Source: UNIVERSITY OF NEBRASKA submitted to
EVALUATING ALLOSTATIC LOAD INDEXES FOR FEEDLOT SHEEP AND CATTLE TO BETTER UNDERSTAND HEAT STRESS SUSCEPTIBILITY
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
TERMINATED
Funding Source
AFRI COMPETITIVE GRANT
Reporting Frequency
Annual
Accession No.
1031859
Grant No.
2024-67012-42026
Project No.
NEB-26273
Proposal No.
2023-09799
Multistate No.
(N/A)
Program Code
A1251
Project Start Date
Apr 1, 2024
Project End Date
Jun 12, 2024
Grant Year
2024
Project Director
Gibbs, R.
Recipient Organization
UNIVERSITY OF NEBRASKA
(N/A)
LINCOLN,NE 68583
Performing Department
(N/A)
Non Technical Summary
The emergence of climate change threatens the sustainability of animal agriculture and creates a critical need to identify livestock at the highest risk for heat stress susceptibility. However, no such advancements have been made, and producers cannot proactively manage these high-risk animals during critical times of production. Studies in zoo wildlife indicate that predictive indexes, often referred to as allostatic load indexes, determined from a panel of biomarkers can effectively predict poor outcomes of subsequent stress. The proposed project is designed to determine optimal allostatic load indexes for feedlot sheep and cattle to better understand individual differences in heat stress resiliency. It will test the hypothesis that these indexes will predict poor health and performance in animals experiencing heat stress. To test this hypothesis, this study will aim to correlate candidate index biomarkers with performance outcomes in finishing lambs prior to and throughout chronic heat stress and in finishing beef steers in a midwest feedlot prior to, during, and after sudden changes in environmental conditions. Successful completion of this project will provide a much-needed step toward strategies that improve on-farm decision-making during heat stress events to allocate available resources more appropriately.
Animal Health Component
100%
Research Effort Categories
Basic
50%
Applied
50%
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
3063310102050%
3153610102050%
Knowledge Area
306 - Environmental Stress in Animals; 315 - Animal Welfare/Well-Being and Protection;

Subject Of Investigation
3610 - Sheep, live animal; 3310 - Beef cattle, live animal;

Field Of Science
1020 - Physiology;
Goals / Objectives
Heat stress in finishing livestock continues to emerge as a significant and persistent barrier to sustainable food animal production. Thus, producers and feedlots are continually challenged to implement large-scale infrastructure changes and treatment strategies to reduce the impact of heat stress. While these management strategies can help mitigate the effects of heat stress, they can be costly to implement and maintain. Therefore, producers and feedlots would benefit from management strategies that identify high-risk individuals who are more susceptible to heat stress to allocate these costly resources more appropriately. With this in mind, this study's overall goal/objective is to evaluate the effectiveness of a predictive index (allostatic load index) in pre-determining individual differences in heat stress resiliency. Previous research has indicated that such indexes are effective in overcoming the natural variability of individual biomarkers often used to measure stress in livestock (e.g., cortisol) as a more comprehensive assessment of dynamic somatic system responses. To this end, our objectives are to: 1) determine allostatic load indexes that effectively identify finishing lambs at high risk for poor performance during chronic heat stress and 2) determine allostatic load indexes that effectively identify finishing steers with an increased susceptibility for heat stress when exposed to sudden changes in environmental conditions.
Project Methods
Objective 1.) Determining allostatic load indices that effectively identify finishing lambs at high risk for poor performance and health during chronic heat stress. This study will compare blood sample analysis and performance/health in 36 thermoneutral controls and 36 chronic heat-stressed wether lambs.1. Animals and Blood Samples: This study will utilize blood/plasma samples, health data, and performance data banked from 3 separate but similar studies from 2019 to 2023. For all studies, lambs were individually housed and randomly assigned to thermoneutral or heat stress (40°C, THI=86 for 12 h/d; 35°C, THI=82 for 12 h/d) conditions for 30 days. Control lambs were pair-fed to the average of the heat-stressed group. Whole blood analysis was performed, and plasma was isolated from blood samples collected via jugular venipuncture on d 0, 7, 14, and 21 of the treatment period. Banked data includes the following: Whole blood analysis, including blood glucose, lactate, blood gasses, pH, blood acid/base balance, total differential white blood cell counts, and hematology values. Data to be collected from banked plasma samples: blood metabolites related to glucose and lipid metabolism, stress biomarkers including epinephrine, cortisol, and ACTH, and immune factors including haptoglobin, heat shock protein 70, immunoglobin G, and circulating cytokine biomarkers.2. Animal Performance and Health Data: Growth metrics and health data were collected under basal conditions on d 0, throughout the treatment period, and at the end on d 30. Data collected includes bodyweight, rectal temperature, respiratory rates, intake, average daily gain, ultrasound and BIA-estimated body composition, heart rate, and blood pressure. Performance of each heat-stressed lamb will be determined by the difference in its value for these metrics from the average of thermoneutral controls.3. Allostatic Load Index Scoring: Initial allostatic load index scores will be calculated from banked whole blood analysis, planned plasma analysis, and banked performance and health data collected at d 0 of the treatment period. Each calculated version of allostatic load index will then be compared via correlation analyses to growth and health performance. Likewise, allostatic load index will be compared to stress biomarkers measured throughout the heat-stress period.Objective 2.) Determine allostatic load indexes that identify feedlot steers at high risk for heat stress susceptibility. This study will evaluate 24 feedlot steers finished at the West Central Research & Extension Center at feedlot entry, throughout the finishing period during heat events, and at harvest.1. Blood sampling and analysis: A total of 6 draws/steer will be collected at the following timepoints: I. at feedlot entry under thermoneutral conditions, II. on each day of the 1st 48-hour heat event (THI>83 for 2 consecutive days), III. on each day of the 2nd 48-hour heat event, and IV. just prior to harvest. Whole blood analysis and plasma analysis will be preformed for the same biomarkers described in objective 1.2. Animal Performance and Health Evaluation: Bodyweight, ultrasound, and BIA-estimated body composition, hair shed scores, panting scores, and rectal temperatures will be collected at each timepoint of the finishing period described above. Growth performance will also be evaluated during heat events for metrics including feed intake, water intake, and average daily gain. Carcass metrics, including hot carcass weight, rib-eye area, marbling score, and back fat, will be collected at harvest.3. Allostatic Load Index Scoring: Biomarkers and animal performance metrics for allostatic load indexes will be measured in samples collected at feedlot entry under thermoneutral conditions. These will be correlated with growth metrics at the end of the finishing period and health indicators measured throughout and at the end finishing.

Progress 04/01/24 to 06/12/24

Outputs
Target Audience:The target audience that we have reached and will continue to reach with this project includes individuals working in the fields of animal agriculture, stress physiology, and meat production. In the 1st year of this project, our efforts to reach this target audience have included presenting scientific talks and posters at the annual national meeting for the American Society of Animal Science and at multiple local and regional meetings. Data and information about this project were also presented to scientific audiences at the W4173 and NC1184 multistate meetings. Changes/Problems:Problems/Issues: We have not encountered any major issues. As a result, the project remains on schedule. Changes: I was recently offered and accepted a faculty position at North Dakota State University. Per the advice of the NIFA Program Officers, I am requesting that the funding award for this project be transferred to a standard grant. This request has the support of both UNL and NDSU, and I have been in communication with the Program Officers. Because of the nature of the project, the requested transition is not expected to have more than a minimal effect on our progress. Moreover, my fellowship advisor has committed in writing to his continued support of the project to its successful completion, as needed. What opportunities for training and professional development has the project provided?As a post-doctoral trainee, I have gained broad experiences in specific areas of live-animal research, including new experiences with beef cattle. Moreover, I have gained critical experiences in managing all aspects of a large-scale, team-driven research project. In addition to the specific components described above, this opportunity has allowed me to see firsthand how a properly-designed research project will build upon the previous project and lead into the next project of the research stream. I have also gained a better understanding of factors that should go into the decision-making associated with different areas of the project. Under the mentorship of experts, I have experienced to some degree each of the components for independent research described in my training plan in this early reporting period. How have the results been disseminated to communities of interest?The objectives of the project have been described in local and regional seminars and to stakeholders such as the Nebraska Sheep & Goat Producers Association via ongoing extension activities. This has helped in the vetting process for the project and has helped to reassure the value of our project goals. As indicated in the project narrative of the application, we expect the major products of the project (species-specific allostatic load indexes) to be ready for broad dissemination in later reporting periods. What do you plan to do during the next reporting period to accomplish the goals?In the next reporting period, we will request that the project be moved to a standard grant, but we do not anticipate this to have any major effects on the research accomplishments or timeline of the next reporting period. Our plan for the next period is to test the ability of our initial predictive indexes to accurately and reliably identify individual animals that were highly vulnerable to heat stress as indicated by their health status and growth performance. We will then be positioned to revise our indexes as needed and begin designing the next project to test the final indexes under broader stress conditions.

Impacts
What was accomplished under these goals? Research Accomplishments: Objective 1. Determine allostatic load indexes that effectively identify finishing lambs at high risk for poor performance during chronic heat stress. Blood samples and behavioral indicators have been collected from all control and heat-stressed animals needed for the completion of this study (72 total sheep). During this 1st reporting period, we assessed the first 20 biomarkers from our initial list of 26 parameters. We also developed critical syntax templates for assessing each biomarker and determining its inclusion/exclusion from the allostatic load index. From this early progress, examples of promising indicators include circulating HSP70 and lactate, to name a few. Conversely, circulating glucose and carbon dioxide are examples of biomarkers that show little promise as allostatic load indicators in sheep. Objective 2. Determine allostatic load indexes that identify feedlot steers at high risk for heat stress susceptibility. Like the 1st objective, all biological samples and performance data from the required 48 beef steers were collected in this initial reporting period. Moreover, we analyzed about one-third of our candidate biomarkers. Initial correlation analyses were performed, and initial predictive indexes were created using an approach similar to the one used for sheep in Objective 1. We have begun the process of assessing the fit of individual candidate biomarkers, which positions us to begin testing the quality of our predictive indexes in our heat-stressed livestock steers over the next reporting period. Training Accomplishments: As part of this fellowship project, I gained guided experience in numerous areas that will increase my success as an independent researcher. Specific areas include: a. Project management, including procurement of animals and other necessary resources, assuring compliance with university, state, and federal oversight, developing effective schedules and timelines, and fulfilling reporting and communication obligations. b. Budget management, including coordinating with USDA and UNL business office personnel to ascertain information, seeking cost effective options for resources and maintaining appropriate supply reserves, and keeping up-to-date records and reports. c. Training of personnel, including arranging the necessary manpower for each component of the project, teaching new personnel necessary techniques and approaches, and advising senior personnel on how to best ensure safety for all individuals and animals involved. d. Laboratory techniques, including identification, development, and validation of new assays for sheep and cattle bio samples. e. Approaches to statistical analysis, including broad correlation and regression models, predictive algorithms, and testing of statistical assumptions. f. Live-animal research techniques, including skeletal muscle and adipose biopsies, ultrasound estimates of muscle size, beef cattle husbandry and nutrition, breaking/training, and facilities upkeep. Summary: The findings from this early reporting period help to establish the fundamental basis for using allostatic load index to identify the most stress-susceptible individuals in a livestock herd or flock. They also provide critical initial information regarding the effectiveness/ineffectiveness of specific biomarkers as index components. Most importantly, they set the project up for initial testing of our first few predictive indexes under real heat-stress conditions in the next reporting period.

Publications