Animal Molecular Breeding 2024, Vol.14, No.3, 196-206 http://animalscipublisher.com/index.php/amb 199 Figure 1 Relative abundance of serum microRNA (miRNA) as assessed by quantitative PCR in high (HBCS; n=15) and normal body condition (NBCS; n=15) dairy cows on d-49, -7, 3, 21 and 84 relative to parturition (Adopted from Webb et al., 2020) Image caption: Data are given as means±SEM. Different uppercase letters (A-C) illustrate differences (P<0.05) between time points within HBCS; Different lowercase letters (a-c) illustrate differences (P<0.05) between time points within NBCS. Differences between HBCS and NBCS within 1 time point are labeled with * (0.01<P< 0.05) or ** (P<0.01). Trends (0.05<P<0.1) are labeled with hashtags (#); The dashed line indicates calving (Adopted from Webb et al., 2020) 4.4 Comparative approaches: normal vs. heat-stressed conditions Comparative approaches involve analyzing gene expression profiles in cattle under normal and heat-stressed conditions to identify stress-responsive genes and pathways. Studies have shown significant differences in the expression of miRNAs and their target genes between heat-stressed and non-heat-stressed cattle. For example, miRNA profiling in Holstein cows under summer heat stress revealed differential expression of miRNAs associated with progesterone biosynthesis and immune responses, suggesting that pregnant cows are more susceptible to heat stress (Lee et al., 2020). Another study on buffalo heifers demonstrated significant upregulation of heat shock proteins and miRNAs involved in heat tolerance under heat stress conditions (Yadav et al., 2021). These comparative analyses provide valuable insights into the molecular mechanisms underlying heat stress response in dairy cattle (Sigdel et al., 2020). 5 Case Study: Gene Expression Profiles in Heat-Stressed Dairy Cattle 5.1 Overview of the case study This case study investigates the gene expression profiles in dairy cattle subjected to heat stress, a condition that significantly impacts their productivity and overall health. The study focuses on understanding the molecular mechanisms underlying the heat stress response by examining various tissues and biological markers in dairy cows. 5.2 Study design The study employed a multi-faceted approach to analyze gene expression in dairy cattle under heat stress. Different research methodologies were utilized, including RNA sequencing, genome-wide association studies (GWAS), and proteomics. Samples were collected from various tissues such as the hypothalamic-pituitary-mammary gland axis (Figure
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