Performing Department
(N/A)
Non Technical Summary
Environmental heat stress during the summer months reduces the health and welfare, growth performance, and value of US livestock every year. Unfortunately, the difficulty, expense, and ineffectiveness of mitigating environmental conditions make it unrealistic in many cases. Therefore, US livestock producers would most benefit from bioactive dietary supplements and pharmaceutical strategies that minimize the impact of heat stress on their animals. Sustained heat stress and high body fat both cause systemic inflammation in livestock, and we hypothesize that treating this inflammation with anti-inflammatory dietary compounds will reduce the losses in health and growth that result from heat stress, particularly in high-fat finishing livestock. We will test this by exposing finishing lambs with mostest and high body fat to chronic heat stress. Our 1st objective is to determine the benefit of treating the inflammation in these animals on comprehensive indicators of health and well-being as well as growth and body composition. Our 2nd objective is to determine how these changes affect behaviorial changes that are predictive of poor welfare using a novel artificial intellegence monitoring system. We expect the results of this study to show that systemic inflammation is an effective target for intervention strategies in finishing livestock experiencing heat stress. Identifying such mechanistic targets for improving heat stress outcomes is a much-needed step for improving animal welfare, efficient food production, and agricultural sustainability.
Animal Health Component
100%
Research Effort Categories
Basic
50%
Applied
50%
Developmental
0%
Goals / Objectives
Heat stress in livestock is frequently unavoidable, making strategies to manage its impact on survival, health, and productivity essential. Such strategies require the identification of effective physiological targets to obtain the best possible welfare outcomes, as healthy animals are more productive. To this end, the overarching goal of the project is to determine if mitigating recently identified heat stress-induced systemic inflammation via dietary supplements improves physiological and behavioral indicators of animal welfare. Inflammatory factors mediate stress responses and modify organ function. Moreover, inflammatory activity can be controlled by bioactive compounds. Because inflammation is a component of heat stress and an outcome of adiposity, understanding how to mitigate it with practical approaches is a major step toward better welfare in finishing livestock facing inevitable heat events.In Objective 1, we will assess the impact of inflammatory mitigation on physiological indicators of welfare and health, including stress hormones and cytokines, hyperventilation, hyperthermia, weight loss, cardiovascular health, joint lameness, organ pathologies, and transcriptomic changes.In Objective 2, we will assess the predictive associations between behavioral changes and compromised welfare using machine-learning technology with the NUtrack Livestock Monitoring System.
Project Methods
Animals. Suffolk wether lambs (40 ± 2 kg) with moderate (≤ 3 mm) or high (5-8 mm) back fat thickness will be individually penned and fed a finishing ration. Lambs will be housed at 40°C (THI=86) for 30 days. Thermoneutral controls will be pair-fed. Lambs will also be supplemented dietary ω-3 PUFA (25 mg/kg/d) or soybean oil placebo daily from 14 days prior to heat stress through the end of the study.Objective 1. Determine the benefits of mitigating heightened inflammation on physiological indicators of welfare & tissue regulation in heat-stressed lambs with high adiposity.Cardiovascular assessments. Heart rate, cardiac rhythm, and blood pressure will be determined weekly with a multi-parameter veterinary monitor. Electrocardiograms will be recorded to determine average heart rate and heart rate variability and to detect any arrhythmias. Systolic, diastolic, and mean arterial blood pressures will be recorded under gentle restraint.Respiratory rate, core body temperature, & bodyweight. Respiration will be determined by the NUtrack system. Core body temperatures will be estimated from morning, mid-day, and evening rectal temperatures measured weekly by digital thermometer. Lamb weights and ultrasound-estimated bat fat thickness will be recorded weekly and compared to dietary intake to estimate metabolic efficiency.Stress & inflammation biomarkers. Weekly blood and salivary samples will be collected to assess biomarkers for health and stress. Differential blood cell counts will be performed with a veterinary hematology analyzer to assess circulating blood cell populations. Blood plasma concentrations of cortisol, TNFα, IL-6, haptoglobin, and epinephrine will be determined by ELISA. Cortisol and TNFα concentrations will also be determined in concurrently collected salivary samples. Protein will be extracted from snap-frozen samples of skeletal muscle, liver, duodenum, and kidney collected at harvest. Protein expression for the stress signaling components will be determined by western immunoblot.Health biomarkers. Weekly blood samples will be analyzed for health status indicators. Whole blood will be assessed with an ABL90 FLEX blood gas analyzer for gases and metabolites indicative of proper metabolic homeostasis, renal/hepatic function, and acid/base balance. Blood plasma will be assessed with a Vitros 250 chemistry analyzer for enzymes indicative of stress-induced damage to liver, muscle, and pancreatic tissues.Tissue pathologies. At necropsy, heart, lungs, GI tract, liver, kidneys, spleen, and adrenals will be collected and weighed. Samples of the heart, lungs, liver, kidneys, rumen, duodenum, pancreas, adrenals, and bladder will be assessed for pathologies by the Nebraska Veterinary Diagnostic Center. Thickness of the left ventricle, right ventricle, and septum of the heart will be determined using a digital caliper. Adrenal cortical & medullary hypertrophy will be assessed by immunostaining. Hooves and fetlock joints will be assessed for lesions consistent with lameness by VDC experts. Bone density will be determined by histology in cannon bone cross sections. Energy reserves will be estimated from muscle lipid content determined by Oil O Red staining and from glycogen content determined by colorimetric assay.Liver & muscle regulatory pathways. Total gene expression will be assessed in liver and semitendinosus samples frozen at harvest using RNAseq. Differential expression of genes including those for cytokine signaling, insulin signaling, and glucose metabolism will be detected. Western immunoblot will be used to analyze protein content for pathway components indicated by gene expression.Objective 2. Determine the benefits of mitigating heightened inflammation on behavioral changes predictive of poor welfare in heat-stressed lambs with high adiposity. Continuous behavioral assessments. Behaviors with the potential to predict compromised welfare will be assessed continuously with the NUtrack Livestock Monitoring System. Specific behaviors include the frequency and amount of time spent standing, laying, eating, drinking, and engaging in-pen environmental enrichment objects each day. Quantitative behavioral outputs will be correlated with physiological biomarkers of stress.Lameness score. Lambs will be assessed for signs of lameness using the NAMI mobility scoring system. Visual assessments will be performed daily, and lameness scores will be correlated to veterinary diagnostic findings and to stress biomarkers.Panting score. Visual inspections for respiratory distress will be performed using the Mader scoring system.