Review of the impact of heat stress on reproductive performance of sheep

One health agriculture: Heat stress mitigation dilemma in agriculture

The concept of One Health was developed as a successful strategy for addressing global crises that impact the health of animals, humans, and plants. The agriculture industry is facing a huge dilemma due to climate change and the impacts of heat stress, which might pose a threat to mankind in the future. In order to enhance the management of heat stress in the agriculture sector (Agri-heat stress), we suggest implementing the One Health approach. This is because the existing methods employed to alleviate heat stress in both livestock and crop farming may have side-effects on the well-being of animals, plants, humans, and the ecosystem. This review article examines the "dilemma" of mitigating heat stress in animal and crop husbandry. It discusses the One Health approach to heat stress, including a recommended strategy for reducing Agri-heat stress using the One Health approach. The study also highlights the benefits of adopting the One Health approach in mitigating Agri-heat stress. In our opinion, the efficacy of the One Health Approach in reducing Agri-heat stress depends on the process of conceptualization. This process includes recognizing the issue or hypothesis, as well as incorporating cooperating teams in the creation of environmentally friendly approaches. The efficacy and challenges of implementing this notion arise from the precise coordination of resources and collaborators.

Heat stress affects the functionality of the ovine cumulus-oocyte complex and subsequent in vitro embryo production

Global population growth requires an increase in the production of food, particularly meat, with an expected increase in sheep farming. However, climate change challenges livestock management, with heat stress negatively impacting reproductive performance. In vitro embryo production (IVP) in sheep farming is promising, although optimizing embryo quality and efficiency remains challenging. Heat stress impairs oocyte developmental competence, affecting IVP outcomes. This study investigated the effects of season on oocyte quality and embryo production given seasonal variations in the temperature and temperature-humidity index (THI) and in vitro-induced heat stress. In the first experiment, ovaries were collected in four seasons (winter, spring, summer and autumn), with differences in THI, and in the second experiment, ovaries were exposed to 30 °C (control), 38.5 °C, 40 °C and 41 °C. The results indicated that elevated summer temperatures significantly compromised oocyte and cumulus cell viability, DNA integrity, mitochondrial distribution, and blastocyst quality. These detrimental effects persisted into autumn, likely due to a carry-over effect from summer heat stress. Furthermore, in vitro exposure to temperatures at or above 38.5 °C led to marked decreases in oocyte quality and blastocyst rates. Understanding these effects is essential for developing strategies to mitigate heat stress and enhance reproductive outcomes in sheep.

Effect of heat stress on milk production traits and milk coagulation properties in dairy sheep

Heat stress in farmed animals is becoming a problem of great importance even in temperate climates, especially due to the increase in average global temperatures. Previous studies conducted on sheep have reported negative effects of heat stress on milk yield and composition and on the cheesemaking properties. The study of the effect of heat stress in sheep is complicated by the seasonality of calving and the overlap of the effects of the lactation stage with those of the climate. The aim of this work was to study the effects of heat stress in dairy sheep through a repeated measures model, separating the lactation stage and climate effects. The dataset included 2,695 repeated measurements of 555 Sardinian sheep, raised in 34 farms in Sardinia. The analyzed phenotypes were milk yield, fat, protein, lactose and somatic cell contents, milk coagulation properties (rennet clotting time, curd firming time, curd firmness), and individual laboratory cheese yield (ILCY). Temperature and humidity values of the day of the survey and of the 3 previous days were provided by the regional agency for the protection of the environment (Agenzia Regionale per la Protezione dell'Ambiente of the Sardinia Region). Climate data were then used to calculate the respective temperature and humidity indices. The effect of the temperature-humidity index (THI) was evaluated using a linear mixed model that considered stage of lactation (DIM), parity, maximum value of hourly THI calculated over 24 h (THImax) class (divided into quartiles), DIM × THI interaction, and sampling date; the farm and the animal were considered random effects. The DIM × THI interaction was significant for all parameters except somatic cells and curd firmness. Milk yield showed an increase from the first to the third THImax class and a reduction in the fourth class (THI > 73); this trend was the same in the 3 lactation stages (early, mid, and late). Fat content showed an opposite trend, independent of the lactation stage. Proteins decreased linearly at the beginning and mid lactation whereas they showed no significant changes at the end of lactation. Lactose was reduced in the fourth class of THImax, both in mid and late lactation. Rennet clotting time showed different patterns depending on DIM, whereas ILCY showed worse values as THImax increased, especially in early and mid lactation. The study of THI in the different phases of lactation made it possible to separate the 2 effects on the parameters studied and highlighted how in dairy sheep, heat stress leads to a reduction in production and a general worsening of the quality of the milk.

Inclusion of planetary health in developmental biology education

Planetary Health is an emerging multidisciplinary research field and paradigm, centred on the interactions and interdependence of human health, animal and plant ecosystems, and the state of the natural environment. In the field of Developmental Biology education, this type of broad perspective aligns with multiple areas and concepts, including the developmental origins of health and disease, effects of teratogens on embryonic development, and the impact of climate change on both animal and human populations. Academics and undergraduate students undertaking a major in Anatomy and Developmental Biology worked together to co-design a workshop for third year undergraduate students on planetary health in a final semester Developmental Biology subject. Pre and post student surveys showed significant improvements in student knowledge, attitudes and self-efficacy regarding planetary health, indicating the efficacy of this education activity. This workshop exemplifies how educators can respond to urgent calls to better equip our future workforce. Future iterations of this workshop will emphasise student-led foci on local and feasible changes to improve the sustainability of biomedical science education and research, and expand the inclusion of Indigenous perspectives, critical to improving planetary health. Incorporating knowledge of Planetary Health and Indigenous perspectives into the discipline of Developmental Biology exposes students to critical and global challenges that emerging scientists will need to address.

Impact of early life exposure to heat and cold on linguistic development in two-year-old children: findings from the ELFE cohort study

BACKGROUND

A number of negative developmental outcomes in response to extreme temperature have been documented. Yet, to our knowledge, environmental research has left the question of the effect of temperature on human neurodevelopment largely unexplored. Here, we aimed to investigate the effect of ambient temperature on linguistic development at the age of 2 years-old.

METHODS

We used data from the prospective national French birth cohort ELFE (N = 12,163) and highly-resolved exposure models with daily temporal resolution and 200 m to 1 km spatial resolution. We investigated the effect of weekly averages of overall, daytime and night-time temperature in the prenatal (first 30 weeks of gestation) and postnatal (91 weeks after birth) period on vocabulary production scores from the MacArthur-Bates Communicative Development Inventories (MB-CDI) at 2 years-old. Exposure-response and lag-response relationships were modeled with confounder-adjusted distributed lag non-linear models.

RESULTS

Scores at the MB-CDI decreased by 3.2% (relative risk (RR) 0.968, 95% confidence interval (CI): 0.939-0.998) following exposure to severe night-time heat of 15.6 °C (95th percentile) vs. 8.3 °C (median) throughout gestational weeks 14 to 19. In the postnatal period, scores at the MB-CDI decreased by 14.8% (RR 0.852; 95% CI: [0.756-0.96]) for severe overall heat of 21.9 °C (95th percentile) vs. 11.5 °C (median) throughout weeks 1 to 28. Consistent results were found for daytime and night-time heat. We observed positive effects of overall and night-time heat in the first few weeks of pregnancy. Night-time cold in the pre-natal period also resulted in improved scores at the MB-CDI. Adjusting our models for air pollutants (PM2.5, PM10 and NO2) tended to confirm these observations. Finally, there were no significant differences in temperature effects between boys and girls.

CONCLUSION

In this large cohort study, we showed a negative impact of hot temperatures during pregnancy and after birth on language acquisition. Positive associations observed in the first few weeks of pregnancy are likely the results of methodological artifacts. Positive associations with night-time cold during the prenatal period are likely truly protective, as colder temperatures may encourage staying indoors at a comfortable temperature. Policymakers should consider neurodevelopment impairments as a deleterious effect of climate change.

Physiological responses of Munjal sheep to variations in temperature humidity index in subtropical climate

Understanding the relationship between physiological parameters of livestock and temperature humidity index (THI) is essential for developing effective management strategies aimed at mitigating heat stress, especially during periods of elevated temperatures. The present study examined the physiological parameters of rectal temperature (RT), respiration rate (RR), and pulse rate (PR) in Munjal sheep reared in a subtropical climate, focusing on their association with THI. Data were collected from 29 female Munjal sheep at 15-day intervals, during morning (8:00 a.m.-10:00 a.m.) and afternoon (2:00 p.m.-4:00 p.m.) over one year. Results showed that RT was significantly higher in the afternoon compared to the morning for both lambs and adults. Likewise, RR and PR were elevated in the afternoon across both groups. In young lambs, RT (r = 0.86) and RR (r = 0.71), and in adults, RR (r = 0.89) and PR (r = 0.91) demonstrated a significant positive correlation (P < 0.05) with THI. These findings indicate that higher physiological parameters during hotter periods necessitate additional care for young lambs. In conclusions, this study highlighted the critical need for targeted management practices to support the physiological well-being of Munjal sheep in subtropical climates, particularly during periods of high temperature humidity index, ensuring optimal health and productivity.

Genetic and Epigenetic Adaptation Mechanisms of Sheep Under Multi-Environmental Stress Environment

Sheep (Ovis aries), domesticated from wild Asian mouflon ~10,000 years ago, are an important livestock species adapted to various ecological environments. Recent advancements in high-throughput sequencing and global environmental databases have facilitated the exploration of genetic-environmental associations, uncovering the genetic and epigenetic mechanisms behind sheep's adaptation to multiple environments. Studies show that HIF-1α and EPAS1 enhance high-altitude adaptation via hypoxic stress regulation; UCP1 contributes to cold adaptation through non-shivering thermogenesis; SLC4A4 and GPX3 increase drought resistance by regulating renal water reabsorption; and SOCS2 likely plays a role in metabolic and stress response regulation. Additionally, sheep adapt to temperature, drought, and environmental stress through DNA methylation, transcriptional regulation (e.g., SOD1, GPX4), heat shock proteins (e.g., HSP70), and metabolic pathways (e.g., UCP1). These findings offer valuable insights for improving sheep breeding and genetic enhancement. This review summarizes the mechanisms of adaptation to high altitude, cold, heat, drought, and comprehensive climate stress.

Rhodotorula Yeast Culture Improved the Antioxidant Capacity, Lipid Metabolism, and Immunity of Sheep Livers

There is currently no research on the application evaluation of R. mucilaginosa yeast culture (RYC) in animal production. Therefore, this study investigated the effects of RYC on the antioxidant capacity, lipid metabolism, and immunity of sheep livers. Twenty-four 3-month-old Duhan male sheep (36 ± 4 kg) were divided into four groups. The control group received a basal diet, the L group received a basal diet + 10 g/sheep/day RYC, the M group received a basal diet + 20 g/sheep/day RYC, and the H group received a basal diet + 40 g/sheep/day RYC. The trial lasted for 75 days. The results showed that the content of glutathione peroxidase in the livers of sheep in group M was significantly increased by 26.6%, and the content of malondialdehyde was significantly decreased by 38% (p < 0.05). Additionally, the serum levels of total cholesterol, triglycerides, high-density lipoprotein cholesterol, and low-density lipoprotein cholesterol significantly decreased; the liver content of C16:0 decreased; and the levels of C18:2n6C and C20:1 increased (p < 0.05). Furthermore, the contents of cytokines TNF-α and IFN-γ in sheep livers from the M group were also significantly decreased by 20% and 24.8%, respectively (p < 0.05). These findings suggest that supplementation with 20 g/sheep/day RYC can enhance antioxidant capacity, improve lipid metabolism, and reduce inflammation in sheep livers, which is advantageous for farming healthy sheep.

Effects of heat stress on reproduction and gene expression in sheep

Small ruminant farming plays a pivotal role in agriculture, especially in developing countries due to sheep's diverse functions and capacity to acclimate to varying temperatures. This review comprehensively explored the impact of rising temperatures on reproductive processes, reproductive function encoding gene expression, and sheep's ability to adapt to heat stress. Several mechanisms contribute to sheep's resilience to heat stress, encompassing morphological, behavioral, physiological, and genetic adaptations. It has been shown that heat stress compromises fertility by affecting follicular development, ovulation rate, estrous behavior, rates of conception, embryonic survival, and fetal development, while also disrupting sperm production and motility, and increasing the incidence of structurally abnormal sperm in males. Estimates suggested that heat stress may reduce conception rates from 20% to 27%. Essential genes encoding the Gonadotrophin-releasing hormone, Follicle-stimulating hormone receptor, Luteinizing hormone receptor, Estradiol receptor, progesterone receptor, and Inhibin play a critical role in elucidating how heat stress impacts the reproductive performance of sheep. Furthermore, the resilience of sheep in facing heat stress adversities is associated with a specific heat shock factor. When an animal is under heat stress, Heat shock factors get activated and stimulate the production of Heat Shock Proteins (HSPs). Emphasis should be given to identifying specific genes and candidate genes that confer protection against heat stress and conducting comprehensive research to unravel how sheep adapt to demanding local climatic conditions to enhance production and profitability, improve animal welfare, and for genetic conservation and breeding programs.

Semen Quality, Testicular Cell Apoptosis, and Transcriptome Analysis Following Mild Scrotal Heat Stress in Wugu-Hu Crossbred and Hu Rams

Hu and Wugu × Hu rams underwent scrotal insulation to simulate mild heat stress, resulting in a 3.0 ± 0.1 °C increase in scrotal surface temperature. Semen samples were collected every five days from day 11 to 56, and testis samples immediately after insulation. Both breeds experienced similar semen quality reductions and recovery trends, including reduced motility, concentration and the percentage of morphologically normal, but on days 41 and 46, Wugu-Hu rams exhibited significantly lower sperm motility than Hu rams (p < 0.05). Wugu-Hu rams demonstrate more transcriptomic changes. Further GO analysis revealed enrichment in spermatogenesis-related processes, while KEGG analysis identified Oocyte meiosis and cell cycle pathways, with a downregulation of key genes (CDK1, CDK2, CDC20, and PLK1) indicating impaired meiosis in Wugu-Hu rams. In contrast, Hu rams showed minimal transcriptional changes, contrary to the transcriptomic results. The significantly increased apoptosis rate of Wugu-Hu sheep testicular cells (p < 0.05) suggests compensatory or post-transcriptional mechanisms mitigating functional impacts caused by transcriptomic changes. The conclusion is that mild scrotal heat stress affects sperm quality and testicular gene expression. Wugu-Hu rams demonstrate greater transcriptomic sensitivity, but this does not show significant differences in semen quality recovery due to the compensatory mechanism of cell apoptosis.

METTL3 and FTO Regulate Heat Stress Response in Hu Sheep Through Lipid Metabolism via m6A Modification

In an established hepatocyte lipid deposition heat stress model, the expression levels of METTL3 and FTO were significantly upregulated (p < 0.05), indicating that METTL3 and FTO play important roles in the process of lipid deposition heat stress in hepatocytes. Transcriptome and metabolome analyses showed that lipid deposition heat stress had significant effects on the linoleic acid, linolenic acid, glycerophospholipid, and arachidonic acid metabolic pathways in hepatocytes. After METTL3 knockdown, the m6A methylation level decreased, but the difference was not significant (p > 0.05), the FABP4 and Accα expression levels increased, and the HSP60, HSP70, and HSP110 expression levels decreased significantly. After METTL3 overexpression, the m6A methylation level increased significantly and the expression levels of FABP4, ATGL, Accα, HSP60, HSP70, HSP90, and HSP110 decreased significantly, indicating that the overexpression of METTL3 reduced the expression of heat shock genes by inhibiting the lipid-deposition-related gene expression in an m6A-dependent manner. The m6A methylation level increased significantly after FTO knockdown, while HSP60, HSP110, FABP4, ATGL, and Accα expression levels were significantly reduced. Following FTO overexpression, the m6A methylation level and HSP60, HSP90, and HSP110 expression levels significantly decreased, while the ATGL and Accα expression levels significantly increased. This indicates that the overexpression of FTO promoted the expression of lipid-deposition-related genes in an m6A-dependent manner to reduce the expression of heat shock genes. Transcriptome and metabolome sequencing screened a large number of differential genes and metabolites, and a KEGG enrichment analysis showed that m6A methylation mainly regulated heat stress by affecting the TNF, cAMP, MAPK, lipolysis, and synthesis pathways in hepatocytes. In the lipid deposition heat stress model of preadipocytes, the regulation of gene expression was similar to that in hepatocytes.

Putative effects of moringa oil or its nano-emulsion on the growth, physiological responses, blood health, semen quality, and the sperm antioxidant-related genes in ram

Phytochemicals have been effectively used to enhance the growth and productivity of farm animals, while the potential roles of essential oils and their nano-emulsions are limited. This plan was proposed to investigate the impacts of orally administered moringa oil (MO) or its nano-emulsion (NMO) on the growth, physiological response, blood health, semen attributes, and sperm antioxidant-related genes in rams. A total of 15 growing Rahmani rams were enrolled in this study and allotted into three groups. The 1st control group received a basal diet only and treated orally one mL of distilled water, while the 2nd, and 3rd groups received a basal diet and were orally treated with 1 mL of NMO or 2 mL of MO /head/day for 4 months, respectively. Growth, physiological response, blood health, semen quality, and antioxidant genes in sperm were assessed. The MO and NMO treatments had no significant effect on growth indices (final body weight and weight gain ) and physiological response (rectal temperature, pulse, and respiration rates) (P > 0.05). The NMO group had the lowest levels of MCV (mean corpuscular volume) (P < 0.05), while all treated groups produced higher levels of mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC) compared to those in the control group (P < 0.05). Aspartate transferase (AST) and total cholesterol were significantly reduced in the MO and NMO groups, while total protein and glucose levels were significantly improved in NMO group (P < 0.05). Serum and seminal interstitial-cell-stimulating hormone (ICSH) levels were significantly improved (P < 0.0001) in the NMO group. Testosterone in serum and seminal plasma was significantly improved (P < 0.0001) in the MO group. Total antioxidant capacity (TAC) levels showed a tendency to increase in both the MO and NMO groups, but this increase was not significant compared to the untreated group (P > 0.05). On the other hand, the MO group exhibited lower levels of AST and malondialdehyde (MDA), while the alanine aminotransferase (ALT) levels were the lowest in the NMO group (P > 0.05). Mass motility, viability, membrane integrity and sperm concentration were significantly improved in the MO group (P < 0.0001) compared to the other groups. The NMO group had worse expressions of superoxide dismutase 1 (SOD1) compared to the control and MO groups. MO group significantly upregulated the catalase gene compared to the other groups (P < 0.001). The expression of Caspase-3 was highest in the group that received NMO compared to the other groups (P < 0.001). This study suggests that MO may serve as a novel therapeutic agent for improving the reproductive health in Rahmani rams.

The Protective Effects of Melatonin on Hainan Black Goats Under Heat Stress: Understanding Its Actions and Mechanisms

As the global climate changes, high temperatures will cause heat stress, which significantly affects the productive efficiency of livestock. Currently, there is a lack of efficient methods to use in targeting this issue. In this study, we report that melatonin supplementation may represent an alternative method to reduce the negative impact of heat stress on livestock, particularly in Hainan black goats. Our results show that melatonin treatment increased the average daily gain of Hainan black goats that were exposed to constantly high temperatures for two months compared to controls. Our mechanistic exploration revealed that melatonin treatment not only reduced the oxidative stress and inflammatory reaction caused by heat stress but also improved goats' metabolic capacity, promoting their growth and development. More importantly, for the first time, we observed that melatonin treatment modified the abundance of the intestinal microflora, altering the metabolism of the goats, which further improved their tolerance to constant heat stress.

Late gestation heat stress alters O2 regulation in placenta and neonatal heifers

INTRODUCTION

Maternal hyperthermia (i.e. heat stress) can adversely affect placental development and function, with severity varying based on pregnancy stage. During the last half of pregnancy, cow uterine blood flow increases 4.5-fold, and decreased maternal blood circulation can reduce placental diffusion capacity, impacting fetal growth.

MATERIAL AND METHODS

Milk removal was discontinued (i.e. dried off) in multiparous pregnant Holstein cows 54 ± 5 days before expected calving and assigned to cooling (CLD) or heat stress (HT) treatments. Oxygen measurements were taken within ±3 h after birth (n = 7 per group) using the Rad-G Pulse Oximeter. RNA sequencing of cotyledonary tissue examined pathways and genes related to gas and oxygen transport.

RESULTS

Heifers exposed to late gestation in utero hypoxia (HT) had significantly lower oxygen saturation at birth compared with those from dams with normal (CLD) oxygen levels (83.4 % vs. 90.7 %, p = 0.03). The peripheral index of oxygen diffusion was also lower in HT-exposed heifers (2.04 % vs. 4.84 %, p = 0.01). Gene enrichment analysis of cotyledonary tissue revealed affected pathways, including response to hypoxia, oxygen transport, and VEGF signaling. Late gestation HT potentially influenced blood circulation and nitric oxide biosynthesis pathways, with various genes showing upregulation and downregulation.

DISCUSSION

The placenta is vital for fetal development, and late gestation hyperthermia can significantly affect its function, reducing fetal oxygen delivery and altering genes regulating placental gas and oxygen transport. These disruptions may result in fetal hypoxemia and growth restriction.

Acute heat stress regulates estradiol synthesis in ovine ovarian granulosa cells through the SREBPs/MVK-LHR pathway

The adverse effects of heat stress on reproductive performance of sheep are becoming increasingly severe. Previous research has revealed that heat stress decreases both cholesterol and estradiol content; however, regulation of estradiol by cholesterol and its regulatory mechanism under heat stress are unclear. Mevalonate kinase (MVK), a key cholesterol synthesis pathway enzyme, binds to the luteinizing hormone receptor (LHR; a key gene regulating hormone synthesis) mRNA. In this study, ovine ovarian granulosa cells (GCs) were used in an in vitro model. To elucidate the underlying molecular mechanism, immunofluorescence, quantitative reverse transcription polymerase chain reaction, western blotting, enzyme-linked immunosorbent assay, and an RNA electrophoretic mobility shift assay (REMSA) were used to investigate whether the decrease in cholesterol caused by acute heat stress resulted in a decrease in estradiol synthesis. Acute heat stress reduced the cholesterol content in ovine ovarian GCs, which transactivated the cholesterol synthesis pathway corresponding to the gene expression of sterol regulatory element-binding protein (SREBP-1A), SREBP-2, and MVK. Upregulated MVK increased the MVK-LHR mRNA complex, which caused LHR mRNA decay and downregulation, further leading to the downregulation of CYP19A1 and a decrease in estradiol. The cholesterol synthesis inhibitor, PF-429242, alleviated the decrease in estradiol synthesis caused by acute heat stress. Overall, acute heat stress caused a decrease in total cholesterol, which transactivated the expression of cholesterol synthesis genes, such as SREBP-1A, SREBP2, and MVK, increasing the MVK-LHR complex, downregulating LHR expression, and further decreasing estradiol.

Heat stress: a major threat to ruminant reproduction and mitigating strategies

Stress is an external event or condition that puts pressure on a biological system. Heat stress is defined as the combination of internal and external factors acting on an animal to cause an increase in body temperature and elicit a physiological response. Heat stress is a set of conditions caused by overexposure to or overexertion at excess ambient temperature and leads to the inability of animals to dissipate enough heat to sustain homeostasis. Heat exhaustion, heat stroke, and cramps are among the symptoms. For the majority of mammalian species, including ruminants, heat stress has a negative impact on physiological, reproductive, and nutritional requirements. Reproductive functions, including the male and female reproductive systems, are negatively affected by heat stress. It decreases libido and spermatogenic activity in males and negatively affects follicle development, oogenesis, oocyte maturation, fertilization, implantation, and embryo-fetal development in females. These effects lead to a decrease in the rate of reproduction and financial losses for the livestock industry. Understanding the impact of heat stress on reproductive tissues will aid in the development of strategies for preventing heat stress and improving reproductive functions. Modification of the microenvironment, nutritional control, genetic development of heat-tolerant breeds, hormonal treatment, estrous synchronization, timed artificial insemination, and embryo transfer are among the strategies used to reduce the detrimental effects of heat stress on reproduction. These strategies may also increase the likelihood of establishing pregnancy in farm animals.

Late-gestation heat stress alters placental structure and function in multiparous dairy cows

The placenta plays a pivotal role in fetal development and the dam's subsequent lactation performance, because it facilitates nutrient transfer, heat dissipation, and gas exchange with the growing fetus, and regulates key hormones essential for mammary gland development. Heat stress experienced during gestation and lactation can significantly reduce the placenta's capacity to perform these critical functions. To investigate the impact of heat stress, trials were conducted over the summer months of 2020, 2022, and 2023 in Florida. Multiparous pregnant Holstein cows were dried off 54 ± 5 d before their expected calving date and randomly assigned to 1 of 2 treatments for the entire dry period: active cooling (CL; access to barn shade, natural ventilation plus forced air circulation via fans, and water soakers; n = 20) or heat stress (HT; access to barn shade and natural ventilation; n = 20). Gestation length and calf birth weights were recorded. Placentas were collected from a subset of cows shortly after calving (4.00 ± 1.54 h; n = 10/treatment) and analyzed for total placental weight, as well as cotyledon weight, number, and surface area within 1 h after expulsion. A representative cotyledon sample was isolated for histological analysis. Tissues were also processed for RNA sequencing and DNA methylation analysis. DNA methylation was analyzed by double restriction enzyme reduced representation bisulfate sequencing. Differentially methylated cytosines between HT and CL were identified via logistic regression with a cut-off value of 15% methylation difference and a q-value <0.2. Morphological and histological data were analyzed using generalized linear mixed models. Results indicate that gestation length was shorter in HT cows compared with CL cows (274.2 vs. 277.2 ± 1.46 d), and heifers born to HT dams were lighter at birth (31.4 vs. 34.8 ± 1.59 kg). Placentas from HT dams tended to have lower total weight (3.54 vs. 4.54 ± 0.38 kg) and fewer cotyledons (66.2 vs. 103.3 ± 8.65). However, placental efficiency was higher in the HT versus CL group (11.5 vs. 8.52 ± 0.91%). Cotyledons from HT cows had greater vascular area (43.1% vs. 31.8% ± 10.4% of total area) and a tendency for less connective tissue (52.7% vs. 65.8% ± 5.39% of total area). A total of 289 differentially expressed genes were identified between HT and CL placentas, with 179 upregulated and 110 downregulated in the HT group. Key genes affected included NPSR1, SPATC1L, PGF, HSPB8, IL6, HBA/HBB, MMP12, PAPPA2, PAG14, and SLC7A10. Dysregulated pathways in HT placentas involved gas and oxygen transport, nutrient transport, inflammatory response, and cortisol biosynthesis. Heat stress induced hypermethylation of regulatory pathways, including collagen biosynthesis and degradation, extracellular matrix structural components, and placental tissue organization. Our findings demonstrate that late-gestation HT causes significant transcript alterations in the placenta, leading to adaptations for thermoregulation and morphological changes. These alterations negatively affect birth weight, health, and dam lactation performance, underscoring the need to address HT during late gestation to ensure optimal fetal development and postnatal outcomes. Addressing these issues can help improve dairy cow resilience to climate change, enhancing animal welfare and productivity.

Pomegranate peels ethanolic extract in free and nanoemulsified forms around mating and early pregnancy differently affect heat tolerance capacity and reproductive performance of ewes under heat stress

Global warming is seriously threatening sheep farmings by increasing health problems and decreasing reproductive efficiency. In this study, pomegranate peels ethanolic extract (Ppee), rich in phenolic acids, was prepared in free (Fppee) and nanoemulsified (Nppee, with 18.49 nm-21.8 nm particles size) forms. The protective role of the extracts against heat stress impacts on homeothermy, metabolism and redox status, and reproductive performance of ewes was studied. A total of 36 Barki ewes were synchronized to estrus using two intramuscular injections PGF2α. On the day of the first PGF2α, ewes were allocated into three homogeneous experimental groups and received 300 mg/ewe/day Fppee, 300 mg/ewe/day Nppee, or not (control) until day 35 post-mating. The Fppee ewes showed the highest homeothermy in the morning, whereas the Nppee ewes showed the lowest homeothermy in the afternoon (P < 0.001). Both extracts increased plasma total protein, glucose, total antioxidant capacity, and glutathione concentrations (P < 0.001), whereas they decreased plasma urea, cholesterol, and malondialdehyde concentrations compared to control (P < 0.001). The highest and lowest values of these variables were for the Nppee ewes. The Nppee ewes had the significant lowest plasma progesterone concentrations. There were no differences in corpora lutea numbers and diameters. Lambs born to Fppee ewes had the highest birth weights and survivability. In conclusion, supplementing heat-stressed ewes with Fppee improved homeothermy, metabolism, redox status, and lamb weight and survivability without hampering reproductive performance, mainly by decreasing progesterone concentrations as observed in Nppee ewes.

Reproductive mechanisms, pathologies, and health inclusivity: insights from the 2023 Annual Meeting of the Society for Reproductive Biology

In 2023, the Society for Reproductive Biology met in Brisbane to deliver its largest scientific program to date. Herein, we detail key areas of notable discovery across the reproductive biology and fertility landscapes, as well as pressing areas that require further research. Specifically, we focus on five key themes: the cellular basis of reproduction; environmental impacts on reproduction; inclusivity in reproductive health; reproductive cancers; and evolution of reproduction mechanisms. Highlights included the utility of organism models, such as using fruit flies to model human genetic disease, and the development of new blastocyst models; the impact of elevated temperature and endocrine-disrupting chemicals on the germline, sex organ development, and fertility in mammals; how we can improve the inclusivity of transgender and Pacific Rainbow+ people in reproductive health; novel insights in reproductive cancer pathogenesis and inhibitor treatments; and the evolution of the sex chromosomes and sex determination across animals. The breadth of topics covered underscores the far-reaching impacts of reproduction and its related processes across life, health, and wellbeing, as well as for food production and the economy.

The interrelationship between macrominerals and heat stress in ruminants: current perspectives and future directions - a review

Macromineral imbalances in ruminants, particularly in tropical and subtropical regions, pose a significant challenge to production sustainability and profitability. Heat stress exacerbates these imbalances, negatively impacting physiological functions and productivity. This review examines the effects of heat stress on macromineral levels in ruminants and the need for supplementation under such conditions. Heat stress lowers key macrominerals (Na+, K+, Cl-, Ca + 2, Mg + 2, inorganic P) and disrupts acid-base balance due to thermoregulatory responses and reduced feed intake. Supplementing macrominerals to the diet to achieve higher dietary cation-anion difference helps mitigate heat-related morbidity and maintains ruminant health and productivity. A more practical approach, such as sustained-release macromineral boluses in the rumen, is proposed to provide more consistent benefits. Further researches are warranted to optimize supplementation strategies and fully understand macromineral nutrition for heat-stressed ruminants.

Expression profiles of circulating miRNAs in an endangered Piedmontese sheep breed during the estrus cycle

Introduction

The preservation of locally endangered breeds is essential for maintaining ecosystem services that benefit both society and the environment. Reproductive fitness becomes a crucial consideration in this context. MicroRNAs (miRNAs) are small non-coding RNA molecules that play a key role in post-transcriptional regulation. Typically, they function within the tissues where they are produced. However, when they are released into extracellular fluid, they are referred to as circulating miRNAs (c-miRNAs). C-miRNAs may serve as potential biomarkers, whose profile changes under different physiological states. The purpose of this study is to establish a connection between distinctive variations in the expression of c-miRNAs and specific estrus cycle phases in Frabosana-Roaschina sheep, an endangered Piedmontese breed.

Methods

Two trials, each involving 20 ewes with different reproductive efficiencies (nulliparous in the first trial and pluriparous in the second trial), were sampled on alternate days after synchronization for blood, saliva, and feces. Ultrasound scans were performed during the induced estrus cycle. The animals' behaviors were assessed through video recordings.

Results

In the first trial, play behaviors were detected without sexual behaviors, whereas in the second trial, sexual behaviors were observed without play behaviors. Based on plasma trends of 17β-estradiol and progesterone and ultrasound images, two moments were identified for miRNAs analyses: the beginning of the follicular phase (day 2) and the beginning of the luteal phase (day 11). C-miRNAs of six representative animals from the second trial were sequenced. Analyses of the sequencing data have identified 12 c-miRNAs that were differentially expressed (DE) when comparing day 11 with day 2: five miRNAs were found to be upregulated, whereas seven miRNAs were downregulated. An enrichment analysis, based on predicted targets, using the Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) databases was performed. Many of these genes regulate reproductive pathways with the possible involvement of miRNAs. Finally, qRT-PCR was conducted to validate the DE miRNAs in all ewes. Differences in gene expression between the two sampling points and the two trials were observed, in line with existing literature.

Discussion

Investigating the role of these miRNAs in regulating estrus could improve the reproductive performance and welfare of Frabosana-Roaschina ewes.

Environmental Heat Stress Decreases Sperm Motility by Disrupting the Diurnal Rhythms of Rumen Microbes and Metabolites in Hu Rams

Heat stress (HS) has become a common stressor, owing to the increasing frequency of extreme high-temperature weather triggered by global warming, which has seriously affected the reproductive capacity of important livestock such as sheep. However, little is known about whether HS reduces sperm motility by inducing circadian rhythm disorders in rumen microorganisms and metabolites in sheep. In this study, the year-round reproduction of two-year-old Hu rams was selected, and the samples were collected in May and July 2022 at average environmental temperatures between 18.71 °C and 33.58 °C, respectively. The experiment revealed that the mean temperature-humidity index was 86.34 in July, indicating that Hu rams suffered from HS. Our research revealed that HS significantly decreased sperm motility in Hu rams. Microbiome analysis further revealed that HS reshaped the composition and circadian rhythm of rumen microorganisms, leading to the circadian disruption of microorganisms that drive cortisol and testosterone synthesis. Serum indicators further confirmed that HS significantly increased the concentrations of cortisol during the daytime and decreased the testosterone concentration at the highest body temperature. Untargeted metabolomics analysis revealed that the circadian rhythm of rumen fluid metabolites in the HS group was enriched by the cortisol and steroid synthesis pathways. Moreover, HS downregulated metabolites, such as kaempferol and L-tryptophan in rumen fluid and seminal plasma, which are associated with promotion of spermatogenesis and sperm motility; furthermore, these metabolites were found to be strongly positively correlated with Veillonellaceae_UCG_001. Overall, this study revealed the relationship between the HS-induced circadian rhythm disruption of rumen microorganisms and metabolites and sperm motility decline. Our findings provide a new perspective for further interventions in enhancing sheep sperm motility with regard to the circadian time scale.

N-Acetylcysteine assists muscle development in offspring of mice subjected to maternal heat stress during pregnancy

BACKGROUND

Heat stress (HS) has been shown to affect reproductive performance and muscle development negatively in animals. N-Acetylcysteine (NAC) plays a pivotal role in enhancing the antioxidant performance in animals as a recognized antioxidant. The present study assesses the potential of NAC to modulate the reproductive performance and antioxidant function in pregnant mice exposed to HS. The role of NAC in muscle development of offspring mice was also explored.

RESULTS

The results showed that NAC supplementation from day 12 to day 18 of gestation increased the number of litters and enhanced the antioxidant function in pregnant mice under HS exposure. It improved the weight and body condition significantly in the offspring mice (P < 0.05). The alleviation of HS-induced muscle impairment with NAC was consistent with the alleviation of apoptosis, the enrichment of the proliferation and differentiation in the offspring mice muscle. N-Acetylcysteine also reversed HS-induced reduction in the cross-sectional area of the leg muscle and increased the proportion of myosin heavy chain IIx (MYHCIIx) in the muscle fiber.

CONCLUSION

The results of the present study support the use of NAC at a dose of 100 mg kg-1 body weight as supplement for protecting the offspring derived from pregnant mice exposed to HS from muscle impairment by accelerating proliferation and differentiation. © 2024 Society of Chemical Industry.

Cervix-Deep Rectal Temperature Differential on the Day of Ovulation is Correlated With Embryo Recovery Results in Mares

Variations in temperature throughout the reproductive tract have been noted in many species. A recent study found the cervix-rectum temperature differential (CR-TD) in cattle was related to fertility. The present study aimed to assess the CR-TD in mares around the time of ovulation and relate it to embryo recover. Over 52 cycles, mares were inseminated with a fertile stallion and embryo recovery was undertaken on Day 7 post ovulation. Further 10 control mares were not inseminated. Rectal and cervical temperatures were measured using a precision thermometer on four or five occasions: the day of deslorelin administration and insemination, the day before ovulation, the day of ovulation (Day 0), the day after ovulation and, for inseminated mares, before embryo recovery on Day 7. One-way ANOVA showed that the CR-TD was significantly lower on the day of ovulation in the 36 positive cycles, in which an embryo was recovered, versus the 16 in which the embryo flush was negative (0.21 ± 0.17 vs. 0.40 ± 0.09°C; p < 0.001). Control cycles showed equivalent CR-TD to positive (0.13 ± 0.22 vs. 0.21 ± 0.17°C; p = 0.196) but not negative cycles (0.13 ± 0.22 vs. 0.40 ± 0.09°C; p < 0.001). A positive embryo recovery was associated with lower CR-TDs from the time of insemination and deslorelin to the day after ovulation compared to the day of embryo flushing (RM ANOVA; p < 0.001; Pairwise comparisons; p ≤ 0.01, in all cases). Rectal or cervical temperatures per se showed no significant differences between positive, negative or control cycles at any time point. In conclusion, a thermoregulatory process occurs close to ovulation which results in a lower CR-TD in cycles that produced an embryo versus those which did not. Further characterisation of TDs within the reproductive tract of the mare would increase our understanding of the conditions required for optimum fertility.

A scoping review on heat indices used to measure the effects of heat on maternal and perinatal health

A previous systematic review has shown associations between exposure to high temperatures and negative birth outcomes. To date, a scoping review for heat indices and their use to measure effects of heat on maternal and perinatal health has not been considered.

Objectives

To provide a scoping review on heat stress and indices for those interested in the epidemiology and working in extreme heat and maternal perinatal health.

Methods

This study is a scoping review based on a previous review guided by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for scoping reviews. It identifies the main ways heat stress through different heat indices impacts maternal and perinatal health in available literature. For documents that met the inclusion criteria, we extracted 23 publications.

Results

We find four heat indices: heat index, apparent temperature, wet bulb globe temperature and universal thermal climate index. Exposure to elevated levels of heat stress can be associated with preterm birth. In addition, the more intense and prolonged duration of exposure to heat stress, the greater the risk of stillbirth. Negative birth outcomes can occur from change in hormonal levels (ie, cortisol), dehydration and blood flow diversion away from the placenta and fetus when suffering from heat stress. All studies demonstrate that certain socioeconomic factors influence the effect of heat on maternal and perinatal health outcomes.

Conclusion

We make three suggestions based on the results: (1) heat indices should be standardised across studies and explained. (2) An increased number of perinatal and maternal health outcomes explored. Finally, (3) enhanced collaboration across climate and health to improve understanding.

Integration of selective sweeps across the sheep genome: understanding the relationship between production and adaptation traits

BACKGROUND

Livestock populations are under constant selective pressure for higher productivity levels for different selective purposes. This pressure results in the selection of animals with unique adaptive and production traits. The study of genomic regions associated with these unique characteristics has the potential to improve biological knowledge regarding the adaptive process and how it is connected to production levels and resilience, which is the ability of an animal to adapt to stress or an imbalance in homeostasis. Sheep is a species that has been subjected to several natural and artificial selective pressures during its history, resulting in a highly specialized species for production and adaptation to challenging environments. Here, the data from multiple studies that aim at mapping selective sweeps across the sheep genome associated with production and adaptation traits were integrated to identify confirmed selective sweeps (CSS).

RESULTS

In total, 37 studies were used to identify 518 CSS across the sheep genome, which were classified as production (147 prodCSS) and adaptation (219 adapCSS) CSS based on the frequency of each type of associated study. The genes within the CSS were associated with relevant biological processes for adaptation and production. For example, for adapCSS, the associated genes were related to the control of seasonality, circadian rhythm, and thermoregulation. On the other hand, genes associated with prodCSS were related to the control of feeding behaviour, reproduction, and cellular differentiation. In addition, genes harbouring both prodCSS and adapCSS showed an interesting association with lipid metabolism, suggesting a potential role of this process in the regulation of pleiotropic effects between these classes of traits.

CONCLUSIONS

The findings of this study contribute to a deeper understanding of the genetic link between productivity and adaptability in sheep breeds. This information may provide insights into the genetic mechanisms that underlie undesirable genetic correlations between these two groups of traits and pave the way for a better understanding of resilience as a positive ability to respond to environmental stressors, where the negative effects on production level are minimized.

Effect of Organic Selenium Supplementation on the Antioxidant Status, Immune Response, and the Relative Expression of IL-2 and IFN-γ Genes in Ewes During the Hot Season

This study was conducted to evaluate the effects of different doses of selenium (Se) from Sel-Plex© (selenium-enriched Saccharomyces cerevisiae yeast) supplement on the antioxidant status, the antibody titers against the foot-and-mouth disease virus, and the expression of interleukin-2 (IL-2) and interferon-γ (IFN-γ) genes in ewes during the hot season. Six ewes were kept at 25 °C and received basal diet (the negative control group), and 24 ewes were kept at 38 °C for 5 h per day and received no supplement (the positive control), 0.15, 0.30, and 0.45 mg Se/kg. Ewes in the positive control had higher (P<0.001) liver enzyme activity, malondialdehyde (MDA), and cortisol levels, and lower antibody titer than the negative control. The liver enzymes' lowest (P<0.001) activities were observed in ewes receiving 0.30 and 0.45 mg Se/kg. Ewes receiving 0.30 and 0.45 mg Se/kg had lower MDA levels than other treatments. Ewes receiving 0.30 and 0.45 mg Se/kg had higher (P<0.001) total antioxidant capacity levels than those receiving 0.15 mg Se/kg and the positive control. Se-supplemented groups had lower (P<0.001) relative expression of IL-2 and higher (P<0.04) expression of IFN-γ than the positive control. The antibody titer was the same in the positive control and the group receiving 0.15 mg Se/kg. Ewes fed a diet with 0.30 and 0.45 mg Se/kg had higher (P<0.011) antibody titer than the positive control. The Se supplementation can reverse the decrease of antioxidant capacity and immune function caused by heat stress, and 0.3 mg Se/kg from Sel-Plex©is the best dose.

Factors affecting the success of laparoscopic artificial insemination in sheep

Successful artificial breeding underpins rapid genetic and production gains in animal agriculture. In sheep, artificial insemination with frozen semen is performed via intrauterine laparoscopy as frozen-thawed spermatozoa do not traverse the cervix in sufficient numbers for high fertility and transcervical insemination is anatomically impossible in most ewes. Historically, laparoscopic artificial insemination has always been considered reasonably successful, but recent anecdotal reports of poor fertility place it at risk of warning adoption. Understanding the male, female and environmental factors that influence the fertility of sheep is warranted if the success of artificial insemination is to be improved and genetic progress maximised for the sheep industry. This review details the current practice of laparoscopic AI in sheep. It explores the effects of semen quantity and quality, the ewe, her preparation, and environmental conditions, on the fertility obtained following laparoscopic artificial insemination.

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.

Climate-influenced performance and offspring development of merino sheep in a dry temperate-cold valley

This study aims to explore the effects of climate on the performance and offspring development of aged Merino sheep relocated from an arid, cold environment with harsh grazing conditions to a dry, temperate-cold valley with irrigated pasture production. We utilized time series data from merino sheep in a dry temperate-cold climate in southern Argentina to characterize their growth curves, assess the impact of climate on performance, and compare offspring growth with maternal growth. Our approach involved developing a dynamic model, a non-autonomous differential equation growth curve based on the widely used Brody model. The model considered variables such as local temperature, age, sex, origin, and pregnancy status to determine the optimal combination of parameters for sheep growth in our dataset. The results have shown that moving the old sheep from the steppe to the valley resulted in an increase of an average of 1 kg in weight, but their offspring had an asymptotic weight of 65 kg, 17 kg more than their mothers. The optimum temperature for the growth rate was 15.7+/-0.56 C and 8.7+/-6.3C for the asymptotic weight.

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.

Heat stress from current and predicted increases in temperature impairs lambing rates and birth weights in the Australian sheep flock

Livestock heat stress threatens production, particularly in semi-arid, arid and tropical regions. Using established temperature thresholds for sheep, we modelled +1 °C and +3 °C temperature increases over the historical baseline, estimating that 2.1 million potential lambs are lost annually due to heat stress alone, increasing to 2.5 and 3.3 million, respectively, as temperatures rise. Heat stress poses risks at key periods of the reproductive cycle, with consequences across the Australian sheep flock.

Bioclimatic thermal stress indices and their relationships with andrological characteristics in hair rams

This study evaluated relationships among reproductive parameters and the bioclimatic indices: temperature and humidity index (THI), equivalent temperature index (ETI), black globe temperature and humidity index (BGTHI), and thermal comfort index (TCI), during the first 45 days of spermatogenesis (SP-45) and during the 15 days of sperm transit through the epididymis (STP-15) that preceded the reproductive assessments (ReA). Such information is useful in determining the optimal breeding season in Northeast Brazil. Santa Inês rams (n = 25) underwent two ReA in three periods of the year (D-P = dry; R-P = rainy and RD-P = rainy/dry transition), and the bioclimatic indices were calculated at the corresponding SP-45 and STP-15 timepoints prior to each ReA. Sperm kinetic parameters in D-P were depressed compared to R-P and RD-P (P < 0.05). The index values had an antagonistic relationship with most parameters and regression analysis demonstrated that the BGTHI and the TCI had a negative association with the progressive motility, curvilinear, straight line, and average path velocities, and a positive association with slow sperm in the ejaculate in SP-45 and STP-15 phases (P < 0.01). Semen quality kinetics is affected throughout the year by the environment and it is apparent that it is impaired in D-P and better in R-P and RD-P seasons. The BGTHI and TCI measured in the sperm production phase classified the environment most coherently and presented better association with the behavior of sperm kinetics.

Heat stress conditions affect the social network structure of free-ranging sheep

Extreme weather conditions, like heatwave events, are becoming more frequent with climate change. Animals often modify their behaviour to cope with environmental changes and extremes. During heat stress conditions, individuals change their spatial behaviour and increase the use of shaded areas to assist with thermoregulation. Here, we suggest that for social species, these behavioural changes and ambient conditions have the potential to influence an individual's position in its social network, and the social network structure as a whole. We investigated whether heat stress conditions (quantified through the temperature humidity index) and the resulting use of shaded areas, influence the social network structure and an individual's connectivity in it. We studied this in free-ranging sheep in the arid zone of Australia, GPS-tracking all 48 individuals in a flock. When heat stress conditions worsened, individuals spent more time in the shade and the network was more connected (higher density) and less structured (lower modularity). Furthermore, we then identified the behavioural change that drove the altered network structure and showed that an individual's shade use behaviour affected its social connectivity. Interestingly, individuals with intermediate shade use were most strongly connected (degree, strength, betweenness), indicating their importance for the connectivity of the social network during heat stress conditions. Heat stress conditions, which are predicted to increase in severity and frequency due to climate change, influence resource use within the ecological environment. Importantly, our study shows that these heat stress conditions also affect the animal's social environment through the changed social network structure. Ultimately, this could have further flow on effects for social foraging and individual health since social structure drives information and disease transmission.

Heat stress and ram semen production and preservation: Exploring impacts and effective strategies

As global warming persists, heat stress (HS) continues to affect animals, particularly those raised in extensive systems such as sheep. As a result, there is a growing body of research investigating the physiological and biological consequences of HS on these animals. Recent studies have specifically examined the effects of climate change, global warming, and HS on gametes. Heat stress has been shown to affect ram semen production, resulting in decreased sperm quality and volume in both fresh and stored samples. This is attributed to the effect of heat on hormone production in the testicles, which is critical for successful spermatogenesis. Such effects can have significant consequences on the fertility of female sheep, which could affect the farmers' revenue. Therefore, farmers and researchers are utilizing various strategies and laboratory techniques to mitigate these negative effects. This review aims to comprehensively evaluate the impact of HS on ram semen production and conservation and analyze the different mitigation strategies at various levels, including management and nutritional interventions. The findings of this review will serve as a critical foundation for the development of targeted interventions and sustainable practices in sheep farming, ensuring resilient and profitable operations in the face of ongoing global climate challenges.

Seasonal heat stress compromises testicular thermoregulation and semen quality of Dorper rams raised in a desert climate

Dorper rams are widely distributed throughout the world under different climatic conditions, however, little is known about their reproductive performance in desert regions. Ten Dorper rams were individually housed and exposed to thermoneutrality for 35 d in spring (23.6 ± 5.6 °C, mean ± SD) and outdoor heat stress (HS) for 35 d in summer (33.6 ± 2.0 °C) to evaluate the effect of seasonal HS on physiological responses, testicular biometry, and seminal quality under desert climatic conditions. Rectal temperature, respiration rate and coat surface temperatures in different body regions were measured every 7 d (0600, 1200, and 1800 h); also, testicular biometry was registered at 0600 h. Semen was collected via an artificial vagina 3 d after physiological variables were measured and seminal traits were evaluated. Rectal temperature, respiration rate and coat surface temperatures were higher (P < 0.01) at each hour of measurement in summer compared to spring. Overall, scrotal length and circumference, as well as testicular volume were higher (P < 0.01) in summer than in spring. Compared to spring conditions, summer HS caused lower (P ≤ 0.05) sperm concentration and viability combined with a higher percentage of sperm abnormalities without affecting ejaculate volume. Both mass and sperm motility were similar between seasons in the first two sampling weeks, and then decreased (P ≤ 0.03) due to summer HS. In conclusion, Dorper rams developed testicle hyperthermia and, consequently, showed poor semen quality due to the high environmental temperatures prevailing in desert regions.

Dose-responses of zinc as zinc-methionine supplements on antioxidant status, hematological parameters, immune response and the expression of IL-4 and IL-6 genes of ewes in the hot season

This study was implemented to evaluate the effects of different zinc doses as Zinc-Met supplement (Zinpro®) on the antioxidant status, blood immune cells, antibody titers, and the expression of IL-4 and IL-6 genes of ewes in the hot season. In a completely randomized design, 24 ewes were assigned to treatments as follow: 0, 15, 30 and 45 mg/kg zinc as Zinc-Met supplementation for 40 days in region with 40 °C and vaccinated against food-and-mouth disease as an immune challenge at day 30, and then blood samples were collected on day 40. Ewes were fed a basal diet containing 29.9 mg zinc/kg. The highest activity of the antioxidant enzyme and the lowest lipid peroxidation values were found in ewes receiving 30 and 45 mg/kg zinc following a linear trend. The highest lymphocytes count and antibody titers were found in ewes received 30 mg zinc/kg. There were no significant differences among treatments for the relative expression of genes. In overall, zinc supplementation non-significantly up-regulate interleukin-4 and down-regulate interleukin-6. It was concluded that zinc supplementation as Zinc-Met could enhance the antioxidant status and immune response of ewes under heat stress; supplementation of diet with 30 mg zinc/kg (300 mg/kg Zinpro®) appeared to be the most effective dose.

Critical Windows of Maternal Exposure to Biothermal Stress and Birth Weight for Gestational Age in Western Australia

BACKGROUND

There is limited and inconsistent evidence on the risk of ambient temperature on small for gestational age (SGA) and there are no known related studies for large for gestational age (LGA). In addition, previous studies used temperature rather than a biothermal metric.

OBJECTIVES

Our aim was to examine the associations and critical susceptible windows of maternal exposure to a biothermal metric [Universal Thermal Climate Index (UTCI)] and the hazards of SGA and LGA.

METHODS

We linked 385,337 singleton term births between 1 January 2000 and 31 December 2015 in Western Australia to daily spatiotemporal UTCI. Distributed lag nonlinear models with Cox regression and multiple models were used to investigate maternal exposure to UTCI from 12 weeks preconception to birth and the adjusted hazard ratios (HRs) of SGA and LGA.

RESULTS

Relative to the median exposure, weekly and monthly specific exposures showed potential critical windows of susceptibility for SGA and LGA at extreme exposures, especially during late gestational periods. Monthly exposure showed strong positive associations from the 6th to the 10th gestational months with the highest hazard of 13% for SGA (HR = 1.13 ; 95% CI: 1.10, 1.14) and 7% for LGA (HR = 1.07 ; 95% CI: 1.03, 1.11) at the 10th month for the 1st UTCI centile. Entire pregnancy exposures showed the strongest hazards of 11% for SGA (HR = 1.11 ; 95% CI: 1.04, 1.18) and 3% for LGA (HR = 1.03 ; 95% CI: 0.95, 1.11) at the 99th UTCI centile. By trimesters, the highest hazards were found during the second and first trimesters for SGA and LGA, respectively, at the 99th UTCI centile. Based on estimated interaction effects, male births, mothers who were non-Caucasian, smokers, ≥ 35 years of age, and rural residents were most vulnerable.

CONCLUSIONS

Both weekly and monthly specific extreme biothermal stress exposures showed potential critical susceptible windows of SGA and LGA during late gestational periods with disproportionate sociodemographic vulnerabilities. https://doi.org/10.1289/EHP12660.

Local adaptation and future climate vulnerability in a wild rodent

As climate change continues, species pushed outside their physiological tolerance limits must adapt or face extinction. When change is rapid, adaptation will largely harness ancestral variation, making the availability and characteristics of that variation of critical importance. Here, we used whole-genome sequencing and genetic-environment association analyses to identify adaptive variation and its significance in the context of future climates in a small Palearctic mammal, the bank vole (Clethrionomys glareolus). We found that peripheral populations of bank vole in Britain are already at the extreme bounds of potential genetic adaptation and may require an influx of adaptive variation in order to respond. Analyses of adaptive loci suggest regional differences in climate variables select for variants that influence patterns of population adaptive resilience, including genes associated with antioxidant defense, and support a pattern of thermal/hypoxic cross-adaptation. Our findings indicate that understanding potential shifts in genomic composition in response to climate change may be key to predicting species' fate under future climates.

Incorporation of L-Carnitine in the OvSynch protocol enhances the morphometrical and hemodynamic parameters of the ovarian structures and uterus in ewes under summer climatic conditions

Heat stress negatively impacts the reproductive performance of sheep including the efficiency of estrous synchronization regimens. This study aimed to investigate the potential effects of L-Carnitine (LC) administration on the efficacy of the OvSynch protocol in ewes under summer climatic conditions. Ewes were synchronized for estrus using the OvSynch protocol and a dose of LC (20 mg/kg body weight) was intravenously (IV) administered on the same day of PGF2α injection to one group (n = 8; LC group), while other ewes (n = 8; control group) received the same protocol without LC. Ultrasonographic evaluation (including B-mode, color, and pulsed Doppler) was used to assess the morphometrical and hemodynamic parameters of ovarian structures [number, size, and blood flow of follicles (GFs) and corpora lutea (CLs)] and uterus during the estrous phase (Day 0), and on Day 8 post ovulation (luteal phase). Uterine artery blood flow (MUA) was assessed by measuring the resistive index (RI) and pulsatility index (PI) at both stages. The serum samples were collected to measure the concentrations of estradiol (E2), progesterone (P4), and total antioxidant capacity (TAC) using commercial kits. Results revealed a significant (P<0.05) increase in the colored pixel area of GFs and uterus in the LC group (392.84 ± 31.86 and 712.50 ± 46.88, respectively) compared to the control one (226.25 ± 17.74 and 322 ± 18.78, respectively) during Day 0. Circulating E2 and TAC levels were significantly (P<0.05) higher in the LC-treated ewes (31.45 ± 1.53 pg/ml and 1.80 ± 0.13 mM/L, respectively) compared to those in the control ewes (21.20 ± 1.30 pg/ml and 0.98 ± 0.09 mM/L, respectively) during Day 0. Moreover, LC improved the colored pixel area of CLs (2038.14 ± 102.94 versus 1098 ± 82.39) and uterus (256.38 ± 39.28 versus 121.75 ± 11.36) and circulating P4 (2.99 ± 0.26 ng/ml versus1.67 ± 0.15 ng/ml) on Day 8. Values of RI of MUA were significantly lower in the LC group compared to the control one on Day 0 and Day 8 (0.48 ± 0.03 versus 0.72 ± 0.03 and 0.58 ± 0.03 versus 0.78 ± 0.02, respectively). In conclusion, LC incorporation in the OvSynch protocol enhanced the morphometrical and hemodynamic parameters of the ovarian structures and the uterus concomitantly with improvements in the TAC, E2, and P4 concentrations in ewes under hot summer conditions.

Small RNA sequencing analysis of exosomes derived from umbilical plasma in IUGR lambs

During the summer, pregnant ewes experience heat stress, leading to the occurrence of IUGR lambs. This study aims to explore the biomarkers of exosomal miRNAs derived from umbilical plasma in both IUGR and normal Hu lambs. We establish a heat-stressed Hu sheep model during mid-late gestation and selected IUGR and normal lambs for analysis. Exosomes from umbilical plasma were separated and small RNA sequencing is used to identify differentially expressed miRNAs. Next, we utilize MiRanda to predict the target genes of the differentially expressed miRNAs. To further understand the biological significance of these miRNAs, we conduct GO and KEGG pathway enrichment analysis for their target genes. The study's findings indicate that oar-miR-411a-5p is significantly downregulated in exosomes derived from umbilical plasma of IUGR lambs, while oar-miR-200c is significantly upregulated in the HS-IUGR group (P < 0.05). Furthermore, GO and KEGG enrichment analysis demonstrate that the target genes are involved in the Wnt, TGF-beta, and Rap1 signaling pathways. miRNAs found in exosomes have the potential to be utilized as biomarkers for both the diagnosis and treatment of IUGR fetuses.

Hungarian indigenous Tsigai, a promising breed for excellent heat tolerance and immunity

The adverse effects of climate change on sheep farming have become more noticeable in recent decades. Extensive efforts have been made to untangle the complex relationship between heat tolerance, animal health, and productivity, also to identify a resilient and economically suitable breed for selection that can be resilient to future climate change conditions. Using quantitative real-time polymerase chain reaction (qRT-PCR), we observed the seasonal variations in the expression of several important genes related to heat stress and immunity (HSP70, IL10, TLR2, TLR4, and TLR8) in three of the most widely kept sheep breeds in Hungary: The indigenous Tsigai, Hungarian Merino, and White Dorper. We found that the seasonal stressor affected the relative gene expression of all genes in this study. Notably, The Hungarian indigenous Tsigai was the most robust breed adapted to the Hungarian continental (hot summer, cold winter) environment, with excellent thermotolerance and immunity. Furthermore, despite suffering from heat stress in the summer, Hungarian Merino maintained their robust immune system well throughout the year.

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.

Blood Transcriptomic Analyses Reveal Functional Pathways Associated with Thermotolerance in Pregnant Ewes Exposed to Environmental Heat Stress

Environmental heat stress triggers a series of compensatory mechanisms in sheep that are dependent on their genetic regulation of thermotolerance. Our objective was to identify genes and regulatory pathways associated with thermotolerance in ewes exposed to heat stress. We performed next-generation RNA sequencing on blood collected from 16 pregnant ewes, which were grouped as tolerant and non-tolerant to heat stress according to a physiological indicator. Additional samples were collected to measure complete blood count. A total of 358 differentially expressed genes were identified after applying selection criteria. Gene expression analysis detected 46 GO terms and 52 KEGG functional pathways. The top-three signaling pathways were p53, RIG-I-like receptor and FoxO, which suggested gene participation in biological processes such as apoptosis, cell signaling and immune response to external stressors. Network analysis revealed ATM, ISG15, IRF7, MDM4, DHX58 and TGFβR1 as over-expressed genes with high regulatory potential. A co-expression network involving the immune-related genes ISG15, IRF7 and DXH58 was detected in lymphocytes and monocytes, which was consistent with hematological findings. In conclusion, transcriptomic analysis revealed a non-viral immune mechanism involving apoptosis, which is induced by external stressors and appears to play an important role in the molecular regulation of heat stress tolerance in ewes.

Heat Stress as a Barrier to Successful Reproduction and Potential Alleviation Strategies in Cattle

In recent decades, the adverse effects of global warming on all living beings have been unanimously recognized across the world. A high environmental temperature that increases the respiration and rectal temperature of cattle is called heat stress (HS), and it can affect both male and female reproductive functions. For successful reproduction and fertilization, mature and healthy oocytes are crucial; however, HS reduces the developmental competence of oocytes, which compromises reproduction. HS disturbs the hormonal balance that plays a crucial role in successful reproduction, particularly in reducing the luteinizing hormone and progesterone levels, which leads to severe problems such as poor follicle development with a poor-quality oocyte and problems related to maturity, silent estrus, abnormal or weak embryo development, and pregnancy loss, resulting in a declining reproduction rate and losses for the cattle industry. Lactating cattle are particularly susceptible to HS and, hence, their reproduction rate is substantially reduced. Additionally, bulls are also affected by HS; during summer, semen quality and sperm motility decline, leading to compromised reproduction. In summer, the conception rate is reduced by 20-30% worldwide. Although various techniques, such as the provision of water sprinklers, shade, and air conditioning, are used during summer, these methods are insufficient to recover the normal reproduction rate and, therefore, special attention is needed to improve reproductive efficiency and minimize the detrimental effect of HS on cattle during summer. The application of advanced reproductive technologies such as the production of embryos in vitro, cryopreservation during the hot season, embryo transfer, and timed artificial insemination may minimize the detrimental effects of HS on livestock reproduction and recover the losses in the cattle industry.

Supplementation of Moringa oleifera leaf concentrate pellets on nutrient utilization, antioxidant status, and reproductive performance of prolific ewes during extreme summer months in semi-arid tropical conditions

A feeding trial was conducted for a period of 60 days during extreme summer months to observe the effect of supplementation of Moringa oleifera leaves containing concentrate pellets on nutrient utilization, antioxidant status, and reproductive performance in Avishaan ewes reared under semi-arid condition. Forty adult non-pregnant cyclic ewes (2-3 years, 31.8 ± 0.81 kg body weight) were selected and randomly allocated into 2 groups of 20 animals each, viz., G-I (control) and G-II (treatment). The ewes were grazed on natural pasture for 8 h, offered ad libitum Cenchrus ciliaris hay after grazing and concentrate pellets @ 300 g/animal/day. The ewes in G-I were offered conventional concentrate pellets, whereas G-II ewes were offered concentrate pellets containing 15% Moringa leaves. The mean temperature humidity index during the period of study was 27.5 ± 0.3 and 34.6 ± 0.4 at 0700 h and 1400 h, respectively, indicating severe heat stress. Nutrient intake and utilization were comparable between the two groups. The antioxidant status was higher in G-II ewes as the values of catalase, superoxide dismutase, and total antioxidant capacity were higher (P < 0.05) in G-II ewes compared to G-I. The conception rate was higher (100%) in G-II ewes than G-I ewes (70%). Multiple birth percentage was 77.8% in G-II ewes, and it was comparable with the herd average of Avishaan (74.7%). However, ewes in G-I group exhibited a marked decline in multiple birth percentage (28.6%) than the normal herd average. Hence, it can be concluded that inclusion of Moringa oleifera leaves in feeding of prolific Avishaan ewes improved their antioxidant status resulting in optimum reproductive performance during stressful summer months.