Heat Stress: A Serious Disruptor of the Reproductive Physiology of Dairy Cows

Heat-Stress Impacts on Developing Bovine Oocytes: Unraveling Epigenetic Changes, Oxidative Stress, and Developmental Resilience

Extreme temperature during summer may lead to heat stress in cattle and compromise their productivity. It also poses detrimental impacts on the developmental capacity of bovine budding oocytes, which halt their fertility. To mitigate the adverse effects of heat stress, it is necessary to investigate the mechanisms through which it affects the developmental capacity of oocytes. The primary goal of this study was to investigate the impact of heat stress on the epigenetic modifications in bovine oocytes and embryos, as well as on oocyte developmental capacity, reactive oxygen species, mitochondrial membrane potential, apoptosis, transzonal projections, and gene expression levels. Our results showed that heat stress significantly reduced the expression levels of the epigenetic modifications from histone H1, histone H2A, histone H2B, histone H4, DNA methylation, and DNA hydroxymethylation at all stages of the oocyte and embryo. Similarly, heat stress significantly reduced cleavage rate, blastocyst rate, oocyte mitochondrial-membrane potential level, adenosine-triphosphate (ATP) level, mitochondrial DNA copy number, and transzonal projection level. It was also found that heat stress affected mitochondrial distribution in oocytes and significantly increased reactive oxygen species, apoptosis levels and mitochondrial autophagy levels. Our findings suggest that heat stress significantly impacts the expression levels of genes related to oocyte developmental ability, the cytoskeleton, mitochondrial function, and epigenetic modification, lowering their competence during the summer season.

miR-425-5p Regulates Proliferation of Bovine Mammary Epithelial Cells by Targeting TOB2

In recent years, rising temperatures have caused heat stress (HS), which has had a significant impact on livestock production and growth, presenting considerable challenges to the agricultural industry. Research has shown that miR-425-5p regulates cellular proliferation in organisms. However, the specific role of miR-425-5p in bovine mammary epithelial cells (BMECs) remains to be determined. The aim of this study was to investigate the potential of miR-425-5p in alleviating the HS-induced proliferation stagnation in BMECs. The results showed that the expression of miR-425-5p significantly decreased when BMEC were exposed to HS. However, the overexpression of miR-425-5p effectively alleviated the inhibitory effect of HS on BMEC proliferation. Furthermore, RNA sequencing analysis revealed 753 differentially expressed genes (DEGs), comprising 361 upregulated and 392 downregulated genes. Some of these genes were associated with proliferation and thermogenesis through enrichment analyses. Further experimentation revealed that TOB2, which acts as a target gene of miR-425-5p, is involved in the regulatory mechanism of BMEC proliferation. In summary, this study suggests that miR-425-5p can promote the proliferation of BMECs by regulating TOB2. The miR-425-5p/TOB2 axis may represent a potential pathway through which miR-425-5p ameliorates the proliferation stagnation of BMECs induced by HS.

Multiview Monitoring of Individual Cattle Behavior Based on Action Recognition in Closed Barns Using Deep Learning

Cattle behavior recognition is essential for monitoring their health and welfare. Existing techniques for behavior recognition in closed barns typically rely on direct observation to detect changes using wearable devices or surveillance cameras. While promising progress has been made in this field, monitoring individual cattle, especially those with similar visual characteristics, remains challenging due to numerous factors such as occlusion, scale variations, and pose changes. Accurate and consistent individual identification over time is therefore essential to overcome these challenges. To address this issue, this paper introduces an approach for multiview monitoring of individual cattle behavior based on action recognition using video data. The proposed system takes an image sequence as input and utilizes a detector to identify hierarchical actions categorized as part and individual actions. These regions of interest are then inputted into a tracking and identification mechanism, enabling the system to continuously track each individual in the scene and assign them a unique identification number. By implementing this approach, cattle behavior is continuously monitored, and statistical analysis is conducted to assess changes in behavior in the time domain. The effectiveness of the proposed framework is demonstrated through quantitative and qualitative experimental results obtained from our Hanwoo cattle video database. Overall, this study tackles the challenges encountered in real farm indoor scenarios, capturing spatiotemporal information and enabling automatic recognition of cattle behavior for precision livestock farming.