Poster Presentation 23rd International Society of Magnetic Resonance Conference 2023

NMR-based metabolomics and clinical biochemistry analysis of severe and moderate heat stress in Angus steers (#247)

Alexandra Gloria 1 2 , Gene Wijffels 3 , Megan Sullivan 4 , John Gaughan 4 , Horst Joachim Schirra 1 2 5
  1. Centre for Advanced Imaging, The University of Queensland, St Lucia, QLD, Australia
  2. Griffith Institute for Drug Discovery, Griffith University, Nathan, QLD, Australia
  3. Agriculture and Food, Commonwealth Scientific and Industrial Research Organisation (CSIRO), St Lucia, QLD, Australia
  4. School of Agriculture and Food Sustainability, The University of Queensland, Gatton, QLD, Australia
  5. School of Environment and Science, Griffith University, Nathan, QLD, Australia

Heat stress is an ongoing issue in the agriculture industry and animal production. In mammals, extreme heat stress causes catastrophic failures, including heat stroke and acute renal failure. Efficient body thermoregulation mechanisms are necessary to combat heat load. Black Angus steers are important for beef production, but they are more susceptible to heat stress due to their acclimation to temperate regions. It is important to understand the metabolic changes caused by heat stress in Angus steers to develop methods of offsetting its impact.

We subjected grain-fed Angus steers to two different heat load levels: severe (maximum Ta between 40°C-36°C over seven days) and moderate (maximum Ta 35°C over seven days). For a detailed biological analysis via a systems-wide overview, we combined NMR-based metabolomics and clinical biochemistry. Plasma 1H-NMR Carr-Purcell-Meiboom-Gill (CPMG) spectra were acquired for multivariate statistical analysis, and 2D 1H-13C heteronuclear single quantum coherence (HSQC) spectra were used to identify metabolites that changed significantly depending on the treatment level. Furthermore, significant changes in clinical biochemistry parameter levels in the plasma samples were identified.

During a severe heat load, steers drastically reduce their metabolic rate to reduce endogenous heat. Changes in energy metabolites, such as glucose and lactate, suggest gluconeogenesis is not occurring, while acetate and β-hydroxybutyrate suggest the use of ketone bodies as fuel. Furthermore, increased creatinine suggests a decrease in renal function. This mechanism contrasts with a moderate heat load, where steers experience slight metabolic perturbations, such as nutrient partitioning and mobilisation of fatty acids through increased levels of non-esterified fatty acids and triglycerides. When recovering from either level of heat stress, steers’ metabolic states do not fully return to baseline, particularly after a severe heat load. Increased glucose and β-hydroxybutrate suggest recurring changes in energy metabolism, implying a longer recovery period is necessary after a high heat load.