Negative effects of heat stress on ovarian tissue in female rabbit

Negative effect of seasonal heat stress on testis morphology and transcriptomes in Angora rabbit

BACKGROUND

The temperature of testes exposed to hyperthermic conditions can affect livestock reproductive performance. This study aimed to explore the difference in semen quality, testicular morphological structure, and gene expression profiles of testes of Angora rabbits in spring (no heat stress), summer (intense heat stress), and autumn (no heat stress) seasons.

RESULTS

Heat stress during summer significantly reduced semen quality and damaged testicular morphology and spermatogenesis, which recovered to normal levels in autumn, although semen quality recovery was notably slow. RNA-Seq analysis showed that the expression levels of 8703 genes changed significantly in summer, but their expression levels in autumn returned to those in spring, which was consistent with the testicular morphology analysis results in different seasons. Enrichment analysis revealed that the DEGs were primarily associated with spermatogenesis, sperm motility, spermatid development, cell death, regulation of apoptotic processes, and responses to external stimuli. The MAPK, Rap1, TNF, Ras, Apoptosis, and Wnt signaling pathways regulated reproduction under heat stress. In addition, minimal variations in testicular morphology and gene expression profiles were observed between autumn and spring. Gene expression pattern analysis showed that genes with high expression in summer mainly participated in the regulation of cell apoptosis, immunity, and response to heat stress, whereas genes with low expression in summer mainly participated in the regulation of spermatogenesis.

CONCLUSIONS

This study investigated the influence of different seasons on the reproductive performance of male Angora rabbits and provided initial insights into the molecular regulatory mechanisms underlying the testicular response to heat stress during summer.

Physio-metabolic response, immune function, epigenetic markers, and reproductive performance of rabbits under environmental stress: the mitigating role of boswellia essential oil nanoemulsion

Global warming poses a significant threat to reproductive health of rabbits. Sustainable nutritional strategies are crucial for ensuring rabbit production and maintaining food security under these challenging conditions. This study sought to assess the protective benefits of dietary boswellia essential oil nano-emulsion (BEON) against oxidative stress, immune dysregulation, ferroptosis, and organ damage in female rabbits exposed to severe thermal stress. A total of 120 female rabbits were divided into four groups of 30 rabbits each. The rabbits were fed a basal diet supplemented with 0 (BEON0), 0.25 (BEON0.25), 0.5 (BEON0.5), and 1.0 (BEON1.0) mL of BEON per kilogram of diet. Results demonstrated that the BEON1.0 group exhibited significantly higher levels of IgG, superoxide dismutase (SOD), and glutathione peroxidase (GPx), while the BEON0.25 group showed elevated levels of IgM, catalase, and total antioxidant capacity (TAC) (P < 0.05). All BEON treatments significantly reduced malondialdehyde (MDA) levels (P < 0.01). Serum levels of progesterone, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) were significantly elevated in the BEON0.5 and BEON1.0 groups compared to the control group (P < 0.01). A significant decrease in adipokine levels was observed in all BEON-supplemented groups compared to the control group (P < 0.05). All BEON groups demonstrated a modulation of ferroptosis pathways, characterized by decreased heat shock protein 70 (HSP70) expression and upregulated expression of glutathione peroxidase 4 (GPX4) and cystine transporter solute carrier 7A11 (SLC7A11) in ovarian tissues (P < 0.01). Furthermore, DNA methyltransferase 1 (DNMT1) expression increased in a dose-dependent manner with increasing BEON supplementation. Histological analysis revealed an improvement in the architecture of the liver, uterine horns, and ovarian tissues in rabbits fed BEON. Integrating BEON at doses of 0.5-1.0 mL/kg diet significantly improved reproductive performance in stressed female rabbits. PCA and correlation analyses demonstrated a positive correlation between BEON supplementation and immune function, reproductive hormone levels, and antioxidant status, while a negative correlation was observed with MDA and adipokine concentrations in rabbit serum. In conclusion, BEON supplementation demonstrates promise as a sustainable nutritional strategy for the rabbit industry, particularly in mitigating the challenges posed by global warming.

Impact of Heat Stress on Oocyte Developmental Competence and Pre-Implantation Embryo Viability in Cattle

Rectal and vaginal temperatures are utilised in both in vivo and in vitro models to study the effects of heat stress on oocyte competence and embryo viability in cattle. However, uterine temperature increases by only 0.5 °C in heat-stressed cows, significantly lower than simulated increases in in vitro models. Temperature variations within oviducts and ovarian follicles during heat stress are poorly understood or unavailable, and evidence is lacking that oocytes and pre-implantation embryos experience mild (40 °C) or severe (41 °C) heat stress inside the ovarian follicle and the oviduct and uterus, respectively. Gathering detailed temperature data from the reproductive tract and follicles is crucial to accurately assess oocyte competence and embryo viability under realistic heat stress conditions. Potential harm from heat stress on oocytes and embryos may result from reduced nutrient availability (e.g., diminished blood flow to the reproductive tract) or other unidentified mechanisms affecting tissue function rather than direct thermal effects. Refining in vivo stress models in cattle is essential to accurately identify animals truly experiencing heat stress, rather than assuming heat stress exposure as done in most studies. This will improve model reliability and aid in the selection of heat-tolerant animals.

Melatonin administration during the first half of pregnancy improves physiological response and reproductive performance of rabbits under heat stress conditions

Context Melatonin may have a heat-stress-alleviating role during pregnancy. Aims To investigate the effects of melatonin administration during the first half of pregnancy on heat-tolerance capacity and pregnancy outputs of naturally heat-stressed rabbits. Methods Forty female rabbits were stratified equally into two experimental groups and daily received 1mg melatonin/kg body weight or not (control) for 15 consecutive days post-insemination. Heat tolerance indices, hormone profile, ovarian structures, and fetal loss were determined. Key results Treatment with melatonin significantly decreased respiration rate and rectal temperature, improved concentrations of nitric oxide, and tended to decrease malondialdehyde concentrations (P =0.064) compared to control. Melatonin treatment significantly increased concentrations of high-density lipoprotein, oestradiol, and progesterone compared to control. No significant differences in the numbers of visible ovarian follicles, corpora lutea, and total implantation sites on day 18 of pregnancy were observed between experimental groups. However, melatonin treatment significantly reduced the number of absorbed implantation sites and significantly improved amniotic fluid volume and conception rate compared to control. Conclusions Melatonin administration during the first half of pregnancy can improve reproductive performance of heat-stressed female rabbits. Implications Melatonin can improve fetal survivability via improving heat-tolerance capacity of does and steroidogenesis.

Mogroside V alleviates the heat stress-induced disruption of the porcine oocyte in vitro maturation

Heat stress (HS) is a stressor that negatively affect female reproduction. Specially, oocytes are very sensitive to HS. It has been demonstrated that some active compounds can protect oocyte from HS. We previously found that Mogroside V (MV), extracted from Siraitia grosvenorii (Luo Han Guo), can protect oocyte from many kinds of stresses. However, how MV alleviates HS-induced disruption of oocyte maturation remains unknown. In this study, we treated the HS-induced porcine oocytes with MV to examine their maturation and quality. Our findings demonstrate that MV can effectively alleviate HS-induced porcine oocyte abnormal cumulus cell expansion, decrease of first polar body extrusion rate, spindle assembly and chromosome separation abnormalities, indicating MV attenuates oocyte mature defects. We further observed that MV can effectively alleviate HS-induced cortical granule distribution abnormality and decrease of blastocyst formation rate after parthenogenesis activation. In addition, MV treatment reversed mitochondrial dysfunction and lipid droplet content decrease, reduced reactive oxygen species levels, early apoptosis and DNA damage in porcine oocytes after HS. Collectively, this study suggests that MV can effectively protect porcine oocytes from HS.

miR-196a Promotes Proliferation of Mammary Epithelial Cells by Targeting CDKN1B

Heat stress (HS) has become one of the key challenges faced by the dairy industry due to global warming. Studies have reported that miR-196a may exert a role in the organism's response to HS, enhancing cell proliferation and mitigating cellular stress. However, its specific role in bovine mammary epithelial cells (BMECs) remains to be elucidated. In this study, we aimed to investigate whether miR-196a could protect BMECs against proliferation arrest induced by HS and explore its potential underlying mechanism. In this research, we developed an HS model for BMECs and observed a significant suppression of cell proliferation as well as a significant decrease in miR-196a expression when BMECs were exposed to HS. Importantly, when miR-196a was overexpressed, it alleviated the inhibitory effect of HS on cell proliferation. We conducted RNA-seq and identified 105 differentially expressed genes (DEGs). Some of these DEGs were associated with pathways related to thermogenesis and proliferation. Through RT-qPCR, Western blotting, and dual-luciferase reporter assays, we identified CDKN1B as a target gene of miR-196a. In summary, our findings highlight that miR-196a may promote BMEC proliferation by inhibiting CDKN1B and suggest that the miR-196a/CDKN1B axis may be a potential pathway by which miR-196a alleviates heat-stress-induced proliferation arrest in BMECs.

Ramifications of Heat Stress on Rabbit Production and Role of Nutraceuticals in Alleviating Its Negative Impacts: An Updated Review

Heat stress has become a widespread concern worldwide, which is a major environmental stress that causes substantial economic loss in the rabbit industry. Compared to other agricultural animals, rabbits are more sensitive to heat stress as they have fewer sweat glands and a thicker coat of fur, increasing the heat dissipation complexity. Thus, heat stress hurts rabbits' productivity, meat quality, reproductive performance, antioxidative properties, immune responsiveness, intestinal histomorphology, and microbiome. Nutraceuticals include vitamins, minerals, antioxidants, organic acids, fatty acids, probiotics, prebiotics, synbiotics, enzymes, and medicinal plants due to the possible impacts on maintaining common biological situations, strengthening immune response, and preventing illness, which ultimately led to an increase in productivity. Nutraceuticals have recently attracted a lot of attention to alleviate the adverse impacts of heat stress in rabbit farms. The objective of the current review is to provide acquaintance with the recent findings about the impact of heat stress on rabbit productivity and the advantages of dietary supplementation of nutraceuticals in mitigating it.