The impact of heat stress on the immune system in dairy cattle: A review

Effects of Saccharomyces Cerevisiae Cultures on Performance and Immune Performance of Dairy Cows During Heat Stress

The dairy farming industry is facing massive economic losses as heat stress continues to rise. The purpose of this study was to see how feeding Saccharomyces cerevisiae culture (SC) influences productive performance, lactation performance, serum biochemical indexes, hormonal level, antioxidant capacity, and immune function in mid-lactating cows during heat stress. Forty-five healthy mid-lactation dairy cows with comparable milk yield, lactation days, and parity were randomly divided into 3 groups (15 cows in each group). The control group (CON) was fed the basal diet, while the treatment groups were fed the basal diet + first Saccharomyces cerevisiae culture 100 g/d (SC-1) and the basal diet + second Saccharomyces cerevisiae culture 30 g/d (SC-2), respectively. The SC-1 and SC-2 groups with SC added in the treatment groups reduced rectal temperature and respiratory rate in heat-stressed cows (P < 0.05). The milk yield of SC-1 and SC-2 treatment groups was significantly higher than that of CON (P < 0.05). Except for somatic cell count, which was significantly lower in SC-1 and SC-2 than in CON (P < 0.05), there were no significant differences in the milk components. The addition of SC: (i) increased serum urea levels (P < 0.05), but there was no significant difference in glucose, total cholesterol, alanine transaminase, aspartate aminotransferase, total protein, albumin and alkaline phosphatase levels (P > 0.05); (ii) increased serum levels of immunoglobulin-A, immunoglobulin-G, immunoglobulin M, interleukin-4, interleukin-10 and heat shock protein-70 (P < 0.05), while decreasing serum levels of interleukin-1β, interleukin-6, interleukin-2, interferon-γ and tumor necrosis factor-α (P < 0.05); (iii) increased total antioxidant capacity, glutathione peroxidase and superoxide dismutase in serum (P < 0.05), while decreasing malondialdehyde; (iv) increased serum levels of glucocorticoids, insulin, cortisol and prolactin (P < 0.05), while decreasing the serum levels of triiodothyronine and thyroxine (P < 0.05). In conclusion, under the current experimental conditions, the addition of SC can reduce rectal temperature and respiratory rate in heat-stressed mid-lactation cows, reduce the number of somatic cells in milk and improve the mid-lactation cow performance. In addition, SC addition to the diet can raise serum urea levels, regulate serum hormone levels, boost antioxidant capacity in mid-lactation cows, and boost overall immunity.

Heat Stress: Effects on Rumen Microbes and Host Physiology, and Strategies to Alleviate the Negative Impacts on Lactating Dairy Cows

Heat stress (HS) in dairy cows causes considerable losses in the dairy industry worldwide due to reduced animal performance, increased cases of metabolic disorders, altered rumen microbiome, and other health problems. Cows subjected to HS showed decreased ruminal pH and acetate concentration and an increased concentration of ruminal lactate. Heat-stressed cows have an increased abundance of lactate-producing bacteria such as Streptococcus and unclassified Enterobacteriaceae, and soluble carbohydrate utilizers such as Ruminobacter, Treponema, and unclassified Bacteroidaceae. Cellulolytic bacteria, especially Fibrobacteres, increase during HS due to a high heat resistance. Actinobacteria and Acetobacter, both acetate-producing bacteria, decreased under HS conditions. Rumen fermentation functions, blood parameters, and metabolites are also affected by the physiological responses of the animal during HS. Isoleucine, methionine, myo-inositol, lactate, tryptophan, tyrosine, 1,5-anhydro-D-sorbitol, 3-phenylpropionic acid, urea, and valine decreased under these conditions. These responses affect feed consumption and production efficiency in milk yield, growth rate, and reproduction. At the cellular level, activation of heat shock transcription factor (HSF) (located throughout the nucleus and the cytoplasm) and increased expression of heat shock proteins (HSPs) are the usual responses to cope with homeostasis. HSP70 is the most abundant HSP family responsible for the environmental stress response, while HSF1 is essential for increasing cell temperature. The expression of bovine lymphocyte antigen and histocompatibility complex class II (DRB3) is downregulated during HS, while HSP90 beta I and HSP70 1A are upregulated. HS increases the expression of the cytosolic arginine sensor for mTORC1 subunits 1 and 2, phosphorylation of mammalian target of rapamycin and decreases the phosphorylation of Janus kinase-2 (a signal transducer and activator of transcription factor-5). These changes in physiology, metabolism, and microbiomes in heat-stressed dairy cows require urgent alleviation strategies. Establishing control measures to combat HS can be facilitated by elucidating mechanisms, including proper HS assessment, access to cooling facilities, special feeding and care, efficient water systems, and supplementation with vitamins, minerals, plant extracts, and probiotics. Understanding the relationship between HS and the rumen microbiome could contribute to the development of manipulation strategies to alleviate the influence of HS. This review comprehensively elaborates on the impact of HS in dairy cows and introduces different alleviation strategies to minimize HS.

Effect of a synbiotic supplement as an antibiotic alternative on broiler skeletal, physiological, and oxidative parameters under heat stress

The aim of this study was to examine if synbiotics can function as alternatives to antibiotics in broiler production under heat stress (HS). Day-old broiler chicks (528 birds) were randomly placed in floor pens within 2 identical temperature-controlled rooms (11 birds/pen and 24 pens/room). The pens of each room were evenly divided among 3 treatments (n = 8): basal diet (CON), the basal diet mixed with 50 ppm of bacitracin methylene disalicylate (BMD) or a synbiotic (50 ppm of PoultryStar me^US, SYN). From d 15, room 2 was under thermoneutral (TN) conditions (TN-CON, TN-BMD, and TN-SYN), while HS was applied to room 1 at 32^oC for 9 hrs/d (0800 to 1700) (HS-CON, HS-BMD, and HS-SYN). Treatment effects on footpad dermatitis and gait score were measured on 5 birds/pen, and latency to lie (LTL) test was measured on 2 birds/pen at d 27 and d 41; and 1 broiler/pen was sampled on d 28 and d 42, respectively. Body, liver, and spleen weight were determined. Plasma levels of interleukins (IL), heat shock protein 70, immunoglobulin (Ig)Y, liver superoxide dismutase (SOD) and glutathione peroxidase (GPx) enzyme activities were examined. Heat stress suppressed BW and IgY concentrations on both d 28 and d 42, while suppressed plasma IL-6 concentrations, SOD activities, and LTL duration on d 28 only (P < 0.05). Among all treatments, SYN birds had the best foot and skeletal health scores on both d 27 and d 41 (P < 0.05). On d 42, SYN increased BW, and TN-SYN birds had higher relative spleen weight than both TN-BMD and TN-CON birds (P < 0.05). Antibiotic BMD increased BW (P < 0.05) but decreased SOD activities (P < 0.05) on d 42. These results indicate that the SYN supplementation decreases HS negative effect on broilers by improving BW, foot, and skeletal health, while BMD improves BW but also increases oxidative stress in broilers. The data suggest that synbiotic supplement may function as an alternative to antibiotics in broiler production during summer seasons, especially in the tropical and subtropical regions.

Meta-Analysis and Systematic Review of the Thermal Stress Response: Gallus gallus domesticus Show Low Immune Responses During Heat Stress

Heat stress, which affects broiler growth performance and immunity, is a major concern in the poultry industry. This meta-analysis aimed to demonstrate the significant effect of heat stress on broiler mass gain and immunoglobulin levels, which regulates the mortality rate of broilers. A total of 2,585 studies were downloaded from PubMed, Web of Science, and Google Scholar from January 1, 2015, to September 1, 2021. Eventually, 28 studies were selected based on specific criteria. The results for body mass gain, total mass of immune organs (thymus, spleen, and bursa of Fabricius), immunoglobulin (IgA, IgG, and IgM) levels, and mortality rate were analyzed using odds ratio or the random-effects model (REM) at a confidence interval (CI) of 95%. Compared to the control, heat stress significantly decreased body mass gain (10 trials: REM = 1.35, 95% CI: 1.21, 1.50). Compared to that in the control, heat stress significantly increased immunoglobulin levels: IgA (7 trials: REM = 1.69, 95% CI: 0.90, 3.16), IgG (6 trials: REM = 1.24, 95% CI: 0.85, 1.81), IgM (8 trials: REM = 0.69, 95% CI: 0.44, 1.08), and heat stress also increased the broiler mortality rate (6 trials: REM = 0.06, 95% CI: 0.01, 0.27). However, there were no significant changes in the immune organs between the control and heat-stressed groups. In conclusion, heat stress remarkably alters the mass gain and immunoglobulin levels of broilers, which may be a cause of the high mortality rate.

A novel missense mutation (rs464874590) within BoLA-DOB gene associated with the heat-resistance in Chinese cattle

Bovine leukocyte antigen, class II, DO beta (BoLA-DOB) is related to antigen presentation, which can triggered by multicul factors. And the condition of immune function determines how much cattle load to heat stress. To evaluate the relationship between heat-resistance and single nucleotide polymorphisms (SNPs) in BoLA-DOB gene, our study has taken further analysis in Chinese indigenous cattle for the first time. A missense single nucleotide polymorphism (rs464874590) was detected in BoLA-DOB gene. We directly sequenced rs464874590 (NM_001013600.1 g.7122762 A > G) in BoLA-DOB gene of 522 individuals of 26 cattle breeds. The frequency of allele G gradually decreases from south to north with distinct climatic distribution characteristics. Further association analysis was carried out between different genotypes and environmental parameters, including annual mean temperature (T), relative humidity (RH), and temperature-humidity index (THI). The result showed that three genotypes were significantly correlated with T, H, and THI (P < 0.01), indicating that GG genotype was distributed in areas with hot and moist conditions. Therefore, our results suggested that the rs464874590 could be applied as a genetic marker to detect the heat-resistance of Chinese indigenous cattle.

Climate Change and Livestock Production: A Literature Review

Globally, the climate is changing, and this has implications for livestock. Climate affects livestock growth rates, milk and egg production, reproductive performance, morbidity, and mortality, along with feed supply. Simultaneously, livestock is a climate change driver, generating 14.5% of total anthropogenic Greenhouse Gas (GHG) emissions. Herein, we review the literature addressing climate change and livestock, covering impacts, emissions, adaptation possibilities, and mitigation strategies. While the existing literature principally focuses on ruminants, we extended the scope to include non-ruminants. We found that livestock are affected by climate change and do enhance climate change through emissions but that there are adaptation and mitigation actions that can limit the effects of climate change. We also suggest some research directions and especially find the need for work in developing country settings. In the context of climate change, adaptation measures are pivotal to sustaining the growing demand for livestock products, but often their relevance depends on local conditions. Furthermore, mitigation is key to limiting the future extent of climate change and there are a number of possible strategies.

Benefits of Veterinary Herd Health Management on German Dairy Farms: Status Quo and Farmers' Perspective

Veterinary Herd Health Management plays an important role in veterinary medicine on dairy farms and has also been mandatory at the European Union level since April 21, 2021. Despite the increasing importance of VHHM, little is known about the extent of utilization of VHHM by dairy farmers and their view on this type of collaboration. Therefore, this cross-sectional study aimed to determine the status quo of the currently practiced VHHM in Germany. For this purpose, an online survey was conducted among dairy farmers in November and December 2020. From 216 analyzed questionnaires, about half (n = 106) of the surveyed dairy farmers used VHHM at different scopes. However, regardless of the group, the term “veterinary herd health management” generally was given most relative importance by the participants as a veterinary service for herd fertility improvement, rather than the actual definition of a holistic approach. In contrast to this, the actual motivation of the VHHM participants, to take part in such a program was primarily based on the desire to safeguard animal health by employing preventive measures, that is, to avoid the occurrence of diseases via improved management and to improve farm performance (and profitability). Dairy farmers who opted for VHHM tended to manage larger higher yielding herds than those who did not. Additionally, the farmers in latter farms were more likely to make joint animal health decisions with their veterinarians. Using a latent class analysis, two groups of farmers among farms that were not currently using VHHM were identified, one of which expressed great interest in using VHHM while the other did not. Since the new legal basis makes the topic even more relevant than before, dairy farmers, animals, and veterinarians might benefit from the study to exploit hidden opportunities for VHHM collaboration.

Effect of 6‐n‐propyl‐2‐thiouracil or dexamethasone administration on the responses of antimicrobial components in goat milk to intramammary lipopolysaccharide infusion

Heat stress impacts the immune system of dairy animals by altering the hypothalamic-pituitary-adrenal axis and thyroid function, leading to conditions such as hypothyroidism and hypercortisolism. This study aimed to elucidate the effect of hypothyroidism and hypercortisolism on the response of mammary innate immune function to inflammation caused by Escherichia coli in dairy goats. To induce hypothyroidism and hypercortisolism, we administered 6-n-propyl-2-thiouracil (PTU; for 21 days) and dexamethasone (DEX; for 5 days), respectively, to six goats each; six goats without treatment were used as the control group. After treatment, lipopolysaccharide (LPS) from E. coli O111 was infused into the mammary gland. Somatic cell counts (SCC) and levels of lactoferrin (LF), S100A7, immunoglobulin A (IgA), and interleukin-8 (IL-8) in milk until 7 days after LPS infusion were measured. An increase in SCC after LPS infusion was inhibited in both PTU and DEX groups, and an increase in LF after LPS infusion was inhibited in PTU group, compared with that in the control group. The results of the present study suggest that the recruitment of neutrophils and LF production decreased under hypothyroidism or hypercortisolism, which may be one of the causes underlying increased incidence of mastitis in dairy animals under heat stress conditions.

Inflammatory Mediation of Heat Stress-Induced Growth Deficits in Livestock and Its Potential Role as a Target for Nutritional Interventions: A Review

Simple Summary

Heat stress is a persistent challenge for livestock producers. Molecular changes throughout the body that result from sustained heat stress slow muscle growth and thus are detrimental to carcass yield and value. Feedlot animals are at particularly high risk for heat stress because their confinement limits their ability to pursue shade and other natural cooling behaviors. Changes in infrastructure to reduce the impact of heat stress are often cost-prohibitive, but recent studies have revealed that anti-inflammatory therapies may help to improve growth deficits in heat-stressed animals. This review describes the conditions that cause heat stress and explains the role of inflammation in muscle growth impairment. Additionally, it discusses the potential for several natural anti-inflammatory dietary additives to improve muscle growth outcomes in heat-stressed livestock.

Abstract

Heat stress is detrimental to well-being and growth performance in livestock, and systemic inflammation arising during chronic heat stress contributes to these poor outcomes. Sustained exposure of muscle and other tissues to inflammation can impair the cellular processes that facilitate muscle growth and intramuscular fat deposition, thus reducing carcass quality and yield. Climate change is expected to produce more frequent extreme heat events, increasing the potential impact of heat stress on sustainable livestock production. Feedlot animals are at particularly high risk for heat stress, as confinement limits their ability to seek cooling from the shade, water, or breeze. Economically practical options to circumvent heat stress in feedlot animals are limited, but understanding the mechanistic role of inflammation in heat stress outcomes may provide the basis for treatment strategies to improve well-being and performance. Feedlot animals receive formulated diets daily, which provides an opportunity to administer oral nutraceuticals and other bioactive products to mitigate heat stress-induced inflammation. In this review, we examine the complex associations between heat stress, systemic inflammation, and dysregulated muscle growth in meat animals. We also present evidence for potential nutraceutical and dietary moderators of inflammation and how they might improve the unique pathophysiology of heat stress.

Effects of Compost-Bedded Pack Barn on Circulating Cortisol and Beta-Endorphins in Dairy Cows: A Case Study

Simple Summary

Management and housing conditions have been reported to significantly affect the health and welfare of livestock species. Therefore, the adoption of novel, alternative housing systems (such as the compost-bedded pack barn, developed in the USA) requires extensive research to assess the implications for animal welfare. From a general point of view, animal welfare is typically assessed by means of animal-based (such as blood biochemical markers) and resource-based (such as management practices) indicators. Based on such considerations, the present study evaluated the fluctuation of circulating cortisol and beta-endorphins in dairy cows housed in a conventional freestall barn (FB) and in the alternative compost-bedded pack barn (CB). The results obtained suggest that the CB housing system did not elicit significant changes in either blood cortisol or beta-endorphins.

Abstract

The up-to-date literature suggests that the compost-bedded pack barn housing system is capable of remarkably improving productive and reproductive performance, as well as health status and welfare, in dairy cattle. However, there is currently limited knowledge available on the endocrine and biochemical changes in animals housed in such alternative systems. Therefore, this study aimed to measure blood cortisol (COR) and beta-endorphins (BE) in 22 two-year-old primiparae Fleckvieh cows, who were randomly allotted to the following two different housing systems: CB (n = 11) and FB (n = 11). Blood samples were collected at the beginning of the experiment (T0) and every two months thereafter (T1, T2, and T3). The COR and BE were measured through an immunoenzymatic kit. With the only exception being T0, no differences were observed over time between the two groups, neither for COR nor for BE. However, the blood cortisol levels of the CB cows decreased over time, while a T1 peak was identified in the FB group. On the contrary, both the housing systems displayed numerically higher BE at T3 than at the other experimental times. Therefore, the overall data suggest that the compost-bedded pack barn did not significantly affect the studied parameters. Accordingly, cow welfare should be assessed using a wider panel of animal-based indicators.

Perches as Cooling Devices for Reducing Heat Stress in Caged Laying Hens: A Review

Heat stress is one of the most detrimental environmental challenges affecting the biological process and the related production performance of farm animals, especially in poultry. Commercial laying hens have been bred (selected) for high egg production, resulting in increased sensitivity to heat stress due to breeding-linked metabolic heat production. In addition, laying hens are prone to heat stress due to their inadequate species-specific cooling mechanisms resulting in low heat tolerance. In addition, hens have no sweat glands and feathering covers almost their entire body to minimize body heat loss. The poultry industry and scientists are developing cooling methods to prevent or reduce heat stress-caused damage to chicken health, welfare, and economic losses. We have designed and tested a cooling system using perches, in which chilled water (10 °C) circulates through a conventional perch passing through the layer cages to offer the cooling potential to improve hen health, welfare, and performance during acute and chronic periods of heat stress (35 °C). This review summarizes the outcomes of a multi-year study using the designed cooled perch system. The results indicate that conducting heat from perching hens directly onto the cooled perch system efficiently reduces heat stress and related damage in laying hens. It provides a novel strategy: perches, one key furnishment in cage-free and enriched colony facilities, could be modified as cooling devices to improve thermal comfort for hens during hot seasons, especially in the tropical and subtropical regions.

Review: Future consequences of climate change for European Union pig production

Climate change is already a reality for livestock production. In contrast to the ruminant species, little is known about the impacts and the vulnerability of pig European Union (EU) sector to climate warming. This review deals with the potential and the already measurable effects of climate change in pig production. Based on evidences published in the literature, climate change may reduce EU pig productivity by indirectly reducing the availability of crops usually used in pig feeding, spreading the vector or pathogen to new locations and increasing the risk of exposure to cereals contaminated with mycotoxins; and directly mainly by inducing heat stress and increasing the animal's susceptibility to various diseases. Provision of realistic projections of possible impacts of future climate changes on EU pig sector is a prerequisite to evaluate its vulnerability and propose effective adaptation strategies. Simulation modelling approach is the most commonly used approach for exploring the effects of medium or long-term climate change/variability in pig production. One of the main challenges for this modelling approach is to account for both direct and indirect possible effects but also to uncertainties in parameter values that substantially increase the uncertainty estimates for model projections. The last part of the paper focus on the main issues that still need to be overcome for developing a decision support tools for simulating the direct and indirect effect of climate change in pig farms.

Effect of chitosan on blood profile, inflammatory cytokines by activating TLR4/NF-κB signaling pathway in intestine of heat stressed mice

Heat stress can significantly affect the immune function of the animal body. Heat stress stimulates oxidative stress in intestinal tissue and suppresses the immune responses of mice. The protecting effects of chitosan on heat stress induced colitis have not been reported. Therefore, the aim of this study was to investigate the protective effects of chitosan on immune function in heat stressed mice. Mice were exposed to heat stress (40 °C per day for 4 h) for 14 consecutive days. The mice (C57BL/6J), were randomly divided into three groups including: control group, heat stress, Chitosan group (LD: group 300 mg/kg/day, MD: 600 mg/kg/day, HD: 1000 mg/kg/day). The results showed that tissue histology was improved in chitosan groups than heat stress group. The current study showed that the mice with oral administration of chitosan groups had improved body performance as compared with the heat stress group. The results also showed that in chitosan treated groups the production of HSP70, TLR4, p65, TNF-α, and IL-10 was suppressed on day 1, 7, and 14 as compared to the heat stress group. In addition Claudin-2, and Occludin mRNA levels were upregulated in mice receiving chitosan on day 1, 7, and 14 of heat stress. Furthermore, the IL-6, IL-10, and TNF-α plasma levels were down-regulated on day 1, 7, and 14 of heat stress in mice receiving the oral administration of chitosan. In conclusion, the results showed that chitosan has an anti-inflammatory ability to tolerate hot environmental conditions.

Effects of dietary supplementation with alpha-lipoic acid on apparent digestibility and serum metabolome alterations of sheep in summer

To investigate the effects of alpha-lipoic acid (LA) on the nutrition metabolism of sheep (36.72 ± 1.44 kg) in the summer, twenty-one sheep were randomly assigned to three treatments addressing LA supplementation: 0.00 (CTL), 600 (LA-L), and 900 (LA-H) mg/kg of dry matter (DM) per day for each sheep. Whole feces and urine collection methods were used to analyze apparent digestibility; ELISA kits to determine the hormones, antioxidant, and immune parameters in the blood; and serum metabolomics to detect and analyze small molecular substances. The results showed the DM intakes in the LA-L and LA-H groups were significantly increased by 8.22% and 8.02%, respectively, compared to that in the CTL group, and there was no significant effect on average daily gain, feed conversion ratio, nitrogen digestibility, calcium digestibility, and phosphorus digestibility. Regarding hormones, antioxidant, and immune indicators, the concentrations of triiodothyronine, superoxide dismutase, glutathione reductase, HSP70, and IgA significantly increased after LA supplementation, while adrenaline and malondialdehyde levels significantly decreased. With the pairwise comparison of the three groups, metabolomics analysis identified 22 differential metabolites in the positive/negative modes, respectively, which suggested LA supplementation can significantly affect sheep's lipid, amino acid, and nucleic acid metabolism. Additionally, 3-indolepropionic acid, cinnamoylglycine, butyric acid, dodecanedioic acid, indoxyl sulfate, and pantothenic acid were the common differential metabolites with higher concentrations after LA supplementation. In summary, dietary supplementation of LA can increase the sheep's DMI, energy digestibility, antioxidant capacity, and immunity. These changes provide evidence to support the use of LA supplementation for livestock.

Genetic and seasonal variations of Trypanosoma theileri and the association of Trypanosoma theileri infection with dairy cattle productivity in Northern Japan

Trypanosoma theileri is considered a non- or low-pathogenic trypanosome that generally causes latent infection in apparently healthy cattle; however, T. theileri propagates in the bloodstream and may cause clinical disease in pregnant animals or co-infection with bovine leukemia virus or Theileria orientalis. In the current study, a monthly survey of T. theileri infection over one year was carried out in a research dairy farm in Hokkaido, Japan to determine the 1) seasonal variations in the prevalence, 2) genetic characterization of T. theileri, and 3) associations of milk and blood parameters in dairy cattle with T. theileri infection, including data of metabolic profile tests and dairy herd performance tests, using linear mixed models. We found that 1) the prevalence of T. theileri infection was significantly higher in summer and winter than in other seasons; 2) T. theileri possibly showed genetic diversity in Eastern Hokkaido; and 3) T. theileri infection was associated with significantly lower levels of blood urea nitrogen, milk protein, and solids-not-fat, which are caused by a low rumen fermentation level. This is the first study to report the negative impact of T. theileri infection in dairy cattle, and our study indicates that control of T. theileri infection can improve the productivity of dairy cattle.

Terpinen4-ol inhibits heat stress induced inflammation in colonic tissue by Activating Occludin, Claudin-2 and TLR4/NF-κB signaling pathway

Heat stress has severe implications on the health of mice involving intestinal mucosal barrier damage and dysregulated mucosal immune response. This study was designed with long-term heat stress to detect the protective effect of terpinen4-ol on body weight, colon length, organ index, morphological structure, inflammatory cytokines expression, Claudin-2, Occludin, and TLR4 signaling pathway of colonic tissue in mice under heat stress. A study found that oral administration of terpinen4-ol helped against mortality and intestinal inflammation in a mouse model of acute colitis induced by heat stress (40 °C per day for 4 h) exposed for 14 consecutive days. The mice were divided into five groups including control, heat stress, terpinen4-ol low dose (TER LD: 5 mg/kg), medium dose (TER MD: 10 mg/kg), and high dose (TER HD: 20 mg/kg) group. Our study showed that the heat-stress terpinen4-ol group had improved body weight, colon length, and organ index, the number of white blood cells, lymphocytes, and neutrophils in the blood as compared to the heat stress group. In addition, results showed that heat stress upregulated the expression of TLR4, p65, TNF-α, and IL-10. While, in mice receiving the oral administration of terpinen4-ol, the production of TNF-α, IL-10, TLR4, and p65 was suppressed on day 1, 7, and 14 of heat stress. In addition Claudin-2, Occludin mRNA levels were upregulated in mice receiving terpinen4-ol on day 1, 7, and 14 of heat stress. Furthermore, the IL-6, IL-10, TNF-α serum levels were also upregulated in mice under heat stress, but in mice receiving the oral administration of terpinen4-ol, the IL-6, IL-10, TNF-α level was down-regulated on day 1, 7, and 14 of heat stress. Histomorphological examination found that as compared to the control group, the muscle layer thickness and villi height of mice in the heat stress group were significantly reduced, while the changes of the above indicators in the terpinene4-ol groups were improved than those in the heat stress group. In conclusion, the terpinen4-ol has a protective effect on colonic tissue damage induced by heat stress.

Responses of beef calves to long-term heat stress exposure by evaluating growth performance, physiological, blood and behavioral parameters

The objective of this study was to explore the responses of beef calves to long-term heat stress (HS) exposure at various levels in comparison with the animals under thermoneutral conditions by evaluating growth performance, physiological, blood, and behavioural parameters. Data were collected from sixteen beef calves (BW: 136.9 ± 6.23 kg; age: 169.6 ± 4.60 d) kept at four stress levels of designated temperature humidity index (THI): threshold (22-24 °C, 60%; THI = 70 to 73), mild (26-28 °C, 60%; THI = 74 to 76), moderate (29-31 °C, 80%; THI = 81 to 83), and severe (32-34 °C, 80%; THI = 89 to 91) stress levels in climatic controlled chambers. Feed and water intake were recorded daily, and body weight was measured once a week. Blood was sampled every three days to analyse metabolite parameters. Dry matter intake (DMI) (p = 0.069, tendency) and blood glucose levels (p = 0.028) were decreased after sudden exposure to HS conditions (severe THI levels). Also, blood cortisol (p = 0.002), glutamic-oxaloacetic transaminase (GOT) (p = 0.009), blood urea nitrogen (BUN) (p = 0.004) and standing time (p = 0.009) were increased in moderate and severe THI levels compared with threshold after exposure to HS conditions. However, in the severe THI group, blood cortisol (p < 0.05), glucose (p < 0.05), GOT (p < 0.05) and BUN (p < 0.05) levels were returned to normal range after 6-13 days of continuous HS exposure. In conclusion, DMI, blood cortisol, GOT, glucose, BUN, and standing time were closely associated with long-term HS condition in beef calves. In addition, calves exposed to HS modulated their physiological responses that resulted in the regulation of the pertinent blood metabolites in the blood to maintain homeostasis during the long-term HS.

Effect of heat stress on growth and production performance of livestock and poultry: Mechanism to prevention

Heat stress is a widespread phenomenon in domestic animal feeding in tropical and sub-tropical areas that are subjected to a growing negative effect in livestock and poultry due to global warming. It leads to reduced food intake, retarded growth, intestinal disequilibrium, lower reproductive performance, immunity and endocrine disorders in livestock and poultry. Many studies show that the pathogenesis of heat stress is mainly related to oxidative stress, hormone secretion disorder, cytokine imbalance, cell apoptosis, cell autophagy, and abnormal cell function. Its mechanism refers to activation of mitogen-activated protein kinase (MAPK) signaling pathway and nuclear factor kappa B (NF-κB) signaling pathway, the fluctuation of tight junction protein and heat shock protein expression, and protein epigenetic modification. This manuscript reviews the mechanism of heat stress through an insight into the digestive, reproductive, immune, and endocrine system. Lastly, the progress in prevention and control techniques of heat stress has been summarized.

Altered relationship between gluconeogenesis and immunity in broilers exposed to heat stress for different durations

This study determined the relationship between inflammation and gluconeogenesis level in broilers in different durations of heat stress. A total of 240 Ross 308 broilers were offered control and heat stress temperature from 21 to 35 d post-hatch, each experimental group had 8 replications, and each replication obtained 15 broilers. The temperature in the control (Ctrl) group and heat stress group were maintained at 24 ± 1°C and 34 ± 1°C, respectively throughout the experimental period. Based on the duration of heat stress, the heat stress group was divided into 2 subgroups, like, 7-d heat stress (28-day-old broiler) designated ST group and 14-d heat stress (35-day-old broiler) designated the LT group. The ad libitum commercial feed and fresh water were provided to all experimental broilers during the experiment. The growth performance of experimental broilers was calculated at 35 d. However, the liver and blood samples were collected from the Ctrl group in 21 d, as well as these samples were collected from the heat stress ST and LT groups in 28-d and 35-d, respectively. Obvious gene expression of immunity, gluconeogenesis, glycogenolysis, and glycogenesis, as well as glucose-6-phosphate dehydrogenase and adenosine triphosphate was determined in the liver sample. The blood glucose concentration and histopathology of the liver was also examined in the different grouped broilers. Body weight, weight gain, and feed intake significantly decreased in the 35-d heat stress group than the Ctrl group. However, the feed conversion ratio increased at the 35-d heat stress group than the Ctrl group. The amount of glucose-6-phosphate dehydrogenase was significantly higher in ST and LT groups than Ctrl, whereas the blood glucose level was downregulated in the LT group. The amount of adenosine triphosphate was significantly decreased in the LT group than the Ctrl and ST groups. Heat stress acts as an impediment to the general relation between gluconeogenesis and immunity, as well as changes cellular structure. This experiment contributed to the establishment of a relationship between gluconeogenesis and immunity, which affects the growth performance of broilers during heat stress.

Possible Effects of Climate Change on Ixodid Ticks and the Pathogens They Transmit: Predictions and Observations

The global climate has been changing over the last century due to greenhouse gas emissions and will continue to change over this century, accelerating without effective global efforts to reduce emissions. Ticks and tick-borne diseases (TTBDs) are inherently climate-sensitive due to the sensitivity of tick lifecycles to climate. Key direct climate and weather sensitivities include survival of individual ticks, and the duration of development and host-seeking activity of ticks. These sensitivities mean that in some regions a warming climate may increase tick survival, shorten life-cycles and lengthen the duration of tick activity seasons. Indirect effects of climate change on host communities may, with changes in tick abundance, facilitate enhanced transmission of tick-borne pathogens. High temperatures, and extreme weather events (heat, cold, and flooding) are anticipated with climate change, and these may reduce tick survival and pathogen transmission in some locations. Studies of the possible effects of climate change on TTBDs to date generally project poleward range expansion of geographical ranges (with possible contraction of ranges away from the increasingly hot tropics), upslope elevational range spread in mountainous regions, and increased abundance of ticks in many current endemic regions. However, relatively few studies, using long-term (multi-decade) observations, provide evidence of recent range changes of tick populations that could be attributed to recent climate change. Further integrated 'One Health' observational and modeling studies are needed to detect changes in TTBD occurrence, attribute them to climate change, and to develop predictive models of public- and animal-health needs to plan for TTBD emergence.

Impacts of heat stress on immune responses and oxidative stress in farm animals and nutritional strategies for amelioration

Heat stress is one of the greatest challenges for the global livestock industries as increased environmental temperature and humidity compromises animal production during summer leading to devastating economic consequences. Over the last 30 years, significant developments have been achieved in cooling and provision of shade and shelter to mitigate heat stress reducing some of the losses associated with heat stress in farm animals. However, the recent increase in the incidence of heat waves which are also becoming more severe and lasting longer, due to climate change, further accentuates the problem of heat stress. Economic losses associated with heat stress are both direct due to loss in production and animal life, and indirect due to poorer quality products as a result of poor animal health and welfare. Animal health is affected due to impaired immune responses and increased reactive oxygen species production and/or deficiency of antioxidants during heat stress leading to an imbalance between oxidant and antioxidants and resultant oxidative stress. Research over the last 20 years has achieved partial success in understanding the intricacies of heat stress impacts on oxidative stress and immune responses and developing interventions to ameliorate impacts of heat stress, improving immune responses and farm animal health. This paper reviews the body of knowledge on heat stress impacts on immune response in farm animals. The impacts of heat stress on both cell-mediated and humoral immune responses have been discussed identifying the shift in immune response from cell-mediated towards humoral response, thereby weakening the immune status of the animal. Both species and breed differences have been identified as influencing how heat stress impacts the immune status of farm animals. In addition, crosstalk signaling between the immune system and oxidative stress has been considered and the role of antioxidants as potential nutritional strategies to mitigate heat stress has been discussed.

Effect of in-vitro heat stress challenge on the function of blood mononuclear cells from dairy cattle ranked as high, average and low immune responders

Background

The warming climate is causing livestock to experience heat stress at an increasing frequency. Holstein cows are particularly susceptible to heat stress because of their high metabolic rate. Heat stress negatively affects immune function, particularly with respect to the cell-mediated immune response, which leads to increased susceptibility to disease. Cattle identified as having enhanced immune response have lower incidence of disease. Therefore, the objective of this study was to evaluate the impact of in vitro heat challenge on blood mononuclear cells from dairy cattle, that had previously been ranked for immune response, in terms of heat shock protein 70 concentration, nitric oxide production, and cell proliferation.

Results

Blood mononuclear cells from dairy cattle classified as high immune responders, based on their estimated breeding values for antibody and cell-mediated responses, produced a significantly greater concentration of heat shock protein 70 under most heat stress treatments compared to average and low responders, and greater cell-proliferation across all treatments. Similarly, a trend was observed where high responders displayed greater nitric oxide production compared to average and low responders across heat treatments.

Conclusion

Overall, these results suggest that blood mononuclear cells from high immune responder dairy cows are more thermotolerant compared to average and low immune responders.

Dynamic changes in blood immune cell composition and function in Holstein and Jersey steers in response to heat stress

Heat stress has detrimental effects on livestock via diverse immune and physiological changes; heat-stressed animals are rendered susceptible to diverse diseases. However, there is relatively little information available regarding the altered immune responses of domestic animals in heat stress environments, particularly in cattle steers. This study aimed to determine the changes in the immune responses of Holstein and Jersey steers under heat stress. We assessed blood immune cells and their functions in the steers of two breeds under normal and heat stress conditions and found that immune cell proportions and functions were altered in response to different environmental conditions. Heat stress notably reduced the proportions of CD21+MHCII+ B cell populations in both breeds. We also observed breed-specific differences. Under heat stress, in Holstein steers, the expression of myeloperoxidase was reduced in the polymorphonuclear cells, whereas heat stress reduced the WC1+ γδ T cell populations in Jersey steers. Breed-specific changes were also detected based on gene expression. In response to heat stress, the expression of IL-10 and IL-17A increased in Holstein steers alone, whereas that of IL-6 increased in Jersey steers. Moreover, the mRNA expression pattern of heat shock protein genes such as Hsp70 and Hsp90 was significantly increased in only Holstein steers. Collectively, these results indicate that altered blood immunological profiles may provide a potential explanation for the enhanced susceptibility of heat-stressed steers to disease. The findings of this study provide important information that will contribute to developing new strategies to alleviate the detrimental effects of heat stress on steers.

Heat stress and immune response phenotype affect DNA methylation in blood mononuclear cells from Holstein dairy cows

Heat stress negatively affects health and production in cows. Examining the cellular response to heat stress could reveal underlying protective molecular mechanisms associated with superior resilience and ultimately enable selection for more resilient cattle. This type of investigation is increasingly important as future predictions for the patterns of heat waves point to increases in frequency, severity, and duration. Cows identified as high immune responders based on High Immune Response technology (HIR) have lower disease occurrence compared to their average and low immune responder herd-mates. In this study, our goal was to identify epigenetic differences between high and low immune responder cows in response to heat stress. We examined genome-wide DNA methylation of blood mononuclear cells (BMCs) isolated from high and low cows, before and after in vitro heat stress. We identified differential methylation of promoter regions associated with a variety of biological processes including immune function, stress response, apoptosis, and cell signalling. The specific differentially methylated promoter regions differed between samples from high and low cows, and results revealed pathways associated with cellular protection during heat stress.

Methylome Patterns of Cattle Adaptation to Heat Stress

Heat stress has a detrimental impact on cattle health, welfare and productivity by affecting gene expression, metabolism and immune response, but little is known on the epigenetic mechanisms mediating the effect of temperature at the cellular and organism level. In this study, we investigated genome-wide DNA methylation in blood samples collected from 5 bulls of the heat stress resilient Nellore breed and 5 bulls of the Angus that are more heat stress susceptible, exposed to the sun and high temperature-high humidity during the summer season of the Brazilian South-East region. The methylomes were analyzed during and after the exposure by Reduced Representation Bisulfite Sequencing, which provided genome-wide single-base resolution methylation profiles. Significant methylation changes between stressful and recovery periods were observed in 819 genes. Among these, 351 were only seen in Angus, 366 were specific to Nellore, and 102 showed significant changes in methylation patterns in both breeds. KEGG and Gene Ontology (GO) enrichment analyses showed that responses were breed-specific. Interestingly, in Nellore significant genes and pathways were mainly involved in stress responses and cellular defense and were under methylated during heat stress, whereas in Angus the response was less focused. These preliminary results suggest that heat challenge induces changes in methylation patterns in specific loci, which should be further scrutinized to assess their role in heat tolerance.

Chronic temperature stress inhibits reproduction and disrupts endocytosis via chaperone titration in Caenorhabditis elegans

Background

Temperature influences biology at all levels, from altering rates of biochemical reactions to determining sustainability of entire ecosystems. Although extended exposure to elevated temperatures influences organismal phenotypes important for human health, agriculture, and ecology, the molecular mechanisms that drive these responses remain largely unexplored. Prolonged, mild temperature stress (48 h at 28 °C) has been shown to inhibit reproduction in Caenorhabditis elegans without significantly impacting motility or viability.

Results

Analysis of molecular responses to chronic stress using RNA-seq uncovers dramatic effects on the transcriptome that are fundamentally distinct from the well-characterized, acute heat shock response (HSR). While a large portion of the genome is differentially expressed ≥ 4-fold after 48 h at 28 °C, the only major class of oogenesis-associated genes affected is the vitellogenin gene family that encodes for yolk proteins (YPs). Whereas YP mRNAs decrease, the proteins accumulate and mislocalize in the pseudocoelomic space as early as 6 h, well before reproduction declines. A trafficking defect in a second, unrelated fluorescent reporter and a decrease in pre-synaptic neuronal signaling indicate that the YP mislocalization is caused by a generalized defect in endocytosis. Molecular chaperones are involved in both endocytosis and refolding damaged proteins. Decreasing levels of the major HSP70 chaperone, HSP-1, causes similar YP trafficking defects in the absence of stress. Conversely, increasing chaperone levels through overexpression of the transcription factor HSF-1 rescues YP trafficking and restores neuronal signaling.

Conclusions

These data implicate chaperone titration during chronic stress as a molecular mechanism contributing to endocytic defects that influence multiple aspects of organismal physiology. Notably, HSF-1 overexpression improves recovery of viable offspring after exposure to stress. These findings provide important molecular insights into understanding organismal responses to temperature stress as well as phenotypes associated with chronic protein misfolding.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-021-01008-1.

Comprehensive RNA-Seq Profiling Reveals Temporal and Tissue-Specific Changes in Gene Expression in Sprague-Dawley Rats as Response to Heat Stress Challenges

Understanding heat stress physiology and identifying reliable biomarkers are paramount for developing effective management and mitigation strategies. However, little is known about the molecular mechanisms underlying thermal tolerance in animals. In an experimental model of Sprague–Dawley rats subjected to temperatures of 22 ± 1°C (control group; CT) and 42°C for 30 min (H30), 60 min (H60), and 120 min (H120), RNA-sequencing (RNA-Seq) assays were performed for blood (CT and H120), liver (CT, H30, H60, and H120), and adrenal glands (CT, H30, H60, and H120). A total of 53, 1,310, and 1,501 differentially expressed genes (DEGs) were significantly identified in the blood (P < 0.05 and |fold change (FC)| >2), liver (P < 0.01, false discovery rate (FDR)–adjusted P = 0.05 and |FC| >2) and adrenal glands (P < 0.01, FDR-adjusted P = 0.05 and |FC| >2), respectively. Of these, four DEGs, namely Junb, P4ha1, Chordc1, and RT1-Bb, were shared among the three tissues in CT vs. H120 comparison. Functional enrichment analyses of the DEGs identified in the blood (CT vs. H120) revealed 12 biological processes (BPs) and 25 metabolic pathways significantly enriched (FDR = 0.05). In the liver, 133 BPs and three metabolic pathways were significantly detected by comparing CT vs. H30, H60, and H120. Furthermore, 237 BPs were significantly (FDR = 0.05) enriched in the adrenal glands, and no shared metabolic pathways were detected among the different heat-stressed groups of rats. Five and four expression patterns (P < 0.05) were uncovered by 73 and 91 shared DEGs in the liver and adrenal glands, respectively, over the different comparisons. Among these, 69 and 73 genes, respectively, were proposed as candidates for regulating heat stress response in rats. Finally, together with genome-wide association study (GWAS) results in cattle and phenome-wide association studies (PheWAS) analysis in humans, five genes (Slco1b2, Clu, Arntl, Fads1, and Npas2) were considered as being associated with heat stress response across mammal species. The datasets and findings of this study will contribute to a better understanding of heat stress response in mammals and to the development of effective approaches to mitigate heat stress response in livestock through breeding.

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.

Changes in Blood Metabolites and Immune Cells in Holstein and Jersey Dairy Cows by Heat Stress

Simple Summary

As global temperatures rise, thermal stress can be a major problem affecting cows. If they are subjected to heat stress, they are likely to exhibit abnormal metabolic reactions and affect their immune system. However, the relationship between metabolism and immunity during thermal stress and these crosstalk mechanisms remain unclear. Therefore, the aim of this study was to understand the changes in blood immune cell response with the physiological metabolism changes of Holstein and Jersey cows through the biochemistry and flow cytometry branches under thermal stress conditions. We found that various blood metabolites were reduced in both Holsteins and Jerseys by heat stress conditions. There were breed-specific variations in the immune cell population in Holstein and Jersey cows under different environmental conditions. The main findings of this study provide information on the metabolism and immunity changes of two types of cow under heat stress, broadening the potential relationship of these changes.

Abstract

Owing to increasing global temperatures, heat stress is a major problem affecting dairy cows, and abnormal metabolic responses during heat stress likely influence dairy cow immunity. However, the mechanism of this crosstalk between metabolism and immunity during heat stress remains unclear. We used two representative dairy cow breeds, Holstein and Jersey, with distinct heat-resistance characteristics. To understand metabolic and immune responses to seasonal changes, normal environmental and high-heat environmental conditions, we assessed blood metabolites and immune cell populations. In biochemistry analysis from sera, we found that variety blood metabolites were decreased in both Holstein and Jersey cows by heat stress. We assessed changes in immune cell populations in peripheral blood mononuclear cells (PBMCs) using flow cytometry. There were breed-specific differences in immune-cell population changes. Heat stress only increased the proportion of B cells (CD4–CD21+) and heat stress tended to decrease the proportion of monocytes (CD11b+CD172a+) in Holstein cows. Our findings expand the understanding of the common and specific changes in metabolism and immune response of two dairy cow breeds under heat stress conditions.

Alterations in TNF-α and its receptors expression in cows undergoing heat stress

Heat stress is one of the environmental factors that most severely affects milk industry, as it has impact on production, immune responses and reproductive performance. The present study was conducted with high-performance Holando-Argentino cows. Our objective was to study TNF-α and its receptors pattern expression in cows from a region characterized by extreme climatic seasonality. Animals were evaluated in three periods: spring (n = 15), summer (n = 14) and autumn (n = 11). Meteorological records from a local station were used to estimate the temperature and humidity index (THI) by means of an equation previously defined. A THI higher than 68 is indicative of stressing conditions. During the summer period, the animals were exposed to 8.5 ± 1.09 h of heat stress, or THI > 68. In spring, stress hours were reduced to 1.4 ± 0.5 every day, while during the autumn, there were no recorded heat stress events. Expression of TNF-α, and its receptors was determined by qPCR. During the summer, TNF-α and its receptors expression diminished drastically compared to the rest of the year, when stressful conditions were infrequent. We conclude that animals that are not physiologically prepared to resist high temperatures might have a less efficient immune response, reinforcing the need to develop new strategies to improve animal welfare.

Characterization of Short-Term Heat Stress in Holstein Dairy Cows Using Altered Indicators of Metabolomics, Blood Parameters, Milk MicroRNA-216 and Characteristics

Simple Summary

In this study, we characterize the influence of short-term (4 days) heat stress on Holstein cows during early lactation. The use of indicators, such as production performance, physiological variables, blood parameters, micro-RNA expression, and metabolomes, in heat-stressed cows during early lactation—which is a high-stress phase—may provide insights into how to deal with the level of damage to dairy cows, through appropriate nutritional and management strategies. We identify that short-term heat stress has a negative effect, to some extent, on feed and water intake, rectal temperature, heart rate, blood hematology and metabolites, milk characteristics, miRNA expression in milk, and metabolomics in blood.

Abstract

This study aims to characterize the influence of short-term heat stress (HS; 4 day) in early lactating Holstein dairy cows, in terms of triggering blood metabolomics and parameters, milk yield and composition, and milk microRNA expression. Eight cows (milk yield = 30 ± 1.5 kg/day, parity = 1.09 ± 0.05) were homogeneously housed in environmentally controlled chambers, assigned into two groups with respect to the temperature humidity index (THI) at two distinct levels: approximately ~71 (low-temperature, low-humidity; LTLH) and ~86 (high-temperature, high-humidity; HTHH). Average feed intake (FI) dropped about 10 kg in the HTHH group, compared with the LTLH group (p = 0.001), whereas water intake was only numerically higher (p = 0.183) in the HTHH group than in the LTLH group. Physiological parameters, including rectal temperature (p = 0.001) and heart rate (p = 0.038), were significantly higher in the HTHH group than in the LTLH group. Plasma cortisol and haptoglobin were higher (p < 0.05) in the HTHH group, compared to the LTLH group. Milk yield, milk fat yield, 3.5% fat-corrected milk (FCM), and energy-corrected milk (ECM) were lower (p < 0.05) in the HTHH group than in the LTLH group. Higher relative expression of milk miRNA-216 was observed in the HTHH group (p < 0.05). Valine, isoleucine, methionine, phenylalanine, tyrosine, tryptophan, lactic acid, 3-phenylpropionic acid, 1,5-anhydro-D-sorbitol, myo-inositol, and urea were decreased (p < 0.05). These results suggest that early lactating cows are more vulnerable to short-term (4 day) high THI levels—that is, HTHH conditions—compared with LTLH, considering the enormous negative effects observed in measured blood metabolomics and parameters, milk yield and compositions, and milk miRNA-216 expression.

Effect of seasonal thermal stress on oxidative status, immune response and stress hormones of lactating dairy cows

This study aimed to assess the impact of seasonal thermal stress on oxidative stress, immune response, and stress hormones of lactating dairy cows in subtropical regions with different levels of temperature-humidity index (THI). A total of 32 healthy lactating Holstein dairy cows experienced 4 seasons (8 cows/season). The physiological parameters were categorized into low THI (LTHI, THI = 42.97 ± 0.95) in winter, moderate THI (MTHI, THI = 61.84 ± 0.42) in spring and autumn, and high THI period (HTHI, THI = 86.09 ± 0.23) in summer. The blood samples were collected twice in each season to measure oxidative stress, inflammatory and hormonal parameters. Our results showed THI had a positive correlation with the rectal temperature (R 2 = 0.821, P < 0.001) and respiratory rate (R 2 = 0.816, P < 0.001). Dry matter intake, milk yield and fat percentage also significantly differed among groups (P < 0.05). Compared with the MTHI group, the LTHI group exhibited a significant increase in malondialdehyde (MDA) level (P < 0.001), and the HTHI group displayed a significant increase in levels of cortisol, interleukin (IL)-10, IL-1β and tumor necrosis factor-α (P < 0.001). Opposite changes in serum endotoxin and immunoglobulin G levels were observed with the increasing THI (P < 0.001). LTHI notably increased the triiodothyronine level, although the thyroxine level was reduced by LTHI and HTHI compared with the MTHI group. In conclusion, LTHI and HTHI conditions may induce different degrees of oxidative stress, inflammation response, and stress hormone imbalances on lactating dairy cows, therefore environmental management is necessary for the health of dairy cows in extreme weather conditions.

Impacts of climate change on the livestock food supply chain; a review of the evidence

The potential impacts of climate change on current livestock systems worldwide are a major concern, and yet the topic is covered to a limited extent in global reports such as the ones produced by the Intergovernmental Panel on Climate Change. In this article, we review the risk of climate-related impacts along the land-based livestock food supply chain. Although a quantification of the net impacts of climate change on the livestock sector is beyond the reach of our current understanding, there is strong evidence that there will be impacts throughout the supply chain, from farm production to processing operations, storage, transport, retailing and human consumption. The risks of climate-related impacts are highly context-specific but expected to be higher in environments that are already hot and have limited socio-economic and institutional resources for adaptation. Large uncertainties remain as to climate futures and the exposure and responses of the interlinked human and natural systems to climatic changes over time. Consequently, adaptation choices will need to account for a wide range of possible futures, including those with low probability but large consequences.

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Risk results from the interaction of climate-related hazards with the exposure and vulnerability of human and natural systems.

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Climate change will impact the livestock sector throughout the food supply chain⁠—from farm production to human consumption.

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Key hazards relate to climate change trends but also, and importantly, to climate variability and climate extremes.

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Large uncertainties remain as to climate futures and the exposure and responses of the interlinked human and natural systems.

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Adaptation choices will need to account for a wide range of possible futures.

Genomic analyses and biological validation of candidate genes for rectal temperature as an indicator of heat stress in Holstein cattle

Heat stress is a major cause of welfare issues and economic losses to the worldwide dairy cattle industry. Genetic selection for heat tolerance has a great potential to positively affect the dairy industry, as the gains are permanent and cumulative over generations. Rectal temperature (RT) is hypothesized to be a good indicator trait of heat tolerance. Therefore, this study investigated the genetic architecture of RT by estimating genetic parameters, performing genome-wide association studies, and biologically validating potential candidate genes identified to be related to RT in Holstein cattle. A total of 33,013 RT records from 7,598 cows were used in this study. In addition, 1,114 cows were genotyped using the Illumina 150K Bovine BeadChip (Illumina, San Diego, CA). Rectal temperature measurements taken in the morning (AMRT) and in the afternoon (PMRT) are moderately heritable traits, with estimates of 0.09 ± 0.02 and 0.04 ± 0.01, respectively. These 2 traits are also highly genetically correlated (r = 0.90 ± 0.08). A total of 10 SNPs (located on BTA3, BTA4, BTA8, BTA13, BTA14, and BTA29) were found to be significantly associated with AMRT and PMRT. Subsequently, gene expression analyses were performed to validate the key functional genes identified (SPAG17, FAM107B, TSNARE1, RALYL, and PHRF1). This was done through in vitro exposure of peripheral blood mononuclear cells (PBMC) to different temperatures (37°C, 39°C, and 42°C). The relative mRNA expression of 2 genes, FAM107B and PHRF1, significantly changed between the control and heat stressed PBMC. In summary, RT is heritable, and enough genetic variability exists to enable genetic improvement of heat tolerance in Holstein cattle. Important genomic regions were identified and biologically validated; FAM107B and PHRF1 are the main candidate genes identified to influence heat stress response in dairy cattle.

Potential role of specific microRNAs in the regulation of thermal stress response in livestock

Thermal stress is known to have harmful effects on livestock productivity and can cause livestock enterprises considerable financial loss. These effects may be aggravated by climate change. Stress responses to nonspecific systemic actions lead to perturbation of molecular pathways in the organism. The molecular response is regulated in a dynamic and synchronized manner that assurances robustness and flexibility for the restoration of functional and structural homeostasis in stressed cells and tissues. MicroRNAs (miRNAs) are micro molecules of small non-coding RNA that control gene expression at the post-transcriptional level. Recently, various studies have discovered precise types of miRNA that regulate cellular machinery and homeostasis under various types of stress, suggesting a significant role of miRNA in thermal stress responses in animals. The miRNAs revealed in this paper could serve as promising candidates and biomarkers for heat stress and could be used as potential pharmacological targets for mitigating the consequences of thermal stress. Stress miRNA pathways may be associated with thermal stress, which offers some potential approaches to combat the negative impacts of thermal stress in livestock. The review provides new data that can assist the elucidation of the miRNA mechanisms that mediate animals' responses to thermal stress.

Common and Differential Dynamics of the Function of Peripheral Blood Mononuclear Cells between Holstein and Jersey Cows in Heat-Stress Environment

Simple Summary

Seasonal change, particularly changing to hot and humid season, has a negative effect on dairy cows in various ways, including productivity, reproduction, metabolism, and immunity. In high-temperature and humid weather, dairy cows are vulnerable to diseases by weakened immune system. However, the cause of this has not been fully described. Therefore, this study aims to understand changes of specific gene expression and immune pathways based on transcriptome analysis from peripheral blood mononuclear cells of Holstein and Jersey dairy cows between normal and heat-stress environmental conditions. We observed that the two breeds of dairy cow have common and different immune shifts according to the changes of temperature and humidity condition. Overall, the findings of this study improve the understanding of the underlying mechanisms by which seasonal changes affect dairy cow immunity.

Abstract

Heat stress has been reported to affect the immunity of dairy cows. However, the mechanisms through which this occurs are not fully understood. Two breeds of dairy cow, Holstein and Jersey, have distinct characteristics, including productivity, heat resistance, and disease in high-temperature environments. The objective of this study is to understand the dynamics of the immune response of two breeds of dairy cow to environmental change. Ribonucleic acid sequencing (RNA-seq) results were analyzed to characterize the gene expression change of peripheral blood mononuclear cells (PBMCs) in Holstein and Jersey cows between moderate temperature-humidity index (THI) and high THI environmental conditions. Many of the differentially expressed genes (DEGs) identified are associated with critical immunological functions, particularly phagocytosis, chemokines, and cytokine response. Among the DEGs, CXCL3 and IL1A were the top down-regulated genes in both breeds of dairy cow, and many DEGs were related to antimicrobial immunity. Functional analysis revealed that cytokine and chemokine response-associated pathways in both Holstein and Jersey PBMCs were the most important pathways affected by the THI environmental condition. However, there were also breed-specific genes and pathways that altered according to THI environmental condition. Collectively, there were both common and breed-specific altered genes and pathways in Holstein and Jersey cows. The findings of this study expand our understanding of the dynamics of immunity in different breeds of dairy cow between moderate THI and high THI environmental conditions.

Proteome analysis of rainbow trout (Oncorhynchus mykiss) liver responses to chronic heat stress using DIA/SWATH

Aquaculture of rainbow trout (Oncorhynchus mykiss) is severely hampered by high temperatures in summer, and understanding the regulatory mechanisms controlling responses to chronic heat stress may assist the development of measures to relieve heat stress. In the present study, biochemical parameters revealed a strong stress response in rainbow trout at 24 °C, including activation of stress defence and immune systems. Liver proteome analysis under heat stress (24 °C) and control (18 °C) conditions using DIA/SWATH identified precursors (90,827), peptides (67,028), proteins (6770) and protein groups (5124), among which 460 differentially abundant proteins (DAPs; q-value < 0.05, fold change >1.5), 201 and 259 were up- and down-regulated, respectively. Many were related to heat shock proteins (HSPs), metabolism and immunity. Gene Ontology (GO) analysis showed that some DAPs induced at high temperature were involved in regulating cell homeostasis, metabolism, adaptive stress and stimulation. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis identified metabolic pathways, protein processing in endoplasmic reticulum, PPAR signalling, and complement and coagulation cascades. Protein-protein interaction (PPI) network analysis indicated that HSP90b1 and C3 may cooperative to affect cell membrane integrity under heat stress. Our findings assist the development of strategies to relieve heat stress in rainbow trout.

The Effect of Stress on Reproduction and Reproductive Technologies in Beef Cattle-A Review

Researchers have contributed by increasing our understanding of the factors affecting reproduction in beef, mainly physical health and nutrition aspects, which have been main concerns during decades. Animal welfare is of outmost relevance in all animal production systems and it is strongly associated to stress. Stress responses involve endocrine, paracrine and neural systems and the consequences of this stress on the reproductive efficiency of specifically, beef cattle and bulls, need to be highlighted. We, therefore, describe the fundamentals of stress and its quantification, focusing in beef herds, reviewing the highly valuable pieces of research, already implemented in this field. We examine major factors (stressors) contributing to stress in beef cattle and their effects on the animals, their reproductive performance and the success of reproductive biotechnologies. We include terms such as acclimatization, acclimation or temperament, very relevant in beef systems. We examine specifically the management stress due to handling, social environment and hierarchy or weaning effects; nutritional stress; and thermal stress (not only heat stress) and also review the influence of these stressors on reproductive performance and effectiveness of reproductive biotechnologies in beef herds. A final message on the attention that should be devoted to these factors is highlighted.

Lipopolysaccharide triggers different transcriptional signatures in taurine and indicine cattle macrophages: Reactive oxygen species and potential outcomes to the development of immune response to infections

Macrophages are classified upon activation as classical activated M1 and M2 anti-inflammatory regulatory populations. This macrophage polarization is well characterized in humans and mice, but M1/M2 profile in cattle has been far less explored. Bos primigenius taurus (taurine) and Bos primigenius indicus (indicine) cattle display contrasting levels of resistance to infection and parasitic diseases such as C57BL/6J and Balb/c murine experimental models of parasite infection outcomes based on genetic background. Thus, we investigated the differential gene expression profile of unstimulated and LPS stimulated monocyte-derived macrophages (MDMs) from Holstein (taurine) and Gir (indicine) breeds using RNA sequencing methodology. For unstimulated MDMs, the contrast between Holstein and Gir breeds identified 163 Differentially Expressed Genes (DEGs) highlighting the higher expression of C-C chemokine receptor type five (CCR5) and BOLA-DQ genes in Gir animals. LPS-stimulated MDMs from Gir and Holstein animals displayed 1,257 DEGs enriched for cell adhesion and inflammatory responses. Gir MDMs cells displayed a higher expression of M1 related genes like Nitric Oxide Synthase 2 (NOS2), Toll like receptor 4 (TLR4), Nuclear factor NF-kappa-B 2 (NFKB2) in addition to higher levels of transcripts for proinflammatory cytokines, chemokines, complement factors and the acute phase protein Serum Amyloid A (SAA). We also showed that gene expression of inflammatory M1 population markers, complement and SAA genes was higher in Gir in buffy coat peripheral cells in addition to nitric oxide concentration in MDMs supernatant and animal serum. Co-expression analyses revealed that Holstein and Gir animals showed different transcriptional signatures in the MDMs response to LPS that impact on cell cycle regulation, leukocyte migration and extracellular matrix organization biological processes. Overall, the results suggest that Gir animals show a natural propensity to generate a more pronounced M1 inflammatory response than Holstein, which might account for a faster immune response favouring resistance to many infection diseases.

Alteration of chemokine production in bovine endometrial epithelial and stromal cells under heat stress conditions

After parturition, cows frequently develop uterine bacterial infections, resulting in the onset of endometritis. To eliminate the bacteria, bovine endometrial cells secrete chemokines, such as IL-6 and MCP1, which attract macrophages (MΦs) to the subepithelial stroma. These attracted MΦs are not only involved in bacterial elimination but also the orchestration of inflammation and tissue repair. These immune responses aid in the recovery from endometritis; however, the recovery from endometritis takes longer in summer than in any other season. Based on these findings, we hypothesized that heat stress (HS) affects the chemokine production in endometrial cells. To confirm this hypothesis, we compared IL-6 and MCP1 production induced by lipopolysaccharide (LPS) in bovine endometrial epithelial and stromal cells under normal (38.5°C) and HS conditions (40.5°C). In the endometrial epithelial cells, IL-6 production stimulated by LPS was significantly (p < .05) suppressed under HS conditions. MCP1 production in endometrial epithelial cells was not detected under both the control and HS conditions regardless of the presence of LPS. Moreover, LPS significantly (p < .05) stimulated IL-6 and MCP1 production in endometrial stromal cells. Moreover, HS significantly (p < .05) enhanced their production compared to that under the control conditions. In addition, HS did not affect the migration ability of MΦs; however, the supernatant of the endometrial stromal cells cultured under the HS condition significantly (p < .05) attracted the MΦs when compared to the control condition. These results suggest that HS disrupts chemokine production in two types of endometrial cells and alters the distribution of MΦs in the endometrium during the summer.

Effect of Lonicera japonica extract on lactation performance, antioxidant status, and endocrine and immune function in heat-stressed mid-lactation dairy cows

Here, we examined the effects of Lonicera japonica extract (LJE) on lactation performance, antioxidant status, and endocrine and immune function in heat-stressed mid-lactation dairy cows. Twenty-four healthy Chinese Holstein mid-lactation dairy cows, all with similar milk yield (30.0 ± 1.0 kg/d), parity (2.5 ± 0.3), and days in milk (105 ± 5 d) were allocated to 4 groups using a randomized complete block design: a negative control group (without LJE supplementation; CON) and groups that received LJE at 14, 28, and 56 g/d. The experiment lasted 10 wk over a hot summer, with a pre-feeding period of 2 wk. Cows were exposed to heat stress, as the average temperature-humidity index was greater than 72. The results showed that LJE had no effect on respiration rate; however, it reduced the rectal temperature of dairy cows experiencing heat stress in both a linear and quadratic manner; the lowest (39.03°C) was recorded for the LJE-28 group, lower than the CON group. Supplementation with LJE did not affect dry matter intake, milk yield, or milk composition. The majority of biochemical parameters in serum were unaffected by supplementation with different amounts of LJE; the exception was creatinine, which was reduced quadratically. Compared with the CON group, serum triiodothyronine concentrations increased significantly in the LJE-28 group. Addition of LJE to the diet increased thyroxine concentrations quadratically; values peaked at 18.62 ng/mL in the LJE-28 group. Furthermore, supplementation with increasing amounts of LJE quadratically increased the activity of glutathione peroxidase and total antioxidant capacity in serum but decreased concentration of malondialdehyde. Although we detected no differences in the concentrations of IgA, IgM, or cytokines, dairy cows in the LJE-28 group had higher IgG and IL-4 concentrations than did cows in the CON group. Supplementation with LJE increased concentrations of IgG and IL-4 in the serum quadratically but decreased that of IL-2. Finally, heat shock protein 72 concentrations in the serum tended to fall quadratically as the amount of LJE increased. In summary, LJE had no negative effects on lactation performance but helped to alleviate heat stress by improving antioxidant status and promoting endocrine and immune functions. Supplementation with LJE at 28 g/d is recommended for lactating dairy cows experiencing heat stress during hot summers.