Effects of heat stress on mammalian reproduction

Synergistic protective effects of 3,4-dihydroxyphenylglycol and hydroxytyrosol in male rats against induced heat stress-induced reproduction damage

Testicular heat stress disrupts spermiogenesis and damages testicular tissue. The study aims to assess 3,4-dihydroxyphenylglycol (DHPG) and hydroxytyrosol (HT) from olive oil as antioxidants to reduce heat-induced testicular damage. Seven groups of 35 male rats were used. Group I got normal saline. Group 2 had HS (43 °C for 20 min/day) and normal saline for 60 days. Groups 3-7 had HS and DHPG/HT doses (0.5 mg/kg DHPG, 1 mg/kg DHPG, 5 mg/kg HT, 0.5 mg/kg DHPG + 5 mg/kg HT, and 1 mg/kg DHPG + 5 mg/kg HT). The evaluation included tests on testicular tissue, sperm quality, oxidative status, gene activity, and fertility after 60 days. After DHPG and HT treatment, sperm motility, viability, and plasma membrane functionality, as well as levels of total antioxidant capacity (TAC), glutathione peroxidase (GPx), superoxide dismutase (SOD), and catalase (CAT), and Bcl-2 gene expression, and in vivo fertility indexes increased. Meanwhile, abnormal morphology and DNA damage decreased, along with levels of glutathione (GSH), nitric oxide (NO), and malondialdehyde (MDA), and Bax, caspase-3, and caspase-9 gene expression, compared to the HS group. The study found that DHPG and HT have a more substantial synergistic effect when used together, improving reproductive health.

Sestrin2 and Sestrin3 protect spermatogenesis against heat-induced meiotic defects†

Heat stress induces testicular oxidative stress, impairs spermatogenesis, and increases the risk of male infertility. Recent studies have highlighted the antioxidative properties of the Sestrins family in reducing cellular oxidative damage. However, the role of Sestrins (Sestrin1, 2, and 3) in the testicular response to heat stress remains unclear. Here, we found that Sestrin2 and 3 were highly expressed in the testis relative to Sestrin1. Then, the Sestrin2-/- and Sestrin3-/- mice were generated by CRISPR/Cas9 to investigate the role of them on spermatogenesis after heat stress. Our data showed that Sestrin2-/- and Sestrin3-/- mice testes exhibited more severe damage manifested by exacerbated loss of germ cells and higher levels of oxidative stress as compared to wild-type counterparts after heat stress. Notably, Sestrin2-/- and Sestrin3-/- mice underwent a remarkable increase in heat-induced spermatocyte apoptosis than that of controls. Furthermore, the transcriptome landscape of spermatocytes and chromosome spreading showed that loss of Sestrin2 and Sestrin3 exacerbated meiotic failure by compromising DNA double-strand breaks repair after heat stress. Taken together, our work demonstrated a critical protective function of Sestrin2 and Sestrin3 in mitigating the impairments of spermatogenesis against heat stress.

Meat quality and safety issues during high temperatures and cutting-edge technologies to mitigate the scenario

Climate change, driven by the natural process of global warming, is a worldwide issue of significant concern because of its adverse effects on livestock output. The increasing trend of environmental temperature surging has drastically affected meat production and meat product quality, hence result in economic losses for the worldwide livestock business. Due to the increasing greenhouse gas emissions, the situation would get prolonged, and heat exposure-related stress is expected to worsen. Heat exposure causes metabolic and physiological disruptions in livestock. Ruminants and monogastric animals are very sensitive to heat stress due to their rate of metabolism, development, and higher production levels. Before slaughter, intense hot weather triggers muscle glycogen breakdown, producing pale, mushy, and exudative meat with less water-holding capacity. Animals exposed to prolonged high temperatures experience a decrease in their muscle glycogen reserves, producing dry, dark, and complex meat with elevated final pH and increased water-holding capacity. Furthermore, heat stress also causes oxidative stresses, especially secondary metabolites from lipid oxidation, severely affects the functionality of proteins, oxidation of proteins, decreasing shelf life, and food safety by promoting exfoliation and bacterial growth. Addressing the heat-related issues to retain the sustainability of the meat sector is an essential task that deserves an inclusive and comprehensive approach. Considering the intensity of the heat stress effects, this review has been designed primarily to examine the consequences of hot environment temperatures and related stresses on the quality and safety of meat and secondarily focus on cutting edge technology to reduce or alleviate the situational impact.

Heat stress at the bicellular stage inhibits sperm cell development and transport into pollen tubes

For successful double fertilization in flowering plants (angiosperms), pollen tubes deliver 2 nonmotile sperm cells toward female gametes (egg and central cell, respectively). Heatwaves, especially during the reproduction period, threaten male gametophyte (pollen) development, resulting in severe yield losses. Using maize (Zea mays) as a crop and grass model system, we found strong seed set reduction when moderate heat stress was applied for 2 d during the uni- and bicellular stages of pollen development. We show that heat stress accelerates pollen development and impairs pollen germination capabilities when applied at the unicellular stage. Heat stress at the bicellular stage impairs sperm cell development and transport into pollen tubes. To understand the course of the latter defects, we used marker lines and analyzed the transcriptomes of isolated sperm cells. Heat stress affected the expression of genes associated with transcription, RNA processing and translation, DNA replication, and the cell cycle. This included the genes encoding centromeric histone 3 (CENH3) and α-tubulin. Most genes that were misregulated encode proteins involved in the transition from metaphase to anaphase during pollen mitosis II. Heat stress also activated spindle assembly check point and meta- to anaphase transition genes in sperm cells. In summary, misregulation of the identified genes during heat stress at the bicellular stage results in sperm cell development and transport defects ultimately leading to sterility.

Artificial intelligence and porcine breeding

Livestock management is evolving into a new era, characterized by the analysis of vast quantities of data (Big Data) collected from both traditional breeding methods and new technologies such as sensors, automated monitoring system, and advanced analytics. Artificial intelligence (A-In), which refers to the capability of machines to mimic human intelligence, including subfields like machine learning and deep learning, is playing a pivotal role in this transformation. A wide array of A-In techniques, successfully employed in various industrial and scientific contexts, are now being integrated into mainstream livestock management practices. In the case of swine breeding, while traditional methods have yielded considerable success, the increasing amount of information requires the adoption of new technologies such as A-In to drive productivity, enhance animal welfare, and reduce environmental impact. Current findings suggest that these techniques have the potential to match or exceed the performance of traditional methods, often being more scalable in terms of efficiency and sustainability within the breeding industry. This review provides insights into the application of A-In in porcine breeding, from the perspectives of both sows (including welfare and reproductive management) and boars (including semen quality and health), and explores new approaches which are already being applied in other species.

Vitamin C Alleviates the Negative Effects of Heat Stress on Reproductive Processes by Regulating Amino Acid Metabolism in Granulosa Cells

Heat stress-induced biochemical alterations in ovarian follicles compromise the function of granulosa cells (GCs) and the developmental competence of oocytes. Summer heat stress can have a far-reaching negative impact on overall fertility and reproductive success. Together with the heat stress, the rise of assisted reproductive technologies (ART), potential confounding hazards of in vitro handling and the absence of systemic body support in ART makes it imperative to study the heat stress ameliorative effects of vitamin C under in vitro conditions. Using in vitro heat stress treatment of 43 °C for two hours in bovine GCs, we studied the effects of vitamin C on cell growth, oxidative stress, apoptosis and cell cycle progression together with a comprehensive metabolomics profiling. This study investigates the molecular milieu underlying the vitamin C (VC)-led alleviation of heat-related disruptions to metabolic processes in bovine GCs. The supplementation of VC ameliorated the detrimental effects of heat stress by reducing oxidative stress and apoptosis while restoring cell proliferation. Normal cell function restoration in treated GCs was demonstrated through the finding of significantly high levels of progesterone. We observed a shift in the metabolome from biosynthesis to catabolism, mostly dominated by the metabolism of amino acids (decreased tryptophan, methionine and tyrosine) and the active TCA cycle through increased Succinic acid. The Glutathione and tryptophan metabolism were important in ameliorating the inflammation and metabolism nexus under heat stress. Two significant enzymes were identified, namely tryptophan 2,3-dioxygenase (TDO2) and mitochondrial phenylalanyl-tRNA synthetase (FARS2). Furthermore, our findings provide insight into the significance of B-complex vitamins in the context of heat stress during VC supplementation. This study underscores the importance of VC supplementation in heat stress and designates multiple metabolic intervention faucets in the context of ameliorating heat stress and enhancing reproductive efficiency.

Habitat type modulates sharp body mass oscillations in cyclic common vole populations

Cyclic rodent populations exhibit pronounced changes in body mass associated with the population cycle phase, long-known as Chitty effect. Although Chitty effect is a common epiphenomenon in both America and Europe, there is still incomplete evidence about the generality of these patterns across the entire range of most species. Moreover, despite decades of research, the underlying factors driving Chitty effect remains poorly understood. Here, we examined the influence of intrinsic and extrinsic factors that may underlie observed patterns in vole size variation in the Iberian common vole Microtus arvalis asturianus. We weighed and measured 2816 adult voles that were captured during 6 trapping periods. Vole numbers and body mass showed strong period- and phase-related variation both in females and males, demonstrating marked Chitty effect in the studied population. Body mass of adult males correlated with body length, evidencing that heavier males are also structurally larger. Statistical models showed that probability of occurrence of large-sized vole (> 37 g) was significantly more likely in reproductive males, during increase and peak phases, and it was modulated by habitat, with crop fields and field margins between crops showing an increased likelihood. We suggest an effect of the habitat on vole body mass mediated by predation.

Developmental programming of the ovarian reserve in livestock

Mammalian females are born with a finite number of follicles in their ovaries that is referred to as the ovarian reserve. There is a large amount of variation between females in the number of antral follicles that they are born with, but this number is positively correlated to size of the ovarian reserve, has a strong repeatability within a female, and a moderate heritability. Although the heritability is moderate, numerous external factors including health, nutrition, ambient temperature, and litter size influence the size and function of the ovarian reserve throughout life. Depletion of the ovarian reserve contributes to reproductive senescence, and genetic and epigenetic factors can lead to a more rapid decline in follicle numbers in some females than others. The relationship of the size of the ovarian reserve to development of the reproductive tract and fertility is generally positive, although some studies report antagonistic associations of these traits. It seems likely that management decisions and environmental factors that result in epigenetic modifications to the genome throughout life may cause variability in the function of ovarian genes that influence fecundity and fertility, leading to differences in reproductive longevity among females born with ovarian reserves of similar size. This review summarizes our current understanding of factors influencing size of the ovarian reserve in cattle, sheep, and pigs and the relationship of the ovarian reserve to reproductive tract development and fertility. It provides strategies to apply this knowledge to improve diagnostics for better assessment of fertility and reproductive longevity in female livestock.

Experimental heatwaves reduce the effectiveness of ejaculates at occupying female reproductive tracts in a model insect

Globally, heatwaves have become more common with hazardous consequences on biological processes. Research using a model insect (Tribolium castaneum) found that 5-day experimental heatwave conditions damaged several aspects of male reproductive biology, while females remained unaffected. However, females' reproductive fitness may still be impacted, as insects typically store sperm from multiple males in specialized organs for prolonged periods. Consequently, using males which produce sperm with green fluorescent protein (GFP)-tagged sperm nuclei, we visualized in vivo whether thermal stress affects the ejaculate occupancy across female storage sites under two scenarios; (i) increasing time since insemination and (ii) in the presence of defending competitor sperm. We reconfirmed that sperm from heatwave-exposed males sired fewer offspring with previously mated females and provided new scenarios for in vivo distributions of heat-stress-exposed males' sperm. Sperm from heatwave-exposed males occupied a smaller area and were at lower densities across the females' storage sites. Generally, sperm occupancy decreased with time since insemination, and sperm from the first male to mate dominated the long-term storage site. Reassuringly, although heated males' ejaculate was less successful in occupying female tracts, they were not lost from female storage at a faster rate and were no worse than control males in their offensive ability to enter storage sites occupied by competitor sperm. Future work should consider the potential site-specificity of factors influencing sperm storage where amenable.

Ameliorative effects of omega-3 and omega-6 on spermatogenesis, testicular antioxidant status and in vivo fertility index in heat-stressed rats

The current study aimed to investigate the use of omega-6 (ω6) or omega-3 (ω3) in reducing heat-induced damage to the testicles. This is due to the known detrimental effects of heat and the potential protective properties of ω6 and ω3. In the study, 48 male rats were divided into eight groups, each containing 6 rats. Group I (control) received normal saline. Group 2 was exposed to high temperatures (43 °C for 20 min/day) and also received normal saline for 60 days. Groups 3-7 underwent identical HS conditions and received varying doses of ω6 or ω3 (0.5 mg/kg DHPG, 1 mg/kg DHPG, 5 mg/kg HT, 0.5 mg/kg DHPG + 5 mg/kg HT, and 1 mg/kg DHPG + 5 mg/kg HT), respectively. After 60 days, various tests were conducted on the testicular tissue, sperm quality, oxidative status, gene activity, and in vivo fertility indexes to evaluate the effects of the treatments. Treatment with ω6 and ω3 could reduce abnormal morphology and DNA damage while increasing total and progressive motility, characteristics motility, viability, and plasma membrane functional impairment compared with HS-exposed groups. Antioxidant status levels in testicular tissue were improved after administration of ω6 and ω3. Furthermore, after receiving ω6 and ω3, there were significantly lower expression levels of P53 and Caspase-3 and significantly higher expression levels of Bcl-2 compared to the HS-exposed group. Furthermore, the results showed that administration of ω6 and ω3 to rats exposed to HS could increase their in vivo fertility indexes compared to the group not exposed to HS. According to our data, all doses of ω6 and ω3 (particularly doses of ω6-1.25 and ω3-300) can improve the testicular damage, testicular antioxidant defense mechanism, regulate germ cell apoptosis, and increase in vivo fertility indexes.

Whole-genome resequencing of Chinese indigenous sheep provides insight into the genetic basis underlying climate adaptation

BACKGROUND

Chinese indigenous sheep are valuable resources with unique features and characteristics. They are distributed across regions with different climates in mainland China; however, few reports have analyzed the environmental adaptability of sheep based on their genome. We examined the variants and signatures of selection involved in adaptation to extreme humidity, altitude, and temperature conditions in 173 sheep genomes from 41 phenotypically and geographically representative Chinese indigenous sheep breeds to characterize the genetic basis underlying environmental adaptation in these populations.

RESULTS

Based on the analysis of population structure, we inferred that Chinese indigenous sheep are divided into four groups: Kazakh (KAZ), Mongolian (MON), Tibetan (TIB), and Yunnan (YUN). We also detected a set of candidate genes that are relevant to adaptation to extreme environmental conditions, such as drought-prone regions (TBXT, TG, and HOXA1), high-altitude regions (DYSF, EPAS1, JAZF1, PDGFD, and NF1) and warm-temperature regions (TSHR, ABCD4, and TEX11). Among all these candidate genes, eight ABCD4, CNTN4, DOCK10, LOC105608545, LOC121816479, SEM3A, SVIL, and TSHR overlap between extreme environmental conditions. The TSHR gene shows a strong signature for positive selection in the warm-temperature group and harbors a single nucleotide polymorphism (SNP) missense mutation located between positions 90,600,001 and 90,650,001 on chromosome 7, which leads to a change in the protein structure of TSHR and influences its stability.

CONCLUSIONS

Analysis of the signatures of selection uncovered genes that are likely related to environmental adaptation and a SNP missense mutation in the TSHR gene that affects the protein structure and stability. It also provides information on the evolution of the phylogeographic structure of Chinese indigenous sheep populations. These results provide important genetic resources for future breeding studies and new perspectives on how animals can adapt to climate change.

Developmental programming of reproduction in the female animal

Successful reproduction is a cornerstone in food animal industry in order to sustain food production for human. Therefore, various methods focusing on genetics and postnatal environment have been identified and applied to improve fertility in livestock. Yet there is evidence indicating that environmental factors during prenatal and/or neonatal life can also impact the function of reproductive system and fertility in the animals during adulthood, which is called the developmental programming of reproduction. The current review summarizes data associated with the developmental origins of reproduction in the female animals. In this regard, this review focuses on the effect of plane of nutrition, maternal body condition, hypoxia, litter size, maternal age, parity, level of milk production and milk components, lactocrine signaling, stress, thermal stress, exposure to androgens, endocrine disrupting chemicals, mycotoxins and pollutants, affliction with infection and inflammation, and maternal gut microbiota during prenatal and neonatal periods on the neuroendocrine system, puberty, health of reproductive organs and fertility in the female offspring. It is noteworthy that these prenatal and neonatal factors do not always exert their effects on the reproductive performance of the female by compromising the development of organs directly related to reproductive function such as hypothalamus, pituitary, ovary, oviduct and uterus. Since they can impair the development of non-reproductive organs and systems modulating reproductive function as well (e.g., metabolic system and level of milk yield in dairy animals). Furthermore, when these factors affect the epigenetics of the offspring, their adverse effects will not be limited to one generation and can transfer transgenerationally. Hence, pinpointing the factors influencing developmental programming of reproduction and considering them in management of livestock operations could be a potential strategy to help improve fertility in food animals.

The mex-3 3' untranslated region is essential for reproduction during temperature stress

Organisms must sense temperature and modify their physiology to ensure survival during environmental stress. Elevated temperature leads to reduced fertility in most sexually reproducing organisms. Maternally supplied mRNAs are required for embryogenesis. They encode proteins that govern early events in embryonic patterning. RNA-binding proteins (RBPs) are major effectors of maternal mRNA regulation. MEX-3 is a conserved RBP essential for anterior patterning of Caenorhabditis elegans embryos. We previously demonstrated that the mex-3 3' untranslated region (3'UTR) represses MEX-3 abundance in the germline yet is dispensable for fertility. Here, we show that the 3'UTR becomes essential during thermal stress. Deletion of the 3'UTR causes a highly penetrant temperature sensitive embryonic lethality phenotype distinct from a mex-3 null. Loss of the 3'UTR decreases MEX-3 abundance specifically in maturing oocytes and early embryos experiencing temperature stress, suggesting a mechanism that regulates MEX-3 abundance at the oocyte-to-embryo transition is sensitive to temperature. We propose that a primary role of the mex-3 3'UTR is to buffer MEX-3 expression to ensure viability during fluctuating temperature. We hypothesize that a major role of maternally supplied mRNAs is to ensure robust expression of key cell fate determinants in uncertain conditions.

Use of thermography in the long-term evaluation of scrotal surface temperature and its impact on seminal quality in stallions

Scrotal surface thermography is a non-invasive method for assessing testicular thermoregulation in stallions; however, few studies have explored the application of this technique concerning the thermal physiology of equine reproductive systems. This study aimed to evaluate the consistency of testicular thermoregulation in stallions over a year using thermography to measure the scrotal surface temperature (SST). Moreover, we assessed the best region for measuring the surface body temperature compared with the SST. Ten light-breed stallions were used in the experiment. Thermographic images of the scrotal and body surfaces (neck and abdomen) were captured. Fresh, cooled and frozen-thawed semen samples were evaluated to verify the impact of thermoregulation on semen quality. Testicular thermoregulation was maintained throughout the year in stallions amidst changes in the external temperature, as evidenced by the weak correlation between the SST and ambient temperature. A lower correlation was observed between the environmental temperature and body surface temperature (BTS) obtained from the abdomen (BTS-A; R = .4772; p < .0001) than with that obtained from the neck (BTS-N; R = .7259; p < .0001). Moreover, both BTS-A and SST were simultaneously captured in a single image. The consistent quality of the fresh, cooled and frozen semen suggests efficient thermoregulation in stallions throughout the year.

Heatwaves are detrimental to fertility in the viviparous tsetse fly

Heatwaves are increasing in frequency and intensity due to climate change, pushing animals beyond physiological limits. While most studies focus on survival limits, sublethal effects on fertility tend to occur below lethal thresholds, and consequently can be as important for population viability. Typically, male fertility is more heat-sensitive than female fertility, yet direct comparisons are limited. Here, we measured the effect of experimental heatwaves on tsetse flies, Glossina pallidipes, disease vectors and unusual live-bearing insects of sub-Saharan Africa. We exposed males or females to a 3-day heatwave peaking at 36, 38 or 40°C for 2 h, and a 25°C control, monitoring mortality and reproduction over six weeks. For a heatwave peaking at 40°C, mortality was 100%, while a 38°C peak resulted in only 8% acute mortality. Females exposed to the 38°C heatwave experienced a one-week delay in producing offspring, whereas no such delay occurred in males. Over six weeks, heatwaves resulted in equivalent fertility loss in both sexes. Combined with mortality, this lead to a 10% population decline over six weeks compared to the control. Furthermore, parental heatwave exposure gave rise to a female-biased offspring sex ratio. Ultimately, thermal limits of both survival and fertility should be considered when assessing climate change vulnerability.

Effect of heat exposure on prostaglandin production and expression of COX-2, PGES, PGFS, ITGAV and LGALS15 mRNAs in endometrial epithelial cells of buffalo (Bubalus bubalis)

BACKGROUND

Early embryonic mortality is one of the major intriguing factors of reproductive failure that causes considerable challenge to the mammalian cell biologists. Heat stress is the major factor responsible for reduced fertility in farm animals. The present study aimed to investigate the influence of heat stress on prostaglandin production and the expression of key genes, including COX-2, PGES, PGFS, ITGAV and LGALS15, in buffalo endometrial epithelial cells.

METHODS AND RESULTS

Buffalo genitalia containing ovaries with corpus luteum (CL) were collected immediately post-slaughter. The stages of the estrous cycle were determined based on macroscopic observations of the ovaries. Uterine lumens of the mid-luteal phase (days 6-10 of the estrous cycle) were washed and treated with trypsin to isolate epithelial cells, which were then cultured at control temperature (38.5 °C for 24 h) or exposed to elevated temperatures [38.5 °C for 6 h, 40.5 °C for 18 h; Heat Stressed (HS)]. The supernatant and endometrial epithelial cells were collected at various time points (0, 3, 6, 12, and 24 h) from both the control and treatment groups. Although heat stress (40.5 °C) significantly (P < 0.05) increased COX-2, PGES, and PGFS transcripts in epithelial cells but it did not affect the in vitro production of PGF2α and PGE2. The expression of ITGAV and LGALS15 mRNAs in endometrial epithelial cells remained unaltered under elevated temperature conditions.

CONCLUSION

It can be concluded that elevated temperature did not directly modulate prostaglandin production but, it promoted the expression of COX-2, PGES and PGFS mRNA in buffalo endometrial epithelial cells.

Shrinking Alpine chamois: higher spring temperatures over the last 27 years in Switzerland are linked to a 3 kg reduction in body mass of yearlings

Although climate change is considered to be partly responsible for the size change observed in numerous species, the relevance of this hypothesis for ungulates remains debated. We used body mass measurements of 5635 yearlings (i.e. 1.5 years old) of Alpine chamois (Rupicapra rupicapra) harvested in September in the Swiss Alps (Ticino canton) from 1992 to 2018. In our study area, during this period, yearlings shrank by ca 3 kg while temperatures between May and July rose by 1.7°C. We identified that warmer temperatures during birth and the early suckling period (9 May to 2 July in the year of birth) had the strongest impact on yearling mass. Further analyses of year-detrended mass and temperature data indicate that this result was not simply due to changes in both variables over years, but that increases in temperature during this particularly sensitive time window for development and growth are responsible for the decrease in body mass of yearling chamois. Altogether, our results suggest that rising temperatures in the Alpine regions could significantly affect the ecology and evolution of this wild ungulate.

Effects of parity, seasonal heat stress, and colostrum collection time postpartum on colostrum quality of Holstein cattle in an arid region

The aim of this study was to determine effects of parity (primiparous vs. multiparous), seasonal heat stress at calving (summer vs. winter), and time postpartum on some parameters associated with colostrum quality in Holstein cows reared in the Sonoran Desert ecosystem. Forty-seven cows (11 primiparous and 36 multiparous) expected to calve during summer, and 46 cows during winter (14 primiparous and 32 multiparous) were randomly selected. Management and feeding before and after parturition were similar for cows in both seasons. After parturition, colostrum from all cows was evaluated for volume, weight, temperature, density, and content of fat, protein, solids non-fat (SNF), and immunoglobulins (IGG). Data were analyzed with a model that included effects of parity status, calving season, and time postpartum, as well as all interactions. Colostrum produced in summer was warmer (P < 0.01) by almost 6 °C than winter colostrum, while colostrum from multiparous was warmer (P = 0.02) by 1.2 °C than that produced by primiparous cows. Colostrum volume and weight were not impacted by parity, calving season or time postpartum. Density, protein, and SNF content in colostrum were higher (P < 0.01) in multiparous vs. primiparous cows, as well as at parturition (0 h postpartum) than at 12 h postpartum (P < 0.01). At calving (0 h), spring colostrum had higher fat content (P < 0.01) and lower (P < 0.01) IGG concentration than that collected in summer, and no difference (P > 0.05) between seasons was observed for these components at 12 h postpartum. Multiparous cows produced colostrum with higher (P < 0.01) IGG concentrations than primiparous cows. In conclusion, only 0-h colostrum and that from multiparous cows was categorized as "Excellent," meanwhile the colostrum produced under summer heat stress was characterized as "Good" with reduced fat content. While the lacteal secretion collected at 12 post-partum still classified as colostrum, substantially lower contents of IGG, protein, fat, and SNF decreased its classification to "Poor" from the classification of "Excellent" at 0 h postpartum.

MAPKs signaling is obligatory for male reproductive function in a development-specific manner

Mitogen-activated protein kinases (MAPKs) represent widely expressed and evolutionarily conserved proteins crucial for governing signaling pathways and playing essential roles in mammalian male reproductive processes. These proteins facilitate the transmission of signals through phosphorylation cascades, regulating diverse intracellular functions encompassing germ cell development in testis, physiological maturation of spermatozoa within the epididymis, and motility regulation at ejaculation in the female reproductive tract. The conservation of these mechanisms appears prevalent across species, including humans, mice, and, to a limited extent, livestock species such as bovines. In Sertoli cells (SCs), MAPK signaling not only regulates the proliferation of immature SCs but also determines the appropriate number of SCs in the testes at puberty, thereby maintaining male fertility by ensuring the capacity for sperm cell production. In germ cells, MAPKs play a crucial role in dynamically regulating testicular cell-cell junctions, supporting germ cell proliferation and differentiation. Throughout spermatogenesis, MAPK signaling ensures the appropriate Sertoli-to-germ cell ratio by regulating apoptosis, controlling the metabolism of developing germ cells, and facilitating the maturation of spermatozoa within the cauda epididymis. During ejaculation in the female reproductive tract, MAPKs regulate two pivotal events-capacitation and the acrosome reaction essential for maintaining the fertility potential of sperm cells. Any disruptions in MAPK pathway signaling possibly may disturb the testicular microenvironment homeostasis, sperm physiology in the male body before ejaculation and in the female reproductive tract during fertilization, ultimately compromising male fertility. Despite decades of research, the physiological function of MAPK pathways in male reproductive health remains inadequately understood. The current review attempts to combine recent findings to elucidate the impact of MAPK signaling on male fertility and proposes future directions to enhance our understanding of male reproductive functions.

Effect of pre-treatment of melatonin on superovulation response, circulatory hormones, and miRNAs in goats during environmental heat stress conditions

Environmental heat stress has a deleterious impact on farm animal reproductive performance. The purpose of this study was to see how the addition of melatonin affected the efficacy of the superovulation regimen in goats in hot climatic conditions. Sixteen Shiba goats were synchronized and divided into two equal groups (n = 8, each): the melatonin group, which received a single S/C dose of melatonin, and a control group, treated with one ml of corn oil only. Ultrasonographic assessment of ovarian structures (Graafian follicles; GFs and corpus lutea; CLs) morphometry and hemodynamics were performed during the estrous phase of the superovulation (D0) and at day7 after ovulation (D7) of the superovulation regimen. The peripheral reproductive hormones were measured, and microRNAs were characterized. The mean diameter and the total-colored area of GFs during the D0 were significantly (P˂0.05) higher in the melatonin group (5.42 ± 0.11 mm and 1592.20 ± 45.26 pixels, respectively) compared to the control group (4.62 ± 0.12 mm and 1052.55 ± 29.47 pixels, respectively). Concentrations of LH and E2 increased significantly (P˂0.05) in the melatonin group (1.06 ± 0.06 ng/ml and 46.34 ± 2.77 pg/ml, respectively) compared to the control group (0.75 ± 0.12 ng/ml and 29.33 ± 1.89 pg/ml, respectively). At D7, the melatonin-received goats attained greater values in the mean count (6.75 ± 0.33, P˂0.005), diameters (6.08 ± 0.12 mm, P˂0.01), and total-colored area (17137.30 ± 128.53 pixels, P˂0.01) of detected CLs and progesterone concentrations (4.08 ± 0.24 ng/ml) compared to control goats (4.00 ± 0.28, 4.50 ± 0.19 mm, 11156.87 ± 117.90 pixels, and 2.90 ± 0.18 ng/ml respectively). MiRNA expression analysis was identified during both stages denoting several up and downregulated miRNA candidates among the studied groups. In conclusion, incorporating melatonin enhanced the efficiency of the superovulation regimen in goats under hot climatic conditions.

Proteomics Analysis of Pregnancy in Ewes under Heat Stress Conditions and Melatonin Administration

Melatonin is an indoleamine with broad spectrum properties that acts as a regulator of antioxidant and immune response in organisms. In our previous studies, melatonin improved redox status and inflammatory response in pregnant ewes under heat stress conditions. In the present study, using proteomics, the proteins regulated by melatonin during different stages of pregnancy and lambing were assessed. Twenty-two ewes equally divided into two groups, the melatonin (M) (n = 11) and control (C) group (n = 11), participated in the study and were exposed to heat stress during the first months of pregnancy. In the M group, melatonin implants were administered throughout pregnancy, every 40 days, until parturition (a total of four implants per ewe). Blood samples were collected at the beginning of the study simultaneously with the administration of the first melatonin implant (blood samples M1, C1), mating (M2, C2), second implant (M3, C3), fourth implant (M4, C4) and parturition (M5, C5), and MALDI-TOF analysis was performed. The results revealed the existence of 42 extra proteins in samples M2, M3 and M4 and 53 in M5 (sample at parturition) that are linked to melatonin. The biological processes of these proteins refer to boosted immune response, the alleviation of oxidative and endoplasmic reticulum stress, energy metabolism, the protection of the maternal organism and embryo development. This proteomics analysis indicates that melatonin regulates protective mechanisms and controls cell proliferation under exogenous or endogenous stressful stimuli during pregnancy and parturition.

Postweaning Social Isolation Alters Puberty Onset by Suppressing Electrical Activity of Arcuate Kisspeptin Neurons

INTRODUCTION

Postweaning social isolation (PWSI) in rodents is an advanced psychosocial stress model in early life. Some psychosocial stress, such as restrain and isolation, disrupts reproductive physiology in young and adult periods. Mechanisms of early-life stress effects on central regulation of reproduction need to be elucidated. We have investigated the effects of PWSI on function of arcuate kisspeptin (ARCKISS1) neurons by using electrophysiological techniques combining with monitoring of puberty onset and estrous cycle in male and female Kiss1-Cre mice.

METHODS

Female mice were monitored for puberty onset with vaginal opening examination during social isolation. After isolation, the estrous cycle of female mice was monitored with vaginal cytology. Anxiety-like behavior of mice was determined by an elevated plus maze test. Effects of PWSI on electrophysiology of ARCKISS1 neurons were investigated by the patch clamp method after intracranial injection of AAV-GFP virus into arcuate nucleus of Kiss1-Cre mice after the isolation period.

RESULTS

We found that both male and female isolated mice showed anxiety-like behavior. PWSI caused delay in vaginal opening and extension in estrous cycle length. Spontaneous-firing rates of ARCKISS1 neurons were significantly lower in the isolated male and female mice. The peak amplitude of inhibitory postsynaptic currents to ARCKISS1 neurons was higher in the isolated mice, while frequency of excitatory postsynaptic currents was higher in group-housed mice.

CONCLUSION

These findings demonstrate that PWSI alters pre- and postpubertal reproductive physiology through metabolic and electrophysiological pathways.

Monitoring of taurine dietary supplementation effect on parameters of Duroc boar ejaculate in summer season

The aim of this experiment was to find out whether the taurine supplementation in daily ration had an effect on quantity or quality of Duroc boar ejaculate. The experiment duration was from June to August, when it could assumed the possible occurrence of heat stress. For the study was chosen 12 Duroc boars of approximately the same age and condition. The control group of 6 Duroc boars was fed only by basic diet and the experimental group of 6 Duroc boars was fed by the same basic diet with supplementation of 15 g taurine/boar/day. Ejaculate was collected once a week by hand glowed technique. From ejaculate parameters were monitored volume of ejaculate, sperm concentration, total amount of sperm, morphologically abnormal sperm, taurine concentration and GSH/GSSH concentration. From microscopic analysis, results were statistically significant in motility in June and July (P<0.05). In biochemical results, a significant difference (P<0.05) has been found between the experimental groups in the concentrations of taurine as well as GSH/GSSG in ejaculate which indicates the effect of heat stress on boars during the experimental period.

Breaking the fast: first report of dives and ingestion events in molting southern elephant seals

Southern elephant seals (SES) experience a 'catastrophic molt', a costly event characterized by the renewal of both hair and epidermis that requires high peripheral vascular circulation. Molting animals are therefore constrained by high metabolic heat loss and are thought to fast and remain on land. To examine the ability of individuals to balance the energetic constraints of molting on land we investigate the stomach temperature and movement patterns of molting female SES. We find that 79% of females swam and 61% ingested water or prey items, despite the cost of cold-water exposure while molting. This behavior was related to periods of warm and low wind conditions, and females that dived and ingested more often, lost less body mass. We conclude that the paradigm of fasting during the molt in this species, and the fitness consequences of this behavior should be reconsidered, especially in the context of a changing climate.

High Temperature-Induced m6A Epigenetic Changes Affect Early Porcine Embryonic Developmental Competence in Pigs

N6-methyladenosine (m6A), the most prevalent modification in eukaryotic messenger RNA (mRNA), plays a key role in various developmental processes in mammals. Three proteins that affect RNA m6A modification have been identified: methyltransferases, demethylases, and m6A-binding proteins, known as "writer," "eraser," and "reader" proteins, respectively. However, changes in the m6A modification when early porcine embryos are exposed to stress remain unclear. In this study, we exposed porcine oocytes to a high temperature (HT, 41°C) for 10 h, after which the mature oocytes were parthenogenetically activated and cultured for 7 days to the blastocyst stage. HT significantly decreased the rates of the first polar body extrusion and blastocyst formation. Further detection of m6A modification found that HT can lead to increased expression levels of "reader," YTHDF2, and "writer," METTL3, and decreased expression levels of "eraser," FTO, resulting in an increased level of m6A modification in the embryos. Additionally, heat shock protein 70 (HSP70) is upregulated under HT conditions. Our study demonstrated that HT exposure alters m6A modification levels, which further affects early porcine embryonic development.

Developmental programming of production and reproduction in dairy cows: II. Association of gestational stage of maternal exposure to heat stress with offspring's birth weight, milk yield, reproductive performance and AMH concentration during the first lactation period

Although the negative effect of maternal exposure to heat stress on production and reproduction of offspring has been reported, there are some discrepancies among various studies about which gestational stage is more critical in this regard. Therefore, the present research was conducted to identify during which stage(s) of pregnancy maternal exposure to heat stress would lead to more dramatic decrease in productive and reproductive performance of offspring. To this end, offspring were classified based on the gestational stage they were in utero exposed to heat stress into four categories, including heat stress exposure (HSE) during only the first trimester of gestation (HSE1), HSE during the first and second trimester of gestation (HSE2), HSE during the second and third trimester of gestation (HSE3) and HSE during only the third trimester of gestation (HSE4). In study I, data of birth weight, milk yield and reproductive variables of 11,788 offspring and data of the month they were conceived were retrieved. In study II, blood samples (n = 521) were collected from offspring in various categories of HSE for measurement of serum AMH. Offspring in HSE1 and HSE2 categories were heavier than offspring in HSE3 and HSE4 categories (P < 0.0001). Offspring in HSE1 and HSE3 categories had the lowest and highest milk production, respectively (P < 0.05). First service conception rate was the greatest and worst in HSE1 and HSE4 categories, respectively (P < 0.05). Service per conception and calving to conception interval were greater in HSE2 than HSE4 category (P < 0.05). Concentration of AMH was lower in HSE1 than HSE4 category (P < 0.05). In conclusion, the present study indicated that the early stage of gestation could be a more critical period for the negative impact of in utero heat stress on developmental programming of milk production and ovarian reserves. Yet an evident temporal pattern for the adverse effect of maternal heat stress on developmental programming of reproductive performance in offspring was not found.

The detrimental impact of high environmental temperature on physiological response, growth, milk production, and reproductive efficiency of ruminants

The optimal environments for ruminants are air temperatures between 13 and 20 °C, winds between 5 and 18 km/h, humidity levels between 55 and 65%, and a moderate amount of sunlight. In tropical and subtropical regions, climate is the top factor restricting animal growth and reproductive efficiency. The digestive system, blood biochemical components, and hormones all go through a range of physiological changes at high temperatures. Ruminant animals respond to heat stress by drinking more water, breathing more quickly, panting, and raising their rectal temperatures while reducing their activity levels, intake of roughage, and rumination. Blood metabolites and biochemical modifications are negatively impacted by the concentration of blood biochemical components and hormonal levels, particularly those of anabolic hormones, which are decreased as a result of the animals' exposure to high environmental temperatures. Changes in blood metabolite and hormone levels were influenced by the duration of exposure to high temperatures, the level of background heat, and the species, breed, and age of the animals. The major biological changes caused by heat stress have a negative impact on growth, milk production, and reproduction. Animals subjected to high environmental temperatures also undergo reductions in feed intake and feed efficiency. These changes eventually impair ruminant reproduction and production abilities.

Molecular, enzymatic responses and in vitro embryonic developmental competency of heat-shocked buffalo embryos co-cultured with granulosa cells monolayer

The present study was designed to establish a suitable alternative approach to mitigate the adverse effect of high culture temperature on in vitro embryo development and the related molecular response in buffalo. Pre-cultured granulosa cells (GCs) were used as a monolayer during in vitro embryo culture until day 8 (day of fertilization = D0). Post fertilization, presumptive embryos were randomly assigned into two culture conditions: embryos cultured in the presence of GCs monolayer under normal culture temperature (N: 38.5 °C; GEN group) or heat shock (H: 40.5 °C; GEH group) and their counterpart groups of embryos cultured without GCs (EN and EH groups). Additionally, two groups of GCs monolayer were cultured without embryos up to day 8 under 38.5 °C (GN) or 40.5 °C (GH) for further spent culture media enzymatic analyses. Heat shock was administered for the first 2 h of culture then continued at 38.5 °C until day 8. The results indicated that under heat treatment, GCs enhanced (P ≤ 0.05) embryo cleavage and development (day 8) rates, which were comparable to the embryos cultured at 38.5 °C. On the molecular level, blastocysts of the GEH group showed similar expressions of metabolism-regulating genes (CPT2 and SlC2A1/GLUT1) and an antioxidant gene (SOD2) when compared to the blastocysts of the EN group. The relative expression of HSP90 was significantly up-regulated under heat shock and/or co-culture conditions. However, HSF1 expression was increased (P ≤ 0.05) in the GEH group. No statistical differences were observed among the study groups for the pluripotency gene NANOG, and stress resistance transcript NFE2L2. Regarding the enzymatic profile, the concentrations of SOD, total protein, and MDA were decreased (P ≤ 0.05) in the GEH group compared to the cultured GCs without embryos (GH group). In conclusion, GCs as a monolayer have a beneficial impact on alleviating heat stress at the zygote stage through the regulatory mechanisms of metabolic activity, defense system, and heat shock response genes.

Bovine oviductal organoids: a multi-omics approach to capture the cellular and extracellular molecular response of the oviduct to heat stress

BACKGROUND

The mammalian oviduct is a complex, fibromuscular organ known for its role in orchestrating a series of timely and dynamic changes to suitably support early embryogenesis. Climate change-induced heat stress (HS) is one of the largest single stressors compromising reproductive function in humans and farm animals via systemic changes in the redox status of the maternal environment, adversely affecting fertilization and early embryonic development. Oviductal organoids represent a unique 3-dimensional, biomimetic model to study the physiology of the oviduct and its subsequent impact on embryo development under various environmental conditions.

RESULTS

Our study is the first to demonstrate an innovative approach to understanding the cascade of molecular changes sustained by bovine oviductal organoids under HS and the subsequent maternal signals harnessed within their secreted extracellular vesicles (EVs). Transcriptomic analysis of oviductal organoids exposed to HS revealed 2,570 differentially expressed genes (1,222 up- and 1,348 downregulated), while EV-coupled miRNome analysis disclosed 18 miRNAs with significant differential expression (12 up- and 6 downregulated) in EVs from thermally stressed organoids compared to EVs released from organoids cultured under thermoneutral conditions. Genes activated in oviductal organoids in response to thermal stress, include: COX1, ACTB, CST6, TPT1, and HSPB1, while miR-1246, miR-148a, miR21-5p, miR-451, and miR-92a represent the top highly abundant EV-coupled miRNAs released in response to HS. Pathway analysis of genes enriched in organoids exposed to thermal stress showed the enrichment of endocrine resistance, cellular senescence, and notch signaling pathways. Similarly, EV-coupled miRNAs released from thermally stressed organoids showed their potential regulation of genes involved in cellular senescence, p53 signaling, and TGF-beta signaling pathways.

CONCLUSIONS

In conclusion, the cellular and extracellular response of bovine oviductal organoids to in vitro HS conditions reveal the prospective impact of environmental HS on the physiology of the oviduct and the probable subsequent impacts on oocyte fertilization and early embryo development. Future studies elucidating the potential impact of HS-associated EVs from oviductal organoids on oocyte fertilization and preimplantation embryo development, would justify the use of an organoid model to optimally understand the oviduct-embryo communication under suboptimal environments.

5-Aminolevulinic acid/sodium ferrous citrate improves the quality of heat-stressed bovine oocytes by reducing oxidative stress

A high temperature-humidity index during summer has deleterious effects on mitochondrial function, reducing oocyte developmental competence. 5-Aminolevulinic acid (5-ALA) and sodium ferrous citrate (SFC) are both known to support mitochondrial function and have strong anti-oxidant and anti-apoptotic activities. This study aimed to determine the mechanism of action of 5-ALA/SFC on oocyte quality. Bovine oocytes were collected from medium-sized follicles during summer (July-September, temperature-humidity index:76.6), cultured with 0, 1, 2, 4, and 8 µM 5-ALA with SFC at a molar ratio of 1:0.125, fertilized, and cultured for 10 days. The addition of 8/1 µM 5-ALA/SFC had a deleterious effect on oocyte cleavage rate in comparison with control oocytes, but did not affect the blastocyst rate, while 1/0.125 µM 5-ALA/SFC had a significantly higher increase in blastocyst rate than 8/1 µM 5-ALA/SFC. The addition of 1/0.125 and 2/0.25 µM 5-ALA/SFC improved oocyte quality by increasing the mitochondrial distribution pattern and metaphase-II oocytes, reducing reactive oxygen species and upregulating nuclear factor erythroid-2-related factor 2, heme oxygenase-1, and superoxide dismutase-1 in oocytes, and nuclear factor erythroid-2-related factor 2 and mitochondrial transcription factor A in cumulus cells. These results indicate that 1/0.125 and 2/0.25 µM 5-ALA/SFC may support oocyte quality and developmental competence and provide anti-oxidant actions in cumulus-oocyte complexes.

The effect of short-term exposure to high temperatures on male courtship behaviour and mating success in the fruit fly Drosophila virilis

Human-induced climate change is leading to higher average global temperatures and increasingly extreme weather events. High temperatures can have obvious effects on animal survival, particularly in ectotherms. However, the temperature at which organisms become sterile may be significantly lower than the temperature at which other biological functions are impaired. In the fruit fly Drosophila virilis, males are sterilized at temperatures above 34 °C, but are still active and able to mate normally. We investigated the male behavioural changes associated with high-temperature fertility loss. We exposed males to a warming treatment of 34.4 °C or 36.6 °C for 4 h, and then recorded their mating behaviour after being allowed to recover for 24 h. Previous work in this species suggests that males exposed to 34.4 °C lose the ability to produce new sperm, but can utilize mature sperm produced before the heat shock. We therefore predicted that these males would increases their courtship rate, and reduce their choosiness, in order to try to ensure a mating before their remaining mature sperm die. In contrast, over two-thirds of males exposed to 36.6 °C are completely sterile. In standard mating trials, earlier exposure to 34.4 °C or 36.6 °C did not affect male courtship behaviour when compared to control males kept at 23 °C. Exposure to high temperatures also did not alter the extent to which males directed courtship toward females of the same species. However, males exposed to 36.6 °C were significantly slower to mate, and had a reduced likelihood of mating, when compared to control males. Overall, exposure to high temperatures did not alter male courtship behaviour, but did lower their likelihood of mating. This suggests that females can distinguish between normal and heat-sterilized males before mating, and that female mate choice may at least partly mitigate the population-level consequences of high-temperature induced male sterility in this species.

Ambient temperature, heat stress and fetal growth: A review of placenta-mediated mechanisms

Pregnancy is increasingly considered a period of vulnerability for extreme heat exposure. Multiple lines of evidence support that heat stress is associated with placental insufficiency, poor fetal growth and decreased birth weight. In this narrative review, we first summarize evidence linking ambient temperature or experimentally-induced heat stress with fetal and placental growth outcomes in humans, ruminants and murine species. We then synthesize the literature on putative underlying biological pathways with a focus on the placenta. Reviewed mechanisms include: reduced uterine-placental blood flow, impaired supply of metabolic substrates to the fetus, activation of the maternal stress-response system, and disruption of other endocrine and immune system endpoints. Taken together, this body of evidence supports that exposure to extreme ambient heat likely has adverse consequences for placental development and function. However, research investigating placenta-mediated pathophysiological mechanisms in humans remains extremely limited.

Kidney function impairment in men with primary infertility: A case-control analysis

BACKGROUND

Infertile men have a worse overall health status than their fertile counterparts.

OBJECTIVE

We aimed to (1) compare kidney function in men presenting for primary couple's infertility with that of fertile men and (2) assess kidney function impairment toward sperm quality in infertile men.

MATERIALS AND METHODS

In this case-control study, 387 consecutive white-European infertile men were matched by age with 134 same-ethnicity fertile men. Complete clinical and laboratory data were available for each patient. The Chronic Kidney Disease Epidemiology Collaboration function was used for estimated glomerular filtration rate calculation. Kidney functional impairment was defined as an estimated glomerular filtration rate <90 mL/min per 1.73 m2 , according to the Kidney Disease Improving Global Outcomes criteria. Multivariable logistic regression analysis was used to (1) assess the association between kidney function impairment and infertility status and (2) investigate the association between kidney function and semen analysis abnormalities in infertile men.

RESULTS

After matching, 34 (8.8%) infertile men depicted at least a mild unknown impairment of kidney function compared to only four (3%) fertile men, with four (3%) of the infertile presenting with an overt kidney function impairment (estimated glomerular filtration rate <60 mL/min per 1.73 m2 ). There were no differences in terms of age, body mass index and rate of comorbidities between the two groups (all p > 0.05). After adjusting for major confounders, infertility status was associated with a higher risk of reduced estimated glomerular filtration rate (odds ratio 3.20; 95% confidence interval 1.21-5.2; p = 0.002). Conversely, estimated glomerular filtration rate was not associated with sperm abnormalities in infertile men.

CONCLUSIONS

Mild kidney function impairment was found in 9% of asymptomatic and unaware men presenting for primary couple's infertility investigation. This novel finding corroborates growing data on a significant association of male infertility with a poorer overall male health status and the need for tailored preventive strategies.

Identification of temporal patterns of environmental heat stress of Holstein dairy heifers raised in Mediterranean climate during their in-utero and post-natal life periods and modelling their effects on age at first calving

A retrospective study was conducted to evaluate temporal patterns of environmental heat stress during the in-uterus period of development (IUP) and the 3-month post-natal (PN) period of dairy heifers, and to estimate their association with the age at first calving (AFC). Data from 30 dairy herds in Northern Greece including 9098 heifers were extracted from National Cattle Database. Data (2005-2019) regarding 230,100 farm-specific ambient daily temperature and relative humidity records, were obtained from ERA5-Land. Average monthly Temperature-Humidity-Index values (THI; low≤68, and high>68) were calculated and matched for each heifer to their IUP and PN. Subsequently, Cluster Analysis was used with monthly THIs as predictors to allocate heifers to THI clusters. The association of clusters with AFC was assessed with Generalized Linear Mixed Model analysis, an extended form of multiple linear regression. Finally, 8 Heat Stress Clusters (HSC; namely HSC-1 to HSC-8) were identified. Compared to HSC-8 (8th-9th IUP months and 1st PN month) heifers of HSC-5 (4th-7th IUP months) and HSC-6 (6th-8th IUP months) calved 13.8 and 17.8 days later, respectively (P < 0.01-0.001). Moreover, when AFC was treated as a binary variable, heifers of HSC-5 and HSC-6 had 1.15 and 1.34 (P < 0.01-0.001) higher risk of calving for the first time later than 787 days compared to HSC-8, respectively.

Protective effects of epigallocatechin gallate in the mice induced by chronic scrotal hyperthermia

One of the most common complications of chronic scrotal hyperthermia (SHT) is a serious disorder in the male reproductive system. The most important factor in the occurrence of these disorders is oxidative stress. Currently, we investigated the effects of epigallocatechin gallate (EGCG), as a highly potent antioxidant, against cells and tissue disorders in mice affected by chronic SHT. Fifty-six male adult NMRI mice were allocated into seven equal groups. Except the non-treated (Control) group, six other groups were exposed to heat stress. Two treated groups including Preventive and Curative received oral administration of EGCG (50 mg/kg/day) starting immediately before heat exposure and fifteen consecutive days after the end of the heat exposure, respectively. For each treated group, two subgroups including positive control (Pre/Cur + PC groups) and vehicle (Pre/Cur + vehicle groups) were considered. At the end of the study, sperm characteristics, testosterone levels, stereological parameters, apoptosis, oxidant state, and molecular assessments were performed. We found that the sperm parameters, testosterone levels, the numerical density of spermatogonia, primary spermatocytes, spermatids, sertoli, leydig cells, and seminiferous tubules, biochemical factors (except MDA), and expression of c-kit gene were significantly higher in the Preventive and Curative groups, especially in Preventive ones, compared to other groups (P < 0.05). This is while expression of HSP72 and NF-κβ genes, MDA levels, as well as density of apoptotic cells considerably decreased in both EGCG-treated groups compared to other groups and it was more pronounced in Preventive ones (P < 0.05). Generally, EGCG attenuated cellular and molecular disorders induced by heat stress in the testis and it was more pronounced in Preventive status.

Stress Factors and Their Effects on Productivity in Sheep

Products obtained from sheep have an economically important place in the world. Their adaptability to different climatic conditions, their ease of care and feeding, their high utilization of poor pasture areas with low yield and quality, the ease of flock management, their high twinning rate, and their short intergenerational period are some of the advantages of sheep production. Sheep production has the ability to adapt better to environmental stress factors, as can be understood from the presence of sheep in different geographical regions at a global level. However, the changes in environmental conditions and production cause some negative results in animals. All these negative results expose animals to various stress factors (heat, cold, transport, treatment, nutritional, shearing, weaning, etc.). All stress factors that directly and indirectly affect sheep production ultimately lead to compromised performance, decreased productivity, increased mortality, and adverse effects on the immune system. In order to cope with the current stress parameters in animals and to achieve optimum production, a holistic approach is needed according to the environmental conditions and available resources. It is important to consider the factors involved in these responses in order to manage these processes correctly and to develop adequate strategies and improve sheep welfare. This review aimed to reveal the importance of some stress factors in sheep and their effects on sheep productivity.

Allostasis in Neuroendocrine Systems Controlling Reproduction

Allostasis provides a supporting role to the homeostatic control of biological variables in mammalian species. While the concept of homeostasis is related to the control of variables within a set point or range that are essential to life, allostasis refers to systems that facilitate adaptation to challenges that the organism faces and the new requirements for survival. Essential for such adaptation is the role played by the brain in eliciting neural and neuroendocrine responses. Reproductive function is fundamental for the survival of species but is costly in energetic terms and requires a synchrony with an ever-changing environment. Thus, in many species reproductive function is blocked or delayed over immediate challenges. This review will cover the physiological systems and neuroendocrine pathways that supply allostatic control over reproductive neuroendocrine systems. Light, hypoxia, temperature, nutrition, psychosocial, and immune mediators influence the neuroendocrine control of reproductive functions through pathways that are confluent at the paraventricular nucleus; however, understanding of the integrative responses to these stimuli has not been clarified. Likely, the ultimate consequence of these allostatic mechanisms is the modification of kisspeptin and gonadotropin-releasing hormone neuronal activity, thus compromising reproduction function in the short term, while preserving species survivability.

Rapid heat hardening in embryos of the lizard Anolis sagrei

Adaptive thermal tolerance plasticity can dampen the negative effects of warming. However, our knowledge of tolerance plasticity is lacking for embryonic stages that are relatively immobile and may benefit the most from an adaptive plastic response. We tested for heat hardening capacity (a rapid increase in thermal tolerance that manifests in minutes to hours) in embryos of the lizard Anolis sagrei. We compared the survival of a lethal temperature exposure between embryos that either did (hardened) or did not (not hardened) receive a high but non-lethal temperature pre-treatment. We also measured heart rates (HRs) at common garden temperatures before and after heat exposures to assess metabolic consequences. 'Hardened' embryos had significantly greater survival after lethal heat exposure relative to 'not hardened' embryos. That said, heat pre-treatment led to a subsequent increase in embryo HR that did not occur in embryos that did not receive pre-treatment, indicative of an energetic cost of mounting the heat hardening response. Our results are not only consistent with adaptive thermal tolerance plasticity in these embryos (greater heat survival after heat exposure), but also highlight associated costs. Thermal tolerance plasticity may be an important mechanism by which embryos respond to warming that warrants greater consideration.

Heat stress in horses: a literature review

Healthy adult horses can balance accumulation and dissipation of body heat to maintain their body temperature between 37.5 and 38.5 °C, when they are in their thermoneutral zone (5 to 25 °C). However, under some circumstances, such as following strenuous exercise under hot, or hot and humid conditions, the accumulation of body heat exceeds dissipation and horses can suffer from heat stress. Prolonged or severe heat stress can lead to anhidrosis, heat stroke, or brain damage in the horse. To ameliorate the negative effects of high heat load in the body, early detection of heat stress and immediate human intervention is required to reduce the horse's elevated body temperature in a timely manner. Body temperature measurement and deviations from the normal range are used to detect heat stress. Rectal temperature is the most commonly used method to monitor body temperature in horses, but other body temperature monitoring technologies, percutaneous thermal sensing microchips or infrared thermometry, are currently being studied for routine monitoring of the body temperature of horses as a more practical alternative. When heat stress is detected, horses can be cooled down by cool water application, air movement over the horse (e.g., fans), or a combination of these. The early detection of heat stress and the use of the most effective cooling methods is important to improve the welfare of heat stressed horses.

Notch pathway is required for protection against heat stress in spermatogonial stem cells in medaka

Gamete production is a fundamental process for reproduction; however, exposure to stress, such as increased environmental temperature, can decrease or even interrupt this process, affecting fertility. Thus, the survival of spermatogonial stem cells (SSCs) is crucial for the recovery of spermatogenesis upon stressful situations. Here, we show that the Notch pathway is implicated in such survival, by protecting the SSCs against thermal stress. First, we corroborated the impairment of spermatogenesis under heat stress in medaka, observing an arrest in metaphase I at 10 days of heat treatment, an increase in the number of spermatocytes, and downregulation of ndrg1b and sycp3. In addition, at 30 days of treatment, an interruption of spermatogenesis was observed with a strong loss of spermatocytes and spermatids. Then, the exposure of adult males to thermal stress condition induced apoptosis mainly in spermatogenic and supporting somatic cells, with the exception of the germinal region, where SSCs are located. Concomitantly, the Notch pathway-related genes were upregulated, including the ligands (dll4, jag1-2) and receptors (notch1a-3). Moreover, during thermal stress presenilin enhancer-2 (pen-2), the catalytic subunit of γ-secretase complex of the Notch pathway was restricted to the germinal region of the medaka testis, observed in somatic cells surrounding type A spermatogonia (SGa). The importance of Notch pathway was further supported by an ex vivo approach, in which the inhibition of this pathway activity induced a loss of SSCs. Overall, this study supports the importance of Notch pathways for the protection of SSCs under chronic thermal stress.

Influences of Maternal Weight and Geographic Factors on Offspring Traits of the Edible Dormouse in the NE of the Iberian Peninsula

The main goal of this study was to analyze the reproductive patterns of edible dormouse (Glis glis) populations in the northeast of the Iberian Peninsula using an 18-year period of data obtained from nest boxes collected between 2004 and 2021. The average litter size in Catalonia (Spain) was 5.5 ± 1.60 (range: 2-9, n = 131), with litter sizes between 5 and 7 pups as the more frequent. The overall mean weight in pink, grey and open eyes pups was 4.8 g/pup, 11.7 g/pup and 23.6 g/pup, respectively. No differences in offspring weights between sexes were found in any of the three age groups. Maternal body weight was positively associated with mean pup weight, whereas no correlation between the weight of the mothers and litter size was found. The trade-off between offspring number and size was not detected at birth. Regarding litter size variation across the geographic gradient (and their climatic gradient associated) from the southernmost populations of the Iberian Peninsula located in Catalonia to the Pyrenees region in Andorra, no evidence to suggest that geographic variables affect litter size was found, discarding (1) an investment in larger litters to compensate shorter seasons related to higher altitudes or northern latitudes, and (2) variation in litter size related to weather changes (e.g., temperature and precipitation) along latitudinal and/or altitudinal gradients.

Effects of weather and social factors on hormone levels in the European badger (Meles meles)

Animals in the wild continually experience changes in environmental and social conditions, which they respond to with behavioural, physiological and morphological adaptations related to individual phenotypic quality. During unfavourable environmental conditions, reproduction can be traded-off against self-maintenance, mediated through changes in reproductive hormone levels. Using the European badger (Meles meles) as a model species, we examine how testosterone in males and oestrogens in females respond to marked deviations in weather from the long-term mean (rainfall and temperature, where badger earthworm food supply is weather dependent), and to social factors (number of adult males and females per social group and total adults in the population), in relation to age, weight and head-body length. Across seasons, testosterone levels correlated postively with body weight and rainfall variability, whereas oestrone correlated positively with population density, but negatively with temperature variability. Restricting analyses to the mating season (spring), heavier males had higher testosterone levels and longer females had higher oestradiol levels. Spring oestrone levels were lower when temperatures were above normal. That we see these effects for this generally adaptive species with a broad bioclimatic niche serves to highlight that climatic effects (especially with the threat of anthropogenic climate change) on reproductive physiology warrant careful attention in a conservation context.

Granulosa cell-derived extracellular vesicles mitigate the detrimental impact of thermal stress on bovine oocytes and embryos

Climate change-induced global warming results in rises in body temperatures above normal physiological levels (hyperthermia) with negative impacts on reproductive function in dairy and beef animals. Extracellular vesicles (EVs), commonly described as nano-sized, lipid-enclosed complexes, harnessed with a plethora of bioactive cargoes (RNAs, proteins, and lipids), are crucial to regulating processes like folliculogenesis and the initiation of different signaling pathways. The beneficial role of follicular fluid-derived EVs in inducing thermotolerance to oocytes during in vitro maturation (IVM) has been evidenced. Here we aimed to determine the capacity of in vitro cultured granulosa cell-derived EVs (GC-EVs) to modulate bovine oocytes’ thermotolerance to heat stress (HS) during IVM. Moreover, this study tested the hypothesis that EVs released from thermally stressed GCs (S-EVs) shuttle protective messages to provide protection against subsequent HS in bovine oocytes. For this, sub-populations of GC-EVs were generated from GCs subjected to 38.5°C (N-EVs) or 42°C (S-EVs) and supplemented to cumulus-oocyte complexes (COCs) matured in vitro at the normal physiological body temperature of the cow (38.5°C) or HS (41°C) conditions. Results indicate that S-EVs improve the survival of oocytes by reducing ROS accumulation, improving mitochondrial function, and suppressing the expression of stress-associated genes thereby reducing the severity of HS on oocytes. Moreover, our findings indicate a carryover impact from the addition of GC-EVs during oocyte maturation in the development to the blastocyst stage with enhanced viability.

Climate change and pregnancy complications: From hormones to the immune response

Pregnant women are highly vulnerable to adverse environments. Accumulating evidence highlights that increasing temperatures associated with the ongoing climate change pose a threat to successful reproduction. Heat stress caused by an increased ambient temperature can result in adverse pregnancy outcomes, e.g., preterm birth, stillbirth and low fetal weight. The pathomechanisms through which heat stress interferes with pregnancy maintenance still remain vague, but emerging evidence underscores that the endocrine system is severely affected. It is well known that the endocrine system pivotally contributes to the physiological progression of pregnancy. We review – sometimes speculate - how heat stress can offset hormonal dysregulations and subsequently derail other systems which interact with hormones, such as the immune response. This may account for the heat-stress related threat to successful pregnancy progression, fetal development and long-term children’s health.

Ecology and age, but not genetic ancestry, predict fetal loss in a wild baboon hybrid zone

OBJECTIVES

Pregnancy failure represents a major fitness cost for any mammal, particularly those with slow life histories such as primates. Here, we quantified the risk of fetal loss in wild hybrid baboons, including genetic, ecological, and demographic sources of variance. We were particularly interested in testing the hypothesis that hybridization increases fetal loss rates. Such an effect would help explain how baboons may maintain genetic and phenotypic integrity despite interspecific gene flow.

MATERIALS AND METHODS

We analyzed outcomes for 1020 pregnancies observed over 46 years in a natural yellow baboon-anubis baboon hybrid zone. Fetal losses and live births were scored based on records of female reproductive state and the appearance of live neonates. We modeled the probability of fetal loss as a function of a female's genetic ancestry (the proportion of her genome estimated to be descended from anubis [vs. yellow] ancestors), age, number of previous fetal losses, dominance rank, group size, climate, and habitat quality using binomial mixed effects models.

RESULTS

Female genetic ancestry did not predict fetal loss. Instead, the risk of fetal loss is elevated for very young and very old females. Fetal loss is most robustly predicted by ecological factors, including poor habitat quality prior to a home range shift and extreme heat during pregnancy.

DISCUSSION

Our results suggest that gene flow between yellow and anubis baboons is not impeded by an increased risk of fetal loss for hybrid females. Instead, ecological conditions and female age are key determinants of this component of female reproductive success.

Animal welfare and effects of per-female stress on male and cattle reproduction—A review

Thermal stress causes severe effects on the wellbeing and reproduction of cattle, including changes in oogenesis and spermatogenesis, generating great concerns, which last for decades. In cattle, the occurrence of thermal stress is associated with a reduction in the production of spermatozoids and ovarian follicles, in addition to the increase of major and minor defects in gametes or in their intermediate stages. In bovine females able to reproduce, a reduction in the rate of estrus manifestation and an increase in embryonic mortality has been observed. Therefore, keeping animals on good welfare conditions, with water supply and in shaded areas can favor the improvement of different reproductive parameters. For all this, the present study aimed to gather, synthesize and argue recent studies related to animal welfare, focusing on the effects of thermal stress on the reproduction of cattle, aiming to support possible strategies to mitigate the harmful effects of thermal stress in this species.

Effects of heat stress on sperm quality of French Bulldogs

This study aimed to evaluate the effects of heat stress (HS) and its duration on semen quality, serum testosterone, pulsatility and resistibility index of the testicular artery of French Bulldogs. Eight male French Bulldogs, 3-7 years old, 12.63 ± 1.8 Kg were adapted and trained for two months. Room temperature was 21 °C. Semen was collected by digital stimulation. The median of four andrological evaluations was T0. Heat was applied to the scrotum using an electrical heat pad at 40 °C for 11 min. Rectal temperature (RT) and scrotum temperature were evaluated using a mercury thermometer and an infrared thermography camera before and after HS. Semen was evaluated immediately (T1) and after seven (T7), 14 (T14), 21 (T21), 28 (T28) and 60 (T60) days after HS. Semen parameters included macroscopic (volume, color and viscosity) and microscopic (sperm motility and vigor, percentage of morphologically normal or defected spermatozoa, sperm concentration and total number of sperm cells) aspects. A pulsed colored doppler ultrasound was performed on the testicular artery at the spermatic cord and epididymis region before and immediately after HS. Serum testosterone was analyzed before, 48 and 96 h after HS. Data was analyzed by ANOVA using SAS. There was a 1.23 °C increase on RT and a 4.98 °C increase on thermograph after HS. Sperm motility decreased at T1 (P < 0.05) and tended to stay lower at T7 (P = 0.056). It improved at T14, but reduced again at T21 (P < 0.05). At T28 and T60 motility was normal. Vigor was lower at T1 (P < 0.05), normal at T7 and T14, but decreased at T21 (P = 0.054), at T28 and T60 it was not different than T0. Sperm concentration was lower at T1 (P < 0.05) and not different from T0 at other timepoints. Volume color and viscosity were not different. Total sperm per ejaculate was reduced at T1 and T7 (P < 0.05) and tended to be lower at T14 (P = 0.057). T21, T28 and T60 were not different than T0. There was a decrease in normal sperm cells and an increase in defected sperm at T7. There was no difference within T14, T21, T28 and T60. The raise in pathologies at T7 was from an increase in minor defects (P < 0.05). There was no difference in serum concentration of testosterone nor pulsatility and resistivity index before and after HS. In conclusion, induction of HS directly to the testis reduces sperm quality in French Bulldog. This impairment is immediately and transitory.

Validating the female fertility estimated breeding value in Australian commercial dairy herds

We conducted a retrospective cohort study to validate the efficacy of the Australian multitrait fertility estimated breeding value (EBV). We did this by determining its associations with phenotypic measures of reproductive performance (i.e., submission rate, first service conception rate, and early calving). Our secondary aim was to report the associations between these reproductive outcomes and management and climate-related factors hypothesized to affect fertility. Our study population included 38 pasture-based dairy herds from the northern Victorian irrigation region in Australia. We collected records for 86,974 cows with 219,156 lactations and 438,578 mating events from the date on which managers started herd recording until December 2016, comprising both fertility-related data such as insemination records, calving dates, and pregnancy test results, and systems-related data such as production, herd size, and calving pattern. We also collected hourly data from 2004 to 2017 from the closest available weather station to account for climate-related factors (i.e., temperature humidity index; THI). Multilevel Cox proportional hazard models were used to analyze time-to-event outcomes (days to first service, days to cow calving following the planned herd calving start date), and multilevel logistic regression models for binomial outcomes (conception to first service) in the Holstein-Friesian and Jersey breeds. A 1-unit increase in daughter fertility EBV was associated with a 5.4 and 8.2% increase in the daily hazard of calving in the Holstein-Friesian and Jersey breeds respectively. These are relative increases (i.e., a Holstein-Friesian herd with a 60% 6-wk in-calf rate would see an improvement to 63.2% with a 1-unit increase in herd fertility EBV). Similar results were obtained for submission and conception rate. Associations between 120-d milk yield and reproductive outcome were complicated by interactions with 120-d protein percentage and calving age, depending on the breed and outcome. In general, we found that the reproductive performance of high milk-yielding animals deteriorated faster with age than low milk-yielding animals, and high protein percentage exacerbated the differences between low and high milk-yielding animals. Climate-related factors were also associated with fertility, with a 1-unit increase in maximum THI decreasing first service conception rate by 1.2% for Holstein-Friesians but having no statistically significant association in the Jersey breed. However, THI had a negative association in both breeds on the daily hazard of calving. Our study validates the efficacy of the daughter fertility EBV for improving herd reproductive performance and identifies significant associations between 120-d milk and protein yields and THI on the fertility of Australian dairy cows.

Fur removal promotes an earlier expression of involution-related genes in mammary gland of lactating mice

Peak lactation occurs when milk production is at its highest. The factors limiting peak lactation performance have been subject of intense debate. Milk production at peak lactation appears limited by the capacity of lactating females to dissipate body heat generated as a by-product of processing food and producing milk. As a result, manipulations that enhance capacity to dissipate body heat (such as fur removal) increase peak milk production. We investigated the potential correlates of shaving-induced increases in peak milk production in laboratory mice. By transcriptomic profiling of the mammary gland, we searched for the mechanisms underlying experimentally increased milk production and its consequences for mother-young conflict over weaning, manifested by advanced or delayed involution of mammary gland. We demonstrated that shaving-induced increases in milk production were paradoxically linked to reduced expression of some milk synthesis-related genes. Moreover, the mammary glands of shaved mice had a gene expression profile indicative of earlier involution relative to unshaved mice. Once provided with enhanced capacity to dissipate body heat, shaved mice were likely to rear their young to independence faster than unshaved mothers.