Background: Heat stress is known to affect follicular dynamics, oocyte maturation, and fertilization by impairing steroidogenic ability and viability of bovine granulosa cell (bGCs). The present study explored the physiological and molecular response of bGCs to different heat stress intensitiesin-vitro. We exposed the primary bGCs to heat stress (HS) at 39 °C, 40 °C and 41 °C along with control samples (38 °C) for 2 h. To evaluate the impact of heat stress on bGCs, severalin vitrocellular parameters including cell apoptosis, intracellular reactive oxygen species (ROS) accumulation andHSP70kinetics were assessed by flow cytometry, florescence microscopy and western blot, respectively. Furthermore, the ELISA was performed to confirm the 17β-estradiol (E₂) and progesterone (P₄) levels. In addition, the RNA sequencing (RNA-Seq) method was used to get the molecular based response of bGCs to different heat treatments.Results: Our findings revealed that the HS significantly decreased the cell viability, E₂and P₄levels in bGCs, whereas, increased the cellular apoptosis and ROS. Moreover, the RNA-Seq experiments showed that all the treatments (39 °C, 40 °C and 41 °C) significantly regulated many differentially expressed genes (DEGs) i.e.BCL2L1, STAR, CYP11A1, CASP3, SOD2, HSPA13, andMAPK8IP1and pathways associated with heat stress, apoptosis, steroidogenesis, and oxidative stress. Conclusively, our data demonstrated that the impact of 40 °C treatment was comparatively detrimental for cell viability, apoptosis and ROS accumulation. Notably, a similar trend of gene expression was reported by RT-qPCR for RNA-seq data.Conclusions: Our study presented a worthy strategy for the first time to characterize the cellular and transcriptomic adaptation of bGCs to heat stress (39, 40 and 41 °C)in-vitro. The results infer that these genes and pathways reported in present study could be useful candidates/indicators for heat stress research in dairy cattle. Moreover, the established model of bGCs to heat stress in the current study provides an appropriate platform to understand the mechanism of how heat-stressed bGCs can affect the quality of oocytes and developing embryo.

Genetic selection for improved climatic resilience is paramount to increase the long-term sustainability of high-producing dairy cattle, especially in face of climate change. Various physiological indicators, such as rectal temperature (RT), respiration rate score (RR), and drooling score (DS), can be used to genetically identify animals with more effective coping mechanisms in response to heat stress events. In this study, we investigated genetic parameters for RT, RR (score from 1-3), and DS (score from 1-3). Furthermore, we assessed the genetic relationship among these indicators and other economically important traits for the dairy cattle industry. After data editing, 59,265 (RT), 30,290 (RR), and 30,421 (DS) records from 13,592 lactating Holstein cows were used for the analyses. Variance components were estimated based on a multiple-trait repeatability animal model. The heritability ± standard error estimate for RT, RR, and DS was 0.06 ± 0.01, 0.04 ± 0.01, and 0.02 ± 0.01, respectively, whereas their repeatability was 0.19, 0.14, and 0.14, respectively. Moderate genetic correlations of RR with RT and DS (0.26 ± 0.11 and 0.25 ± 0.16) and nonsignificant correlation between RT and DS (-0.11 ± 0.14) were observed. Furthermore, the approximate genetic correlations between RT, RR, and DS with 12 production, 29 conformation, 5 fertility and reproduction, 5 health, and 9 longevity-indicator traits were assessed. In general, the approximate genetic correlations calculated were low to moderate. In summary, 3 physiological indicators of heat stress response were measured in a large number of animals and shown to be lowly heritable. There is a value in developing a selection index including all the 3 indicators to improve heat tolerance in dairy cattle. All the unfavorable genetic relationships observed between heat tolerance and other economically important traits can be accounted for in a selection index to enable improved climatic resilience while also maintaining or increasing productivity in Holstein cattle.

Background: Mastitis in dairy cows caused byStaphylococcus aureusis a major problem hindering economic growth in dairy farms worldwide. It is difficult to prevent or eliminate due to its asymptomatic nature and long persistence of infection. Although transcriptomic responses of bovine mammary gland cells to pathogens that cause mastitis have been studied, the common responses of peripheral blood leukocytes toS. aureusinfection across two consecutive generations of dairy cattle have not been investigated.Methods: In the current study, RNA-Seq was used to profile the transcriptomes of peripheral blood leukocytes sampled fromS. aureus-infected mothers and theirS. aureus-infected daughters, and also healthy non-infected mothers and their healthy daughters. Differential gene expression was evaluated as follows: 1)S. aureus-infected cows versus healthy non-infected cows (S vs. H, which include all the mothers and daughters), 2)S. aureus-infected mothers versus healthy non-infected mothers (SM vs. HM), and 3)S. aureus-infected daughters versus healthy non-infected daughters (SMD vs. HMD).Results: Analysis of all identified expressed genes in the four groups (SM, SMD, HM, and HMD) showed thatEPOR,IL9,IFNL3,CCL26,IL26were exclusively expressed in both the HM and HMD groups, and that they were significantly (P < 0.05) enriched for the cytokine-cytokine receptor interaction pathway. A total of 17, 13 and 10 differentially expressed genes (DEGs) (FDRP_adj.< 0.1 and |FC| > 1.2) were detected in the three comparisons, respectively. DEGs withP < 0.05 and |FC| > 2 were used for functional enrichment analyses. For the S vs. H comparison, DEGs detected includedCCL20,IL13andMMP3, which are associated with the IL-17 signaling pathway. In the SM vs. HM and SMD vs. HMD comparisons, five (BLA-DQB,C1R,C2,FCGR1A, andKRT10) and six (BLA-DQB,C3AR1,CFI,FCAR,FCGR3A, andLOC10498484) genes, respectively, were involved in theS. aureusinfection pathway.Conclusions: Our study provides insights into the transcriptomic responses of bovine peripheral blood leukocytes across two generations of cattle naturally infected withS. aureus. The genes highlighted in this study could serve as expression biomarkers for mastitis and may also contain sequence variation that can be used for genetic improvement of dairy cattle for resilience to mastitis.

Heat stress (HS) is challenging in humans and animals as it is a complicated regulatory mechanism. This prompted us to characterize the physiological and molecular responses of a HS-animal model. In this study, a rat model system was developed by using three temperature treatments (40 ℃, 42 ℃, and 43 ℃) and sixteen biochemical indicators in blood at 42 ℃ for 30 min (H30), 60 min (H60), and 120 min (H120). In addition, transcriptomic profiling was carried out in H120-rats’ blood, liver, and adrenal gland samples for detection of the genes of interest. Our findings demonstrated that the adrenocorticotropic hormone, catalase, prolactin, growth hormone, and lactic acid have significant spatiotemporal variation in the H120-rats as compared with the control. Furthermore, through transcriptomic screening, we documented a high ratio of differentially expressed genes (DEGs) in adrenal glands, liver, and blood, respectively. Among them, Nup153, Plxnb2, Stx7, Hspa9, Chordc1, Pde4d, Gm2α, and Rnf125 were associated with the regulation of HS and immune response processes. Notably, 36 and 314 of DEGs in blood and adrenal glands were detected in the composition of the extracellular exosome, respectively. Furthermore, the correlation analysis between gene transcripts and biochemical indicator levels identified the Lgals3, S1006, Fn1, F2, and Kng1l1 as key candidate genes for HS encoding extracellular exosomal proteins. On the basis of our results, it was concluded that the current rat model provides a molecular basis for future research in HS resistance in humans and livestock.

The periparturient period is the period from three weeks before calving to three weeks post-calving. This period is important in terms of health, productivity and profitability, and is fundamental to successful lactation. During this period, the animal experiences stress because of hormonal changes due to pregnancy and the significant rise in milk production. In addition, a negative energy balance usually occurs, because the demand for nutrients to sustain milk production increases by more than the nutrient supply during the periparturient period. The immunity of dairy cattle is suppressed around parturition, which increases their susceptibility to infections. Special care regarding nutrition can reduce the risks of metabolism and immunity depression, which dairy cattle face during the periparturient span. Folic acid is relevant in this regard because of its critical role in the metabolism to maintain lactational performance and to improve health. Being a donor of one-carbon units, folic acid has a vital role in DNA and RNA biosynthesis. Generally, the folic acid requirements of dairy cattle can be met by the microbial synthesis in the rumen; however, in special cases, such as during the periparturient period, the requirement for this vitamin strictly increases. Vitamin B12 also has a critical role in the metabolism as a coenzyme of the enzyme methionine synthase for the transfer of a methyl group from folic acid to homocysteine for the regeneration of methionine. In the current review, we highlight the issues facing periparturient dairy cattle, and relevant knowledge and practices, and point out future research directions for utilization of the associated vitamins in ruminants, especially during the periparturient period.