• Energy Research

Heat stress and cold stress have a negative influence on cattle welfare and productivity. There have been some studies investigating the influence of cold stress on cattle, however the emphasis within this review is the influence of heat stress on cattle. The impact of hot weather on cattle is of increasing importance due to the changing global environment. Heat stress is a worldwide phenomenon that is associated with reduced animal productivity and welfare, particularly during the summer months. Animal responses to their thermal environment are extremely varied, however, it is clear that the thermal environment influences the health, productivity, and welfare of cattle. Whilst knowledge continues to be developed, managing livestock to reduce the negative impact of hot climatic conditions remains somewhat challenging. This review provides an overview of the impact of heat stress on production and reproduction in bovines.

Heat stress and cold stress have a negative influence on cattle welfare and productivity. There have been some studies investigating the influence of cold stress on cattle, however the emphasis within this review is the influence of heat stress on cattle. The impact of hot weather on cattle is of increasing importance due to the changing global environment. Heat stress is a worldwide phenomenon that is associated with reduced animal productivity and welfare, particularly during the summer months. Animal responses to their thermal environment are extremely varied, however, it is clear that the thermal environment influences the health, productivity, and welfare of cattle. Whilst knowledge continues to be developed, managing livestock to reduce the negative impact of hot climatic conditions remains somewhat challenging. This review provides an overview of the impact of heat stress on production and reproduction in bovines.

Heat stress impacts ruminant livestock production on varied levels in this alarming climate breakdown scenario. The drastic effects of the global climate change-associated heat stress in ruminant livestock demands constructive evaluation of animal performance bordering on effective monitoring systems. In this climate-smart digital age, adoption of advanced and developing Artificial Intelligence (AI) technologies is gaining traction for efficient heat stress management. AI has widely penetrated the climate sensitive ruminant livestock sector due to its promising and plausible scope in assessing production risks and the climate resilience of ruminant livestock. Significant improvement has been achieved alongside the adoption of novel AI algorithms to evaluate the performance of ruminant livestock. These AI-powered tools have the robustness and competence to expand the evaluation of animal performance and help in minimising the production losses associated with heat stress in ruminant livestock. Advanced heat stress management through automated monitoring of heat stress in ruminant livestock based on behaviour, physiology and animal health responses have been widely accepted due to the evolution of technologies like machine learning (ML), neural networks and deep learning (DL). The AI-enabled tools involving automated data collection, pre-processing, data wrangling, development of appropriate algorithms, and deployment of models assist the livestock producers in decision-making based on real-time monitoring and act as early-stage warning systems to forecast disease dynamics based on prediction models. Due to the convincing performance, precision, and accuracy of AI models, the climate-smart livestock production imbibes AI technologies for scaled use in the successful reducing of heat stress in ruminant livestock, thereby ensuring sustainable livestock production and safeguarding the global economy.

Heat stress impacts ruminant livestock production on varied levels in this alarming climate breakdown scenario. The drastic effects of the global climate change-associated heat stress in ruminant livestock demands constructive evaluation of animal performance bordering on effective monitoring systems. In this climate-smart digital age, adoption of advanced and developing Artificial Intelligence (AI) technologies is gaining traction for efficient heat stress management. AI has widely penetrated the climate sensitive ruminant livestock sector due to its promising and plausible scope in assessing production risks and the climate resilience of ruminant livestock. Significant improvement has been achieved alongside the adoption of novel AI algorithms to evaluate the performance of ruminant livestock. These AI-powered tools have the robustness and competence to expand the evaluation of animal performance and help in minimising the production losses associated with heat stress in ruminant livestock. Advanced heat stress management through automated monitoring of heat stress in ruminant livestock based on behaviour, physiology and animal health responses have been widely accepted due to the evolution of technologies like machine learning (ML), neural networks and deep learning (DL). The AI-enabled tools involving automated data collection, pre-processing, data wrangling, development of appropriate algorithms, and deployment of models assist the livestock producers in decision-making based on real-time monitoring and act as early-stage warning systems to forecast disease dynamics based on prediction models. Due to the convincing performance, precision, and accuracy of AI models, the climate-smart livestock production imbibes AI technologies for scaled use in the successful reducing of heat stress in ruminant livestock, thereby ensuring sustainable livestock production and safeguarding the global economy.

Heat stress causes functional and metabolic alterations in different cells and tissues. There are several pathomorphological changes and biomarkers associated with head load in adaptive and productive organs of livestock. Heat stress-induced histopathological alterations in livestock were categorized as degenerative changes (fatty degeneration, steatosis, hydropic degeneration), necrosis (pyknosis, fibrosis), circulatory disturbances (hyperemia, edema, hemorrhage, congestion, thrombosis, ischemia), growth disturbances (hyperplasia, atrophy) and focal/diffuse inflammation (vascular changes, exudation). Upon immunohistochemical analysis, the biomarkers identified in growth-related organs were HSP70, HSP60, GABA, GABAAR, GABABR, HSP90, GnRH, LH, FSH, m6A, Nrf2, and C/EBPβ. The biomarkers in the reproductive organs were HSP70, Bax, Bcl-2, GABA, GABAAR, GABABR, Caspase-3, HSP90, HSPB9, HSPB10, HSF1, HSP40, T, E2, Cyt-C, CAT, BCL2L1, and VEGF. The identified biomarkers in the immune organs were CD3+ T cells, CD4+ T cells, CD8+ T cells, HSP70, and Bcl-2. All these biomarkers could serve as reliable variables in heat stress assessment in livestock. Further, HSP70, HSP90, HSP60, NPY, HSP27, Bcl-2, NF-κB, AQP2, Insulin, CD3+ T cells, CD4+ T cells, CD172a, EGF, AQP1, AQP3, AQP4, AQP5, CRYAB, GHR, 5-HT, CCK, and GLP-1 are heat stress-related biomarkers in adaptive organs that help in assessing the climate resilience of a livestock species and improving understanding about adaptive mechanisms. Among these biomarkers, HSP70 was established to be the ideal cellular biomarker for scaling heat response in livestock. Thus, examining heat-stressed organ histopathology and identifying cellular markers by immunohistochemistry may lay the foundation for screening climate-resilient livestock breeds in the challenging climatic scenario. Further, such an approach could help in developing concepts to combat the detrimental consequences of heat stress to ensure sustainability in livestock production.

Heat stress causes functional and metabolic alterations in different cells and tissues. There are several pathomorphological changes and biomarkers associated with head load in adaptive and productive organs of livestock. Heat stress-induced histopathological alterations in livestock were categorized as degenerative changes (fatty degeneration, steatosis, hydropic degeneration), necrosis (pyknosis, fibrosis), circulatory disturbances (hyperemia, edema, hemorrhage, congestion, thrombosis, ischemia), growth disturbances (hyperplasia, atrophy) and focal/diffuse inflammation (vascular changes, exudation). Upon immunohistochemical analysis, the biomarkers identified in growth-related organs were HSP70, HSP60, GABA, GABAAR, GABABR, HSP90, GnRH, LH, FSH, m6A, Nrf2, and C/EBPβ. The biomarkers in the reproductive organs were HSP70, Bax, Bcl-2, GABA, GABAAR, GABABR, Caspase-3, HSP90, HSPB9, HSPB10, HSF1, HSP40, T, E2, Cyt-C, CAT, BCL2L1, and VEGF. The identified biomarkers in the immune organs were CD3+ T cells, CD4+ T cells, CD8+ T cells, HSP70, and Bcl-2. All these biomarkers could serve as reliable variables in heat stress assessment in livestock. Further, HSP70, HSP90, HSP60, NPY, HSP27, Bcl-2, NF-κB, AQP2, Insulin, CD3+ T cells, CD4+ T cells, CD172a, EGF, AQP1, AQP3, AQP4, AQP5, CRYAB, GHR, 5-HT, CCK, and GLP-1 are heat stress-related biomarkers in adaptive organs that help in assessing the climate resilience of a livestock species and improving understanding about adaptive mechanisms. Among these biomarkers, HSP70 was established to be the ideal cellular biomarker for scaling heat response in livestock. Thus, examining heat-stressed organ histopathology and identifying cellular markers by immunohistochemistry may lay the foundation for screening climate-resilient livestock breeds in the challenging climatic scenario. Further, such an approach could help in developing concepts to combat the detrimental consequences of heat stress to ensure sustainability in livestock production.

AbstractThe adaptive potential of livestock under a warming climate is increasingly relevant in relation to the growing pressure of global food security. Studies on heat tolerance demonstrate the interplay of adaptation and acclimatization in functional traits, for example, a reduction in body size and enhanced tolerance in response to a warming climate. However, current lack of understanding of functional traits and phylogenetic history among phenotypically distinct populations constrains predictions of climate change impact. Here, we demonstrate evidence of parallel evolution in adaptive tolerance to heat stress in dwarf cattle breeds (DCB, Bos taurus indicus) and compare their thermoregulatory responses with those in standard size cattle breeds (SCB, crossbred, Bos taurus indicus × Bos taurus taurus). We measured vital physiological, hematological, biochemical, and gene expression changes in DCB and SCB and compared the molecular phylogeny using mitochondrial genome (mitogenome) analysis. Our results show that SCB can acclimatize in the short term to higher temperatures but reach their tolerance limit under prevailing tropical conditions, while DCB is adapted to the warmer climate. Increased hemoglobin concentration, reduced cellular size, and smaller body size enhance thermal tolerance. Mitogenome analysis revealed that different lineages of DCB have evolved reduced size independently, as a parallel adaptation to heat stress. The results illustrate mechanistic ways of dwarfing, body size‐dependent tolerance, and differential fitness in a large mammal species under harsh field conditions, providing a background for comparing similar populations during global climate change. These demonstrate the value of studies combining functional, physiological, and evolutionary approaches to delineate adaptive potential and plasticity in domestic species. We thus highlight the value of locally adapted breeds as a reservoir of genetic variation contributing to the global domestic genetic resource pool that will become increasingly important for livestock production systems under a warming climate.