Heat stress impact on the expression patterns of different reproduction related genes in Malabari goats

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.

Alterations in the uterine echotexture, hemodynamics, and histological findings in relation to metabolomic profiles in goats with different ovarian activities (active versus inactive ovaries)

This study investigated, for the first time, the alterations in the uterine echotexture and blood flow in cyclic and acyclic (inactive ovary) goats using ultrasonography. The study aimed also to evaluate the metabolomic changes in the plasma of cyclic and acyclic goats. Furthermore, the histopathological approach was applied to the specimens of the uterus to validate the findings of this study. Based on monitoring the estrous cyclicity, goats were assigned into either a cyclic group or an acyclic one (n = 7, each). Ovarian morphometry and hemodynamics were assessed to confirm group assignment. Full ultrasonographic examinations were performed to assess the uterine echotexture by B-mode ultrasonography and uterine hemodynamics by color Doppler ultrasonography in the cyclic group (at days 10-12) and acyclic group. Additionally, blood samples were withdrawn for measuring hormonal concentrations and for metabolomics analysis. Specimens of the uterus were executed for histopathological evaluation in both groups. Results revealed alterations in the uterine hemodynamics and endometrial echotexture. Goats in the cyclic group attained a significantly higher color pixel area of the endometrium compared to those in the acyclic one (P< 0.001). However, the pixel intensity of the endometrium echotexture was significantly (P< 0.05) lower in the cyclic group than in the smooth inactive ovary one. There were significant (P< 0.05) increases in the concentrations of FSH, LH, and inhibin in the cyclic group compared to their concentrations in the acyclic one. Goats in the acyclic group attained noticeable (P< 0.001) lower concentrations of E2 and P4 than in the cyclic goats. The metabolomic results revealed the existence of several up- and down-regulated metabolites among the studied groups. In this investigation, untargeted metabolomic analysis revealed the existence of 5 up-regulated metabolites (ketoleucine, L-fucose, D-glucurono-6,3-lactone, melatonin, and 5-methoxy tryptamine) and 5 down-regulated ones (p-octopamine, 3-hydroxyisovaleric acid, methylmalonic acid, 4-hydroxyphenylpyruvic acid, and cadaverine) in the cyclic group compared to the acyclic one. The enrichment analysis of the significant metabolites showed top pathways that may be involved in these changes, such as fructose and mannose metabolism, valine. Leucine, and isoleucine biosynthesis, linoleic acid metabolism, arginine biosynthesis, and vitamin B6 metabolism based on the KEGG enriched pathway. Altogether, the histopathological assessment showed noticeable changes in the columnar epithelial lining of the endometrial epithelium, endometrial vascularity, and endometrial glands among the studied groups. In conclusion, this study extrapolated the differences between cyclic goats (during the mid-luteal phase) and acyclic ones in terms of hormonal, hemodynamics, echotexture of the uterus, and circulating metabolomics. These findings are very crucial to fully assess the fertility potential in goats.

Scientific knowledge about gene expression in ruminants under heat stress - A scientometric review

Heat stress can alter the expression of genes in the individual's molecular response. The identification of these genes makes it possible to better understand the molecular response, identifying biomarker genes and indirect response pathways that can help with genetic improvement studies, animal welfare, separating more thermotolerant varieties and mitigating the effects of heat stress. The aim of this scientometric review was to characterize the state of the art of scientific research into gene expression in ruminants under heat stress, to define the most studied species, biology systems and genes, as well as the related biological pathways and processes. The articles for the dataset were compiled in the Web of Science database, refined individually and analyzed using the CiteSpace, RStudio, Excel and GraphPad Prism programs and the KEGG (Kyoto Encyclopedia of Genes and Genomes) database. The publications formed a data set containing 271 articles and an H-index of 37. The number of publications increased from 2011. The countries with the highest frequency of publications are India, the United States, China and Brazil, the ruminant species are cattle, buffaloes, sheep and goats, all zootechnical interest, and biology systems was reproduction, blood and lactation, due to the economic importance of the quality and quantity of production, to the ease of collecting and possibility of studies in vitro. Cattle have been extensively studied in comparison to other ruminants. The HSP70 gene has been the most studied, followed by the HSP family, HSF, BAX, TLR and BCL-2, these genes can be molecular markers of heat stress. The main pathways and biological processes of genes were in cattle the cancer pathway; in goats the Mixed, incl. myd88-dependent toll-like receptor signaling pathway, and lipopolys; in sheep the oxidoreductase; and in buffalo it was the BCL-2 family. The molecular responses are still recent and have not been established.

Advances in the Effects of Heat Stress on Ovarian Granulosa Cells: Unveiling Novel Ferroptosis Pathways

Heat stress has been one of the key research areas for researchers due to the wide-ranging effects and complex mechanisms of action of its stress product reactive oxygen species (ROS). The aim of this paper is to comprehensively review and summarize the effects of heat stress on ovarian granulosa cells and their mechanism of action. We systematically reviewed the effects of heat stress on ovarian granulosa cells, including intracellular steroid hormone changes, oxidative stress, apoptosis, and mitochondrial function. Meanwhile, this paper discusses in detail several major mechanisms by which heat stress induces apoptosis in ovarian granulosa cells, such as through the activation of apoptosis-related genes, induction of endoplasmic reticulum stress, and the mitochondrial pathway. In addition, we analyzed the mechanism of ferroptosis in ovarian granulosa cells under heat stress conditions, summarized the potential association between heat stress and ferroptosis in light of the existing literature, and explored the key factors in the mechanism of action of heat stress, such as the signaling pathways of Nrf2/Keap1, HSPs, and JNK, and analyzed their possible roles in the process of ferroptosis. Finally, this paper provides an outlook on the future research direction, describing the possible interaction between heat stress and ferroptosis, with a view to providing a theoretical basis for further understanding and revealing the complex mechanism of ferroptosis occurrence in ovarian granulosa cells under heat stress.

Effect of heat stress on blood biochemistry and energy metabolite of the Dazu black goats

The objective of this study was to determine the effects of heat stress (HS) on physiological, blood biochemical, and energy metabolism in Dazu black goats. Six wether adult Dazu black goats were subjected to 3 experimental periods: high HS (group H, temperature-humidity index [THI] > 88) for 15 d, moderate HS (group M, THI was 79-88) for 15 d, and no HS (group L, THI < 72) for 15 d. Rectal temperature (RT) and respiratory rate (RR) were determined on d 7 and 15 of each period, and blood samples were collected on d 15 of each period. All goats received glucose (GLU) tolerance test (GTT) and insulin (INS) tolerance test on d 7 and d 10 of each period. The results showed that HS decreased dry matter intake (DMI) and INS concentration (p < 0.05), and increased RT, RR, non-esterified fatty acid (NEFA), cortisol (COR), and total protein (TP) concentrations (p < 0.05). Compared to group L, the urea nitrogen (BUN) concentration increased and GLU concentration decreased in group H (p < 0.05). During the GTT, the area under the curve (AUC) of GLU concentrations increased by 12.26% (p > 0.05) and 40.78% (p < 0.05), and AUC of INS concentrations decreased by 26.04 and 14.41% (p < 0.05) in groups H and M compared to group L, respectively. The INS concentrations were not significant among the three groups (p > 0.05) during the ITT. A total of 60 differentially expressed metabolites were identified in response to groups H and M. In HS, changes in metabolites related to carbohydrate metabolism and glycolysis were identified (p < 0.05). The metabolites related to fatty acid β-oxidation accumulated, glycogenic and ketogenic amino acids were significantly increased, while glycerophospholipid metabolites were decreased in HS (p < 0.05). HS significantly increased 1-methylhistidine, creatinine, betaine, taurine, taurolithocholic acid, inosine, and hypoxanthine, while decreasing vitamin E in blood metabolites (p < 0.05). In summary, HS changed the metabolism of fat, protein, and energy, impaired GLU tolerance, and mainly increased amino acid metabolism to provide energy in Dazu black goats.

Heat Stress and Goat Welfare: Adaptation and Production Considerations

This review attempted to collate and synthesize information on goat welfare and production constraints during heat stress exposure. Among the farm animals, goats arguably are considered the best-suited animals to survive in tropical climates. Heat stress was found to negatively influence growth, milk and meat production and compromised the immune response, thereby significantly reducing goats' welfare under extensive conditions and transportation. Although considered extremely adapted to tropical climates, their production can be compromised to cope with heat stress. Therefore, information on goat adaptation and production performance during heat exposure could help assess their welfare. Such information would be valuable as the farming communities are often struggling in their efforts to assess animal welfare, especially in tropical regions. Broadly three aspects must be considered to ensure appropriate welfare in goats, and these include (i) housing and environment; (ii) breeding and genetics and (iii) handling and transport. Apart from these, there are a few other negative welfare factors in goat rearing, which differ across the production system being followed. Such negative practices are predominant in extensive systems and include nutritional stress, limited supply of good quality water, climatic extremes, parasitic infestation and lameness, culminating in low production, reproduction and high mortality rates. Broadly two types of methodologies are available to assess welfare in goats in these systems: (i) animal-based measures include behavioral measurements, health and production records and disease symptoms; (ii) resources based and management-based measures include stocking density, manpower, housing conditions and health plans. Goat welfare could be assessed based on several indicators covering behavioral, physical, physiological and productive responses. The important indicators of goat welfare include agonistic behavior, vocalization, skin temperature, body condition score (BCS), hair coat conditions, rectal temperature, respiration rate, heart rate, sweating, reduced growth, reduced milk production and reduced reproductive efficiency. There are also different approaches available by which the welfare of goats could be assessed, such as naturalistic, functional and subjective approaches. Thus, assessing welfare in goats at every production stage is a prerequisite for ensuring appropriate production in this all-important species to guarantee optimum returns to the marginal and subsistence farmers.

Comparative Assessment of Thermotolerance in Dorper and Second-Cross (Poll Dorset/Merino × Border Leicester) Lambs

Simple Summary

Selection of animal breeds that are adapted to extreme climatic conditions may help to sustain livestock production in the face of climate change. We measured the thermotolerance of 4–5-month-old Dorper and second-cross lambs (Poll Dorset × (Border Leicester × Merino)) by assessing feed intake, physiological, blood biochemical and prolactin responses. Heat stress reduced feed intake only in second-cross lambs but not in Dorpers. As expected, heat stress also increased water intake, respiration rate, rectal temperature, and skin temperature in both genotypes, but to a lesser extent in Dorpers. The comparatively lower influence of heat stress on thermotolerance indices in Dorper indicates adaptability of this breed to heat challenge.

Abstract

The objective of this study was to compare the thermotolerance of second-cross (SC; Poll Dorset × Merino × Border Leicester) and Dorper lambs. Dorper and SC lambs (4–5 months of age) were subjected to cyclic heat stress (HS) (28–40 °C). The temperature was increased to 38–40 °C between 800 and 1700 h daily and maintained at 28 °C for the remainder of the day (30–60% relative humidity (RH)) in climatic chambers for 2 weeks (n = 12/group), with controls maintained in a thermoneutral (TN) (18–21 °C, 40–50% RH) environment (n = 12/group). Basal respiration rate (RR), rectal temperature (RT) and skin temperature (ST) were higher (p < 0.01) in SC lambs than in Dorpers. HS increased RR, RT and ST (p < 0.01) in both genotypes, but the levels reached during HS were lower (p < 0.01) in Dorpers. HS increased (p < 0.01) water intake to a greater extent in SC lambs, while feed intake was reduced (p < 0.05) by HS in SC lambs but not in Dorpers. HS increased (p < 0.01) blood urea nitrogen and creatinine in SC lambs only. Plasma non-esterified fatty acid concentrations were reduced (p < 0.05) by HS in SC lambs but increased (p < 0.05) in Dorpers. There was no effect of HS on pO₂, cHCO₃⁻ and cSO₂, but higher (p < 0.01) blood pH and lower (p < 0.01) pCO₂ were recorded under HS in both genotypes. Blood electrolytes and base excess were reduced (p < 0.01) under HS, while a genotype difference (p < 0.05) was only observed in blood K⁺ and hemoglobin concentrations. Basal plasma prolactin concentrations were lower (p < 0.01) in Dorpers but were elevated at a similar level during HS (p < 0.01) in both genotypes. Dorper lambs are more resilient to HS than SC lambs. Future research should focus on confirming whether the better heat tolerance of Dorpers is translated to better returns in terms of growth performance and carcass traits over the summer months.