. Lewis. 2017. Evaluation of plant-waxes to estimate forage intake in grazing cattle In: 2017 Nebraska Beef Cattle Report, University of Nebraska Extension, MP 104, p. 69-72.
- Type:
Other
Status:
Published
Year Published:
2017
Citation:
Vargas Jurado, N., H.H. Hamilton, and R.M. Lewis. 2017. Delineating complex forage mixtures using plant-wax markers. In: 2017 Nebraska Beef Cattle Report, University of Nebraska Extension, MP 104, p. 73-75.
- Type:
Theses/Dissertations
Status:
Published
Year Published:
2017
Citation:
Hilburger, E. J. 2017. Assessing plant-wax markers as a tool to estimate intake and diet composition in beef cattle.
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Progress 10/01/15 to 09/30/16
Outputs
Target Audience:During the current reporting period, the target audience was three graduate students and one undergraduate student at the University of Nebraska-Lincoln (UNL). These students gained science-based knowledge through their involvement in educational programs (partly in conjunction with the Statistics Department at UNL), laboratory instruction, experiential learning opportunities and conference participation. As illustrations of outcomes, a doctoral student developed computational tools to more reliably predict dietary choices in free-grazing herbivores using plant wax markers. He presented those results at two national conferences over summer. Furthermore, the full team of students collaborated in research at the U.S. Meat Animal Research Center, gaining hands-on experience in the design and conduct of studies to predict dietary choices and intakes in cattle in controlled (pen) and in grazing conditions. They were also trained in the requisite laboratory skills (e.g., gas chromatography) to analyze the samples collected in those studies. Such laboratory training formed a for-credit summer internship completed by the undergraduate student. The team also participated in the 5th Grazing Livestock Nutrition Conference in July presenting an invited poster. Furthermore, two of the graduate students attended and presented updates about their research at the annual multi-state project meeting associated with the project (W2012), which was hosted by UNL in Scottsbluff, NE, in August. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?As specific to goal (2) of this project, three graduate students and one undergraduate student benefitted from participation in training activities and in professional development. Training activities. As a collaboration between the Animal Science and Statistics Departments at the University of Nebraska-Lincoln, Napoleón Vargas Jurado, a PhD student, gained expertise in advanced statistical methods (Bayesian statistics), which he then applied in the analysis and publication of project data. Additionally, both a graduate (Emily Hilburger) and undergraduate (Ashley Buescher) gained skills in the scientific process by participating in the design and implementation of field studies conducted in collaboration with U.S. Meat Animal Research Center (Clay Center, NE). Through extensive training, they also gain expertise in the laboratory methods needed to evaluate the samples collected in the field studies (forages; feces). For the undergraduate student, these activities served as a for-credit summer internship. Professional development. Mr. Vargas Jurado participated in two national conferences, presenting both an oral presentation and poster. Three graduate students (Hannah Hamilton, Ms. Hilburger, Mr. Vargas Jurado) and one undergraduate student (Ms. Buescher) attended the 5th Grassland Livestock Nutrition Conference. They assisted in preparing and presenting an invited poster. Ms. Hamilton and Ms. Hilburger also participated in the 2016 W2012 Multistate Hatch Project meeting, presenting results from their research. How have the results been disseminated to communities of interest?Results from this project were disseminated to the scientific community through peer-reviewed publications and presentations at national meetings. The annual meeting of the W2012 Multistate Hatch Project was hosted by the University of Nebraska-Lincoln in Scottsbluff, NE. Beyond the project meeting itself, this activity included the interaction of the project team with stakeholders in the Sandhills region of NE through ranch visits and an evening session entitled "how to bring young producers into the ranching and livestock business". That discourse allowed for a useful sharing of project information. What do you plan to do during the next reporting period to accomplish the goals?There are two main activities planned for the next reporting period. Activity one. Since the inception of the project, there has been considerable focus on designing and conducting experiments. This has resulted in the accumulation of a large of number of samples requiring laboratory analysis. Therefore a main focus of the next reporting period will be to progress with those analyses, which will culminate in the completion of a student's MS thesis project. Activity two. As the complexity of a plant community increases, delineating the composition of animal diets inherently becomes more difficult. Thus far, ten dietary markers have been used to discriminate eight plant species. Despite the unique marker profiles of several of these species, the contributions of the individual plants to a mixed diet could not be estimated. As noted earlier, refinements in the methodology are needed if plant waxes are to be used as reliable dietary markers for cattle grazing western rangelands. Therefore, in the upcoming year, a paradigm-shift in the statistical methodologies used to estimate diet composition will be explored. The traditional estimation methodology (non-negative least squares) ignores relationships among the plant-wax markers, introducing biases. A probabilistic (Bayesian) approach that accounts for such relationships may improve matters. In a preliminary study, such appeared to be the case. Therefore, alternative methods to estimate the botanical composition of diets using plant-wax markers will be investigated further. Outcomes of these activities will include preparation and submission of journal publications, participation in national conferences, and the dissemination of the key results to stakeholders.
Impacts
What was accomplished under these goals?
The maintenance of the herd is estimated to contribute 70% of the costs to cow-calf operations, and improving feed efficiency is therefore a priority. However, within pasture systems, obtaining quantitative information on intakes and dietary choices of individual cows is challenging. One approach involves plant-wax markers such as n-alkanes. These markers can be used to predict intakes and dietary choices when the wax profiles among plant species are sufficiently distinct. The aim of this project is to determine the value of plant-wax markers in assessing important components of cow efficiency in pasture systems characteristic of Nebraska specifically, and in western states more generally. The reliable use of plant-wax markers to predict feed efficiency in grazing cattle depends on establishing robust laboratory procedures for evaluating their contents in forages. Such has been achieved. Three technicians in two labs measured the plant-waxes in pure and nine mixtures of two common forages. With training, the individual technicians could reliably estimate the composition of these plant mixture using these markers. Establishing such a program for quality assurance and laboratory standardization clearly predicates the consistent use of plant waxes as dietary markers. Defining dietary choices among cattle in commercial pasture systems using plant-waxes depends on the forages eaten being distinctive in their wax profiles. Three cool- and three warm-season grasses, and two legumes, typical of western rangelands were harvested at two stages of growth. The plant-wax marker profiles of several of these forages were unique. However, in a mixed diet, the contributions of the individual plants could not be estimated. Refinements in the methodology are therefore still needed if plant waxes are to be used as reliable dietary markers for cattle grazing western rangelands. Goal (1): assess variation across space and time for n-alkane composition in unique classes of forages common to the Western United States, are noteworthy. Three specific accomplishments toward this goal were achieved. Firstly, in a second year of collections, three cool- and three warm-season grasses, and two legumes, were sampled at their peak vegetative and mature states at the West Central Research and Extension Center, North Platte, NE. Collection sites were primarily native mixed-grass rangeland within the rolling plains typical to West Central NE. Beyond the standard forages collected by all participating stations, needle-and-thread, little bluestem and lead plant (legume) also were sampled. Secondly, the robustness of laboratory procedures to quantify the plant-wax contents of plants were tested. Three technicians in two labs measured the concentrations of four n-alkanes (C27, C29, C31 and C33) in pure and nine mixtures of tall fescue and red clover. Labs, and technicians within labs, differed in their quantification of the individual n-alkanes. However, within technician fescue contents of the mixtures were estimated reliably, although consistently high for two technicians. Thirdly, the delineating the composition of forage communities using plant waxes depends on the profiles of those markers being sufficiently distinct. The concentrations of five n-alkanes and six long chain alcohols (-OH) were determined in there cool- and three warm-season grasses, and in two legumes, harvested at two phenologies (vegetative; mature). Cattle diets were simulated and their species composition estimated. At both phenologies, legumes were distinct from grasses, reflecting higher C29, C26-OH and C30-OH concentrations. Blue grama was unique in its C33 and C32-OH contents. However, the eight plant species could not be clearly discriminated in these diets. These results contribute to two journal publications and presentations at three national conferences. Goal (2): Provide professional development and mentoring opportunities for committee participants, young scientists, stakeholders, and graduate students. A considerable number of opportunities for professional development occurred during the reporting year. Napoleón Vargas Jurado, a PhD student, participated in two national meetings: the Conference on Applied Statistics in Agriculture (May 1-3, 2016; Manhattan, KS) and the ASAS-ADSA-CSAS-WSASAS Joint Annual Meeting (July 19-23, 2016; Salt Lake City, UT). His presentations focused on his development of computational methods (a Bayesian hierarchical model) to more reliably predict dietary choices and feed intakes in grazing herbivores using plant-wax markers. This work was a collaboration between the Animal Science and Statistics Departments at the University of Nebraska-Lincoln. In a collaboration with the U.S. Meat Animal Research Center (Clay Center, NE), Emily Hilburger, an MS student, and Ashley Buescher, an undergraduate student, were involved in the second year of experiments testing the utility of using plant-wax markers to predict dietary choices and intakes in cattle in controlled (pen) and in grazing conditions. Beyond field work, this effort involved their developing the requisite laboratory skills (e.g., gas chromatography) to analyze the plant-wax contents of the plant and fecal samples collected. Ms. Buescher's involvement was as a summer internship in the Engler Agribusiness Enterprise Program at the University of Nebraska-Lincoln. Three graduate students (Hannah Hamilton, Ms. Hilburger, Mr. Vargas Jurado) and one undergraduate student (Ms. Buescher) attended the 5th Grassland Livestock Nutrition Conference (July 17-19, 2016; Park City, UT). Lastly, Ms. Hamilton and Ms. Hilburger participated in the 2016 W2012 Multistate Hatch Project meeting, which was hosted by the University of Nebraska-Lincoln (Aug. 7-10, 2016; Panhandle Research and Extension Center, Scottsbluff, NE). At the meeting, they presented results from their research.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2015
Citation:
Vargas Jurado, N., A. E. Tanner, S. R. Blevins, H. M. McNair, R. W. Mayes, and R. M. Lewis. 2015. Long-chain alcohols did not improve predictions of the composition of fescue and red clover mixtures over n-alkanes alone. Grass Forage Sci. 70:499-506.
- Type:
Journal Articles
Status:
Published
Year Published:
2015
Citation:
Vargas Jurado, N., A. E. Tanner, S. R. Blevins, J. Rich, R. W. Mayes, D. Fiske, W. S. Swecker, Jr., and R. M. Lewis. 2015. Feed intake and diet selection in Angus-cross heifers of two frame sizes at two stages of growth. J. Anim. Sci. 93:15651572.
- Type:
Journal Articles
Status:
Published
Year Published:
2016
Citation:
Lewis, R. M., N. Vargas Jurado, H. C. Hamilton, and J. D. Volesky. 2016. Are plant waxes reliable dietary markers for cattle grazing western rangelands? Proc. 5th Grazing Livestock Nutrition Conference. J. Anim. Sci. 94(S6):93-102.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2015
Citation:
Vargas Jurado, N., A. E. Tanner, and R. M. Lewis. 2015. Using Bayesian inference to delineate diet composition of mixed forages. J. Anim. Sci. 93(Suppl. s3):284 (Abstr.).
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2016
Citation:
Vargas Jurado, N., K. M. Eskridge, S. D. Kachman, and R. M. Lewis. 2016. Estimating botanical mixtures using plant-wax markers and a Bayesian hierarchical model. In: Conf. Appl. Statistics Agric., Manhattan, KS.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2016
Citation:
Vargas Jurado, N., K. M. Eskridge, and R. M. Lewis. 2016. A Bayesian approach to unmixed diet composition. J. Anim. Sci. 94(E-Suppl. 5):292 (Abstr.).
- Type:
Theses/Dissertations
Status:
Published
Year Published:
2016
Citation:
Hamilton, H. 2016. Validating laboratory techniques that influence estimates of intake and performance in beef cattle. MS Thesis, University of Nebraska, Lincoln.
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