"Unveiling the impacts of climatic cold events on the cardiovascular health in animal models"

Climate change is increasingly driving extreme weather events, leading to drastic temperature fluctuations worldwide. While overall temperatures rise, many regions are simultaneously experiencing severe cold spells that threaten the health of human populations, especially to vulnerable populations including the elderly and those with pre-existing conditions. Exposure to cold stress triggers significant physiological and biochemical disruptions. As cardiovascular diseases (CVDs) rank among the leading causes of global morbidity and mortality, the exacerbation of these conditions by cold exposure underscores critical public health challenges. The complex pathophysiological processes in cold-induced CVDs require careful analysis at an organ-system level, making animal models an ideal tool for replicating human physiological and molecular responses in a controlled environment. However, a detailed mechanism linking cold exposure and cardiovascular dysfunction remains incompletely understood, particularly in the context of animal models. Therefore, this comprehensive review aims to address and analyze from traditional rodent models to less conventional ruminants, broilers, canines, and primate animal models to understand cold stress-induced CVDs, with an extensive account of the potential molecular mechanisms and pathways such as oxidative stress, inflammation, vasomotor dysfunction, and apoptosis, along with emerging roles of cold shock proteins (CSPs), etc. We also delve into various potential therapeutic approaches and preventive measures in cold stress conditions. In conclusion, this review is the first to comprehensively address the underexplored cardiovascular complications arising from cold stress and their underlying mechanisms, particularly using animal models. Furthermore, it provides a foundation for advancing the development of more effective and targeted therapies through translational research.

Intermittent and mild cold stimulation enhances immune function of broilers via co-regulation of CIRP and TRPM8 on NF-κB and MAPK signaling pathways

Improving immune function is an important indicator for establishing cold adaptation in broilers. In the study, to explore the effects and molecular mechanisms of intermittent and mild cold stimulation (IMCS) on the immune function of broilers, CIRP and TRPM8, induced by cold stimulation, as well as the NF-κB and MAPK pathways which play an important role in immune response, were selected to investigate. A total of 192 one-day-old broilers (Ross 308) were selected and randomly divided into the control group (CC) and the cold stimulation group (CS). The broilers in CC were raised at normal feeding temperature from d 1 to 43, while the broilers in CS were subjected to cold stimulation from day 15 to 35, with a temperature 3 °C below that of the CC group for 5 h, at 1 d intervals. The results showed that IMCS had little effect on the broiler hearts, and the myocardial structure was not damaged. On d 22, IMCS significantly increased the mRNA levels of CIRP, TRPM8, P65, P38, COX-2, TNF-α, IFN- γ, IL-6, IL-10, and the protein levels of CIRP, P65, P38, IL-1β and iNOS in the hearts, and the levels of CIRP and all cytokines in the serum (P ≤ 0.05). The mRNA and protein levels of IκB-α were significantly reduced (P ≤ 0.05). On d 36, the mRNA levels of TRPM8, P65, ERK, and IL-10 in the hearts and the content of COX-2 in the serum in CS were increased significantly (P ≤ 0.05), while the mRNA levels of IκB-α, P38, and IL-1β were decreased significantly (P ≤ 0.05). On d 43, IMCS significantly upregulated the mRNA levels of TRPM8, IFN- γ, IL-4, IL-6, IL-10, and the protein levels of IκB-α, P38, and the levels of iNOS, TNF-α, IL6 and IL10 in the serum (P ≤ 0.05); whereas it significantly downregulated CIRP, JNK, P38, iNOS, TNF-α mRNA levels, and CIRP, P65, ERK, JNK, IL1β and iNOS protein levels (P ≤ 0.05). Therefore, IMCS can enhance broiler immune function through co-regulation of CIRP and TRPM8 on the NF-κB and MAPK pathways, which facilitate the cold adaptation in broilers.

Intermittent mild cold acclimation ameliorates intestinal inflammation and immune dysfunction in acute cold-stressed broilers by regulating the TLR4/MyD88/NF-κB pathway

To investigate the potential protective effect of prior cold stimulation on broiler intestine induced by acute cold stress (ACS). A total of 384 one-day-old broilers were divided into control (CON), ACS, cold stimulation Ⅰ (CS3+ACS), and cold stimulation Ⅱ (CS9+ACS) groups. Broilers in CON and ACS groups were reared normally, and birds in CS3+ACS and CS9+ACS groups were reared at 3℃ and 9℃ below CON group for 5 h, respectively, on alternate days from d 15 to 35. Broilers in ACS, CS3+ACS, and CS9+ACS groups were subjected to 10℃ for 24 h on d 43. Eventually, small intestine tissues were collected for histopathological observation and indexes detection. The results showed that intestinal tissues in all ACS-broilers exhibited inflammatory cell infiltrates, microvilli disruption, reduced villus length in jejunum and increased crypt depth in jejunum and ileum. Whereas these phenomena were relatively light in CS3+ACS group. Compared to CON group, mRNA expression of the TLR4/MyD88/NF-κB pathway-related genes (TLR4, MyD88, NF-κBp65, COX-2, iNOS, PTGEs, TNF-α), Th1/Th17-derived cytokines (IL-1β, IL-2, IL-8, IL-12, IFN-γ, IL-17), and HSPs (HSP40, HSP60, HSP70, HSP90) was upregulated (P < 0.05), and that of Th2-deviated cytokines (IL-4, IL-6, IL-10, IL-13) and IκBα was downregulated (P < 0.05) in small intestine in almost all ACS-broilers. Compared to ACS group, mRNA expression of most of the TLR4/MyD88/NF-κB pathway-related genes, Th1/Th17-derived cytokines, and HSPs was downregulated and that of Th2-derived cytokines was upregulated in CS3+ACS group (P < 0.05). Protein expression levels of TLR4, MyD88, p-p65/p65, p-IκBα/IκBα, IKK, TNF-α, IL-1β, IL-10, and HSPs were similar to their mRNA expression. The concentration of sIgA and activities of CAT, SOD, and GSH-px were decreased and MDA and H2O2 were increased in ACS and CS9+ACS groups compared to CON group (P < 0.05). Therefore, cold stress caused oxidative stress and inflammation, leading to gut immune dysfunction; while mild cold stimulation at 3℃ below normal rearing temperature alleviated cold stress-induced intestinal injure and dysfunction by modulating the TLR4/MyD88/NF-κB pathway in broilers.

Omics analysis of the effect of cold normal saline stress through gastric gavage on LPS induced mice

Cold stress is a significant environmental stimulus that negatively affects the health, production, and welfare of animals and birds. However, the specific effects of cold stimulation combined with lipopolysaccharide (LPS) on the mouse intestine remain poorly understood. Therefore, we designed this research to explore the effect of cold stimulation + LPS on mice intestine via microbiome and microbiota sequencing. Forty-eight mice were randomly divided into four experimental groups (n = 12): Control (CC), LPS-induced (CL), cold normal saline-induced (MC) and LPS + cold normal saline-induced (ML). Our results showed body weight was similar among different groups of mice. However, the body weight of mice in groups CC and CL were slightly higher compared to those in groups MC and ML. The results of gene expressions reflected that CL and ML exposure caused gut injury and barrier dysfunction, as evident by decreased ZO-1, OCCLUDIN (P < 0.01), and CASPASE-1 (P < 0.01) expression in the intestine of mice. Moreover, we found that cold stress induced oxidative stress in LPS-challenged mice by increasing malondialdehyde (MDA) accumulation and decreasing the antioxidant capacity [glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), total and antioxidant capacity (T-AOC)]. The cold stress promoted inflammatory response by increased IL-1β in mice treated with cold normal saline + LPS. Whereas, microbiome sequencing revealed differential abundance in four phyla and 24 genera among the mouse groups. Metabolism analysis demonstrated the presence of 4,320 metabolites in mice, with 43 up-regulated and 19 down-regulated in CC vs. MC animals, as well as 1,046 up-regulated and 428 down-regulated in ML vs. CL animals. It is Concluded that cold stress enhances intestinal damage by disrupting the balance of gut microbiota and metabolites, while our findings contribute in improving management practices of livestock in during cold seasons.

Effects of Glycine Supplementation in Drinking Water on the Growth Performance, Intestinal Development, and Genes Expression in the Jejunum of Chicks

Glycine, the most basic amino acid found in nature, is considered an essential amino acid for chicks. However, the precise understanding of high concentrations of glycine's significance in promoting the growth performance of chicks, as well as its impact on intestinal development, re-mains limited. Consequently, the objective of this study was to investigate the effects of glycine supplementation in drinking water on growth performance, intestine morphology, and development in newly hatched chicks. In this study, 200 newly born chicks were selected and pro-vided with a supplementation of 0.5%, 1%, and 2% glycine in their drinking water during their first week of life. The results revealed that glycine supplementation in drinking water could significantly increase the average daily gain of chicks from days 7 to 14. Furthermore, a significant difference was observed between the group supplemented with 1% glycine and the control group. Concurrently, this glycine supplementation increased the villus height and the ratio of the villus height to crypt depth in jejunum on both day 7 and day 14. Glycine supplementation in drinking water significantly affected the mRNA expression level of the ZO-1, GCLM, and rBAT genes in jejunum, which may have certain effects on the mucosal immune defense, cellular antioxidant stress capacity, and amino acid absorption. Overall, the findings of this study indicate that glycine supplementation in drinking water can enhance the growth performance of chicks and promote their intestine development.

Cold stimulation causes oxidative stress, inflammatory response and apoptosis in broiler heart via regulating Nrf2/HO-1 and NF-κB pathway

To investigate the effect of cold stimulation on heart, 300 1-day-old female broilers were divided into control (CON) and two cold stimulation (CS3 and CS9) groups. Birds in CON group were reared in normal ambient temperature during day 1-43; while birds in CS3 and CS9 groups were reared at 3 °C and 9 °C below CON group for 5 h at 1-day intervals from day 15 to day 35, respectively. Heart tissues were collected at day 22, 29, 36, and 43 to determine the indexes related to oxidative stress, inflammation and apoptosis. The H&E staining displayed that inflammatory cell infiltration and myocardial fiber break were obviously observed in CS9 group, and cardiac pathological score in CS9 group was higher than CON and CS3 groups (P < 0.05) at day 22, 36, and 43. Overall, compared to CON group, the concentrations of MDA and H2O2 were elevated, the activities of SOD, CAT, GPx, and T-AOC were reduced, and mRNA expression of CAT, GPx, SOD, nuclear factor-erythroid 2-related factor 2 (Nrf2), and heme oxygenase-1 (HO-1) was downregulated in CS9 group at each time-point (P < 0.05). Compared to CON group, mRNA expression of NF-κBp65, COX-2, iNOS, PTGEs, TNF-α, and IL-1β, and mRNA and protein expression of Bax, Bak, Cyt-c, caspase-3, and caspase-9 were increased, while Bcl-2 and Bcl-2/Bax ratio were decreased in CS9 group (P < 0.05) at the most detected time-points. There were no significant differences in the levels of indexes associated with oxidative stress, Nrf2/HO-1 antioxidant system, inflammation, and apoptosis between CON and CS3 groups at the most detected time-points (P > 0.05). Therefore, this study suggests that severe cold stimulation at 9 °C below normal rearing temperature induces cardiomyocyte inflammation and apoptosis by regulating Nrf2/HO-1 pathway-related oxidative stress in broilers, and mild cold stimulation of CS3 group can improve the adaptability of hearts to cold environment.

Intermittent and Mild Cold Stimulation Maintains Immune Function Stability through Increasing the Levels of Intestinal Barrier Genes of Broilers

In order to improve the adaptability of broilers to low-temperature environments and their ability to resist acute cold stress (ACS), 240 one-day-old broilers were selected and randomly divided into three groups. The control treatment (CC) group was raised at the conventional feeding temperature from 1-43 days (d), the cold stimulation treatment (CS) group was kept at 3 °C below the temperature of CC at 1 d intervals for 3 and 6 h from 15 to 35 d, namely, CS3 and CS6, respectively. Then, all broilers were kept at 20 °C from 36 to 43 d. ACS was then carried out at 44 d, and the ambient temperature was dropped to 10 °C for 6 h. The study investigated the production performance, as well as levels of intestinal barrier genes (including Claudin-1, E-cadherin, Occludin, ZO-1, ZO-2 and Mucin2), secretory IgA in duodenum and jejunum, and immunoglobulins (IgA and IgG) in serum. The results showed that IMCS could increase the daily weight gain and decrease the feed conversion ratio. During IMCS, the expression levels of intestinal barrier genes were up-regulated and the content of secretory IgA was increased. When IMCS ceased for one week, the level of immunoglobulins in serum stabilized, and the expression levels of Occludin, ZO-2 and Mucin2 still maintained high levels. After ACS, broilers that received IMCS training maintained high levels of intestinal barrier genes and secretory IgA.

Acute cold stress induces intestinal injury via CIRP-TLR4-IRE1 signaling pathway in pre-starter broilers

BACKGROUND

Cold stress is a common environmental stress in broiler chicks. Cold-inducible RNA-binding protein (CIRP) is a conserved cold shock protein that can regulate inflammatory response through Toll-like receptor 4 (TLR4). The mechanism that how CIRP involves in the regulation of cold stress in broilers remains unclear.

METHODS AND RESULTS

In this study, 360 7-day-old healthy male SZ901 chicks were selected and randomly allocated to four groups, and then subjected to acute cold exposure at the ambient temperature of 12 ± 1 °C for 0 h, 4 h, 8 h, and 12 h, respectively. After cold exposure, abdominall skin temperature, gene expression of CIRP-TLR4-IRE1 signaling pathway in ileum mucosa, and small intestinal structure were measured. The results showed that cold exposure decreased abdominall skin temperature, upregulated the gene expression of endoplasmic reticulum stress (ERS) markers IRE1, inflammatory factors IL-1β, IL-6, IL-10, TNF-α, and tight junction proteins ZO-1 and Occludin in ileum of chicks compared with the control group with no (0 h) cold exposure. Compared with the control group, a long time cold exposure upregulated the gene expression of CIRP, TLR4, GRP78, NF-κB in ileum mucosa, and decreased the villus height and V/C of small intestine.

CONCLUSIONS

The above results suggest that acute cold stress induces endoplasmic reticulum stress via upregulating the gene expression of CIRP-TLR4-IRE1 signaling pathway, and results in the structural damage of chick intestine.

Effect of intermittent mild cold stimulation on intestinal immune function and the anti-stress ability of broilers

A total of 240 healthy 1-day-old Ross 308 male broilers were randomly divided into 3 groups (CS0 group, CS3 group, and CS6 group), with 5 replicates in each group and 16 broilers in each replicate, in order to evaluate the effects of intermittent mild cold stimulation (IMCS) on the intestinal immune function and anti-cold stress ability of broilers after acute cold stress. The mRNA expression levels of cytokines and Toll-like receptors (TLRs) in the duodenum and jejunum were detected at the end of cold stimulation (36 d), 2 wk after recovery (50 d), and after acute cold stress (Y6). In addition, the mRNA and protein expression levels of heat shock proteins (HSPs) were measured before and after acute cold stress. The experimental data were statistically processed using 1-way ANOVA and Duncan's multiple comparisons. The results showed that the mRNA expression levels of IL2, IL8, IFN γ, TLR7, and TLR21 in the duodenum and IL2 and IFN γ in jejunum were significantly higher in the CS6 group than in the CS0 and CS3 groups at 36 d (P < 0.05). All TLR levels in the jejunum were significantly lower in the CS3 group than in the CS0 and CS6 groups at 36 d (P < 0.05). After 6 h of acute cold stress, in the duodenum, the mRNA expression levels of IL6 and IL8 were significantly decreased in the CS0 and CS6 groups compared to levels at 50 d (P < 0.05), while levels in the CS3 group remained stable (P > 0.05). Compared with 50 d, the expression level of HSP mRNA in the jejunum in the CS3 group was relatively stable compared to that in the CS0 and CS6 groups after acute cold stress (P > 0.05). At the protein level, the HSP60 expression level in the duodenum and HSP40, HSP60, and HSP70 expression levels in the jejunum were significantly higher in the CS3 group than in the CS0 and CS6 groups after acute cold stress (P < 0.05). In conclusion, cold stimulation training at 3℃/3 h lower than the conventional feeding temperature can improve the intestinal immune function and anti-stress ability of broilers.

Glucose supplementation improves intestinal amino acid transport and muscle amino acid pool in pigs during chronic cold exposure

Mammals in northern regions chronically suffer from low temperatures during autumn-winter seasons. The aim of this study was to investigate the response of intestinal amino acid transport and the amino acid pool in muscle to chronic cold exposure via Min pig models (cold adaptation) and Yorkshire pig models (non-cold adaptation). Furthermore, this study explored the beneficial effects of glucose supplementation on small intestinal amino acid transport and amino acid pool in muscle of cold-exposed Yorkshire pigs. Min pigs (Exp. 1) and Yorkshire pigs (Exp. 2) were divided into a control group (17 °C, n = 6) and chronic cold exposure group (7 °C, n = 6), respectively. Twelve Yorkshire pigs (Exp. 3) were divided into a cold control group and cold glucose supplementation group (8 °C). The results showed that chronic cold exposure inhibited peptide transporter protein 1 (PepT1) and excitatory amino acid transporter 3 (EAAT3) expression in ileal mucosa and cationic amino acid transporter-1 (CAT-1) in the jejunal mucosa of Yorkshire pigs (P < 0.05). In contrast, CAT-1, PepT1 and EAAT3 expression was enhanced in the duodenal mucosa of Min pigs (P < 0.05). Branched amino acids (BCAA) in the muscle of Yorkshire pigs were consumed by chronic cold exposure, accompanied by increased muscle RING-finger protein-1 (MuRF1) and muscle atrophy F-box (atrogin-1) expression (P < 0.05). More importantly, reduced concentrations of dystrophin were detected in the muscle of Yorkshire pigs (P < 0.05). However, glycine concentration in the muscle of Min pigs was raised (P < 0.05). In the absence of interaction between chronic cold exposure and glucose supplementation, glucose supplementation improved CAT-1 expression in the jejunal mucosa and PepT1 expression in the ileal mucosa of cold-exposed Yorkshire pigs (P < 0.05). It also improved BCAA and inhibited MuRF1 and atrogin-1 expression in muscle (P < 0.05). Moreover, dystrophin concentration was improved by glucose supplementation (P < 0.05). In summary, chronic cold exposure inhibits amino acid absorption in the small intestine, depletes BCAA and promotes protein degradation in muscle. Glucose supplementation ameliorates the negative effects of chronic cold exposure on amino acid transport and the amino acid pool in muscle.

Effects of Acute Cold Stress after Intermittent Cold Stimulation on Immune-Related Molecules, Intestinal Barrier Genes, and Heat Shock Proteins in Broiler Ileum

Cold stress will have a negative impact on animal welfare and health. In order to explore the effect of intermittent cold stimulation training on the cold resistance of broilers. Immune-related and intestinal barrier genes were detected before and after acute cold stress (ACS), aiming to find an optimal cold stimulation training method. A total of 240 1-day-old Ross broilers (Gallus) were divided into three groups (G1, G2, and G3), each with 5 replicates (16 chickens each replicate). The broilers of G1 were raised at normal temperature, while the broilers of G2 and G3 were treated with cold stimulation at 3 °C lower than the G1 for 3 h and 6 h from 15 to 35 d, respectively, at one-day intervals. At 50 d, the ambient temperature for all groups was reduced to 10 °C for six hours. The results demonstrated that before ACS, IL6, IL17, TLR21, and HSP40 mRNA levels in G3 were apparently down-regulated (p < 0.05), while IL8 and Claudin-1 mRNA levels were significantly up-regulated compared with G1 (p < 0.05). After ACS, IL2, IL6, and IL8 expression levels in G3 were lower than those in G2 (p < 0.05). Compared to G2, Claudin-1, HSP90 mRNA levels, HSP40, and HSP70 protein levels were increased in G3 (p < 0.05). The mRNA levels of TLR5, Mucin2, and Claudin-1 in G2 and IL6, IL8, and TLR4 in G3 were down-regulated after ACS, while IL2, IL6, and IL17 mRNA levels in G2 and HSP40 protein levels in G3 were up-regulated after ACS (p < 0.05). Comprehensive investigation shows that cold stimulation at 3 °C lower than the normal feeding temperature for six hours at one day intervals can enhanced immune function and maintain the stability of intestinal barrier function to lessen the adverse effects on ACS in broilers.

Effect of mild intermittent cold stimulation on thymus immune function in broilers

This study aims to assess the effect of intermittent and mild cold stimulation (IMCS) on thymus function and the ability of 1-day-old male Ross 308 broilers to withstand cold. Four hundred broilers were reared under normal and mild cold temperatures at 3°C below the normal feeding temperature and were subjected to acute cold stress (ACS) at 10°C on d 50 at 7 am for 6 h, 12 h, and 24 h. We determined the expression levels of toll-like receptors (TLRs), cytokines and avian β-defencins (AvBDs), encoding genes in thymus of broilers at 22, 36, 43, and 50 d of age, and the serum ACTH and cortisol (CORT) levels at 50 d of age. At D22 and D36, the mRNA expression levels of TLRs and AvBDs genes in CS groups were generally significantly decreased (P < 0.05). The lowest expression levels were found in birds submitted to intermittent and mild cold stimulation training for 5 h (CS5 group) on d 22 and 36 of development (P < 0.05). At D43 and D49 after IMCS, mRNA expression levels of most TLRs and AvBDs were significantly lower than those in CC group (P < 0.05), and that mRNA expression levels of all TLRs and most AvBDs in CS5 group had the same change trend with age as those in CC group (P > 0.05). At D22 and D36, mRNA expression levels of different cytokines in each CS groups were different (P < 0.05). mRNA expression levels of IL-2, IL-4, IL-6, IL-8, IL-17, and IFN-α all reached the highest values in the CS5 group at D36 (P < 0.05). The levels of ACTH and CORT in all IMCS-treated birds changed in varying degrees after ACS, but there was no significant change in CS5 group (P > 0.05). Collectively, different cold stimulation schemes could modulate thymus immune function of broilers by maintaining homeostasis and enhancing cold resistance. In particular, the optimal cold adaptation scheme was at 3°C below the conventional feeding temperature for 5 h.

Rubber (Hevea brasiliensis) seed oil supplementation attenuates immunological stress and inflammatory response in lipopolysaccharide-challenged laying hens

This study was conducted to investigate the effect of PUFA-enriched rubber (Hevea brasiliensis) seed oil (RSO) supplementation in diets on the productive performance, plasma biochemical parameters, immune response, and inflammation in lipopolysaccharide (LPS)-challenged laying hens. Two hundred and forty 25-wk-old Lohmann Brown laying hens were randomly divided into 5 treatments, each including 4 replicates with 12 birds per replicate. The control group and LPS-challenged group were fed a corn-soybean-basal diet; 3 RSO-supplemented groups were fed experimental diets containing 1, 2, and 4% RSO for a feeding period of 4 wk. On the 15, 18, 21, 24, and 27 d of the RSO supplementation period of 4 wk, hens were injected intraperitoneally with LPS at 1 mg/kg body weight (challenge group and RSO-supplemented groups) or with the same amount of saline (control group). The results showed that the addition of RSO promoted laying performance by increasing egg production, total egg weight, daily egg mass, and feed intake in comparison to the LPS-challenged laying hens (P < 0.05). In addition, compared with laying hens stimulated with LPS, the analysis of blood cell and plasma parameters revealed that hens in RSO-supplemented groups had significantly lower levels (P < 0.05) of white blood cells (WBC), lymphocytes (LYM), aspartate aminotransferase (AST) activity, immunoglobulin A (IgA), triiodothyronine (T3), interleukin-2 (IL-2), and tumor necrosis factor-α (TNF-α). Further, RSO supplementation significantly reduced the mRNA expression of toll-like receptor 4 (TLR4), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), interleukin-6 (IL-6), and interleukin-1β (IL-1β) of the ileum, spleen, and liver in LPS-challenged laying hens (P < 0.05), suggesting that the anti-inflammatory mechanism of RSO is related to the TLR4/NF-κB signaling pathway. In conclusion, RSO supplementation in diets could improve laying performance, attenuate immunological stress, and inhibit the inflammatory response in LPS-challenged laying hens, especially at the dietary inclusion of 4% RSO. This study will provide an insight into the application of RSO to positively contribute to overall health and welfare in laying hens.

Early social contact alters the community structure and functions of the faecal microbiome in suckling-growing piglets

Social contact during suckling, in an enriched social environment, can reduce the aggressive behaviours of piglets during regrouping at weaning, and improve their production performance and welfare. The aim of this study was to determine the possible impact of suckling social contact on gut microbes. We performed 16S rRNA sequencing to measure the faecal microbial structure and function in piglets experiencing social contact. Eighteen-litter piglets were allocated to two treatments: an early continuous social contact (CSC) group where piglets from adjacent pens shared a mutual pen starting at 14 days postpartum and a control (CON) group where piglets had no contact with individuals from adjacent pens during the suckling period. The piglets were regrouped at 36 days of age. The litter weights at 35 and 63 days of age were measured. Faecal samples were randomly collected at 16, 35, 42, and 63 days of age and faecal DNA was determined. The results showed that the litter weight of piglets in the CSC group was significantly decreased at 63 days compared with the CON group. Continuous social contact also significantly decreased the microbial richness at 16 and 35 days of age (P < 0.05). Firmicutes was the most abundant bacterial phylum in both groups at all detected time-points and the abundance increased with social contact. At the genus level, Lactobacillus was the most abundant bacterium after weaning and the abundance increased in the piglets with social contact. Compared with the faecal microbiota of control piglets, a total of 22 genera at 16 days, 20 genera at 35 days, 12 genera at 42 days, and 27 genera at 63 days in the faeces of CSC piglets were observed to be significantly different in abundance (linear discriminant analysis score > 3, P < 0.05). Furthermore, functional analysis of the microbial composition showed that the changes induced by early CSC mainly altered the relative abundance of metabolic and related pathways. The social contact notably had an effect on the abundance of microbial pathways for amino acid and carbohydrate metabolism. In conclusion, CSC changed the microbial composition in the faeces of piglets, which might have a negative effect on nutrient metabolism for the suckling-growing piglets. Our study provided new insight into the influence of social contact on the suckling-growing piglets.

Environmental Stress in Chickens and the Potential Effectiveness of Dietary Vitamin Supplementation

Environmental stressors can promote the vulnerability of animals to infections; it is therefore, essential to understand how stressors affect the immune system, the adaptive capacity of animals to respond, and effective techniques in managing stress. This review highlights scientific evidence regarding environmental stress challenge models and the potential effectiveness of vitamin supplementation. The major environmental stressors discussed are heat and cold stress, feed restriction, stocking density, and pollutants. Much work has been done to identify the effects of environmental stress in broilers and layers, while few involved other types of poultry. Studies indicated that chickens' performance, health, and welfare are compromised when challenged with environmental stress. These stressors result in physiological alterations, behavioral changes, decreased egg and meat quality, tissue and intestinal damage, and high mortalities. The application of vitamins with other nutritional approaches can help in combating these environmental stressors in chickens. Poultry birds do not synthesize sufficient vitamins during stressful periods. It is therefore suggested that chicken diets are supplemented with vitamins when subjected to environmental stress. Combination of vitamins are considered more efficient than the use of individual vitamins in alleviating environmental stress in chickens.

Intermittent mild cold stimulation improves the immunity and cold resistance of spleens in broilers

In order to investigate the effect of intermittent mild cold stimulation (IMCS) on immune function of spleens and adaptability to cold stress in broilers, 400 healthy 1-day-old Ross-308 chickens were divided into 5 groups: CC (control) reared in normal thermal environment from 1 to 49 d; CS3, CS4, CS5, and CS6 (treatments) raised at 3°C below the temperature of CC for 3, 4, 5, or 6 h at 1-d intervals from 15 to 35 d, respectively. Subsequently, CS3-6 was raised at 20°C from 36 to 49 d. At 50 d, all groups were exposed to acute cold stress (ACS) for 12 h. The spleen immunity index at 22, 29, 36, 43, and 49 d, expression levels of toll-like receptors (TLRs), cytokines and immunoglobulins at 22, 43, and 49 d and heat shock proteins (HSPs) before and after ACS at 50 d were examined. The spleen index of broilers aged 22 to 49 d did not differ between CS and CC (P > 0.05), and the spleen index of CS5 was higher than that of CS3 at 49 d (P < 0.05). The mRNA levels of TLR5, TLR15, TLR21, and IL-2 in CS3, TLR3, TLR4, TLR15, TLR21, IL-2, IL-6, and IFN-ϒ in CS4, TLR1, TLR3, TLR4, TLR21, IL-2, IFN-a, IFN-ϒ, IgA, and IgG in CS6, but all TLRs, immunoglobulins and cytokines except IFN-ϒ in CS5 differential expressed stably compared with CC at 43 and 49 d (P < 0.05). Compared with Pre-ACS, the mRNA levels of HSP60, HSP70, and HSP90 were upregulated in CS after ACS (P < 0.05). Except for HSP90 mRNA and HSP70 protein in CS6, and HSP90 protein in CS3, the levels of HSPs after ACS in all treatment groups were higher than those in CC (P < 0.05), and the highest HSPs levels after ACS were found in CS5. We concluded that IMCS could enhance immunity of spleens and adaptability to ACS in broilers, besides CS5 was the optimal program.

Effect of dietary serine supplementation on performance, egg quality, serum indices, and ileal mucosal immunity in laying hens fed a low crude protein diet

This study was designed to evaluate the effect of dietary Ser on performance, egg quality, serum indices, and ileal mucosal immunity in laying hens fed low crude protein (LCP), essential amino acids (EAA) balanced diets. A total of 480 Hy-Line Brown layers at 24 wk of age were randomly assigned into 5 dietary treatments with 8 replicates of 12 birds each. Treatments included a control diet (16.49% CP), and 4 LCP, EAA balanced diets (14.05% CP) supplemented with 0, 0.114%, 0.306%, 0.498% L-Ser, respectively. Dietary Ser supplementation linearly increased hen-day egg production (HDEP; P < 0.05) and decreased feed-to-egg ratio (P < 0.05) among LCP groups from wk 6 to 10, and the optimal HDEP of layers occurred at Ser level of 0.498%. At the end of wk 10, birds in the control had higher albumen height and thick white proportion than those fed the LCP diet without Ser addition (P < 0.05), and presented a lower yolk color score than all LCP groups (P < 0.05). Among LCP groups, serum total protein and globulin contents were significantly increased by dietary Ser addition at the levels of 0.306% and 0.498% (P < 0.05), and had a linear response to the supplemental Ser levels (P < 0.05). Furthermore, dietary 0.498% Ser supplementation significantly increased serum immunoglobulin G and immunoglobulin M contents (P < 0.05) and up-regulated the expression of mucin 2, secretory immunoglobulin A, and relevant glycosyltransferases of O-glycosylation in ileal mucosa (P < 0.05). The increased expression of proinflammatory cytokines IFN-γ and IL-1β induced by LCP diets (P < 0.05) was reversed following 0.498% Ser addition (P < 0.05). Collectively, dietary CP reduction by 2.44% could maintain the productive performance of layers when it was fortified with certain EAA, though poor albumen quality, and ileal inflammation were occurred. The addition of Ser to LCP diets improved performance probably through enhancing humoral and ileal mucosal immunity and attenuating the ileal inflammation of layers.

Possibilities of Using Phyto-Preparations to Increase the Adaptive Capabilities of the Organism of Test Animals in Swimming

Background: To study the possibilities of using phytopreparations to increase the adaptive capabilities of the animals on which the experiments were conducted in swimming. Methods: 100 mongrel male rats were divided into 5 groups of 20 animals in each one. For 30 days running, the animals were immersed for 10 min in a bath with water at a temperature of +4 °C. In addition to cold exposure, the animals of the first three groups were injected per os with stress protectors 30 min before the immersion in water. The rats of the first group received an inhibitor of the enzyme gamma-butyrobetaine hydroxylase, the second group was given an extract of Eleutherococcus, and the third group took an extract of Ligusticum wallichii. As a placebo, to control the effect of the stress protectors, the rats of the fourth group were injected per os with 0.9% NaCl solution, and the animals in the fifth group were not given any drugs. On days 1, 4 and 30 of the experiment, five randomly selected animals from each group were decapitated, the heart and liver were removed, and the activity of tissue enzymes—superoxide dismutase (SOD), glutathione peroxidase (GPO), alanine aminotransferase (ALT), and aspartate aminotransferase (AST)—was analyzed. Results: The animals in the control group displayed a decrease in the activity of most of the studied enzymes, increasing from the 1st to the 30th day of the experiment. The NaCl solution had practically no effect on the analyzed parameters. Against the use of the enzyme gamma-butyrobetaine hydroxylase inhibitor, the activity of the enzymes did not change as compared with the pre-intervention level. On the first day of ingestion, the effects of the Ligusticum wallichii extract were similar to those of the enzyme gamma-butyrobetaine hydroxylase inhibitor. On the 30th day of ingestion, the effects of the Eleutherococcus extract were practically indistinguishable from those of the enzyme gamma-butyrobetaine hydroxylase inhibitor. Conclusions: The data obtained suggest the presence of cytoprotective effects in the two phytopreparations that are similar to the enzyme gamma-butyrobetaine hydroxylase inhibitor. In this case, the effect of the extract of Ligusticum wallichii is more pronounced under the acute stress conditions, and the extract of Eleutherococcus, under the chronic stress conditions.

Effects of cold stress on growth performance, serum biochemistry, intestinal barrier molecules, and adenosine monophosphate-activated protein kinase in broilers

The homeostasis dysfunctions caused by cold stress remain a threat to intestinal health, particularly for young broiler chickens. We hypothesized that adenosine monophosphate-activated protein kinase (AMPK) was involved in the regulation of cold stress on intestinal health. This study aimed to examine the effect of cold stress for 72 h on growth performance, serum biochemistry, intestinal barrier molecules, and AMPK in broilers. A total of 144 10-day-old male Arbor Acres broilers were subjected to temperature treatments (control 28  ± 1 °C vs cold stress 16 ± 1 °C) for 72 h. Growth performance was monitored, serum was collected for the analysis of physiological parameters, and jejunal mucosa was sampled for the determination of tight junction (TJ) proteins, heat shock proteins, and AMPK signaling molecules. Results showed that 72 h cold treatment reduced average BW gain and increased the feed conversion ratio of the broilers (P < 0.05). Cold stress for 72 h increased blood endotoxin, aspartate aminotransferase, glucose, and low-density lipoprotein cholesterol levels (P < 0.05). Moreover, 72 h cold treatment up-regulated jejunal Occludin, zonula occludin 1, inducible nitric oxide synthase, heat shock factor 1, and AMPKα1 gene expression (P < 0.05) but had no obvious effect on total AMPK protein expression (P > 0.05). In conclusion, cold stress significantly reduced the growth performance of broiler chickens. The intestinal barrier function might be impaired, and enhanced bacterial translocation might occur. The unregulated gene expression of TJ proteins implied the remodeling of intestinal barrier. The change of AMPK suggested the possible relationship between intestinal energy metabolism and barrier function under cold stress.

Effects of Intermittent Mild Cold Stimulation on mRNA Expression of Immunoglobulins, Cytokines, and Toll-Like Receptors in the Small Intestine of Broilers

Simple Summary

Cold stress has been associated with adverse effects on health and welfare of broilers. Whilst several studies have shown that long-term sustained and mild cold stimulation can improve immune function, little is known of the effects of intermittent cold stimulation on immune modulation in broilers. In this study, broilers were submitted to cold stimulation of 3 °C below than the usual rearing temperature during 3 and 6 h every two days during 43 days to explore its effect on the intestinal immunity. The findings confirm that appropriate mild cold stimulation has an overall positive influence on the intestinal immunity of broilers. The mild cold stimulation tested in this study is cost-effective and likely enhances overall health of broilers.

Abstract

Appropriate cold stimulation can improve immune function and stress tolerance in broilers. In order to investigate the effect of intermittent mild cold stimulation on the intestinal immunity of broilers, 240 healthy one-day-old Ross 308 chickens were randomly divided into three groups: the control group (CC) housed in climatic chambers under usual rearing ambient temperature with a gradual 3.5 °C decrease per week; group II (C3) and group III (C6) to which cold stimulation at 3 °C below the temperature used in CC was applied every two days for 3 and 6 h, respectively, from day 15 to 35, and at the same temperature used in CC from day 35 to 43. The mRNA expression levels of immunoglobulins (IgA and IgG), cytokines (IL2, IL6, IL8, IL17, and IFNγ), and Toll-like receptors (TLR2, TLR4, TLR5, TLR7, and TLR21) were investigated in duodenum, jejunum, and ileum tissue samples on days 22, 29, 35, and 43. From day 15 to 35, mRNA expression of IL2 and IFNγ was increased in the intestine of broilers. After one week of cold stimulation on day 43, mRNA levels of immunoglobulins, cytokines, and Toll-like receptors (TLRs) stabilized. Collectively, the findings indicate that cold stimulation at 3 °C below the usual rearing temperature had a positive impact on intestinal immunity of broilers.

Effects of selenide chitosan sulfate on glutathione system in hepatocytes and specific pathogen-free chickens

This study aimed to investigate the effects of selenide chitosan sulfate (Se-CTS-S) on glutathione (GSH) system in hepatocytes and chickens. Chitosan, sodium selenite (Na₂SeO₃), selenide chitosan, chitosan sulfate (CTS-S), and Se-CTS-S were added to the culture medium and the basal diets; glutathione peroxidase (GSH-Px) activity, GSH content, total antioxidant capacity (T-AOC), and mRNA levels of cellular GPx (GPx-1) and phospholipid hydroperoxide GPx (GPx-4) in vivo and in vitro were determined. The results showed that Se-CTS-S increased (P < 0.05) GPx-1 and GPx-4 mRNA levels in hepatocytes and livers, and GSH-Px activity, GSH content, and T-AOC in the medium, hepatocytes, plasma, and livers compared with the control and chitosan treatments. Compared with CTS-S, Se-CTS-S treatments increased (P < 0.05) GPx-1 and GPx-4 mRNA levels in hepatocytes and livers, and GSH-Px activity, GSH content, and T-AOC capacity in the medium, hepatocytes, and livers. Compared with Na₂SeO₃ and CTS-Se, Se-CTS-S increased (P < 0.05) GPx-1 mRNA levels in hepatocytes and livers, GPx-4 mRNA levels in hepatocytes and livers, GSH-Px activity in the medium, hepatocytes, and livers, GSH contents in plasma and livers, and T-AOC in the medium, plasma, and livers. Thus, Se-CTS-S showed better biological activity that mainly benefited from the synergistic effects of Se and sulfate on GSH system.

Selenium deficiency exacerbates LPS-induced necroptosis by regulating miR-16-5p targeting PI3K in chicken tracheal tissue

Multiple tissue necrosis is one of the morphological features of selenium deficiency-mediated injury. MicroRNA (miRNA) participates in the occurrence and development of necroptosis by regulating target genes. Necroptosis is a programmed form of necrosis, and it is closely related to lipopolysaccharide (LPS)-induced injury. Our aim was to investigate whether Se deficiency can promote tracheal injury caused by LPS through miRNA-induced necroptosis. By establishing models of tracheal injury in Se-deficient chickens, we verified the targeting relationship between chicken-derived miR-16-5p and PI3K through bioinformatics, qRT-PCR and WB analyses, and we measured the changes in the expression of genes related to the PI3K/AKT pathway, RIP3/MLKL pathway and MAPK pathway and of heat shock proteins. Under the condition of Se deficiency, the following results were observed: PI3K/AKT expression decreased with the upregulation of miR-16-5p, the expression of necroptosis-related factors (TNF-α, RIP1, FADD, RIP3 and MLKL) increased, and the expression of Caspase 8 significantly decreased (p < 0.05). Light microscopy observations indicated that cell necrosis was the main pathological change due to Se deficiency injury in the tracheal epithelium. The MAPK pathway was activated, and HSP expression was upregulated, indicating that the MAPK pathway and HSPs are both involved in Se deficiency-mediated necroptosis. In addition, Se deficiency promoted the expression of necroptosis-related genes in LPS-treated chickens (p < 0.05), and the pathological changes of cell necrosis were more obvious. In conclusion, we demonstrated that Se deficiency regulates the miR-16-5p-PI3K/AKT pathway and exacerbates LPS-induced necroptosis in chicken tracheal epithelial cells by activating necroptosis-related genes.

Heat shock protein 70 protects the quail cecum against oxidant stress, inflammatory injury, and microbiota imbalance induced by cold stress

The intent of this study was to investigate the effects of cold stress on oxidative indexes, inflammatory factors, and microbiota in the quail cecum. A total of 192 male quails (15-day-old) were randomly divided into 12 groups (16 in each group) and were exposed to acute (up to 12 h) and chronic (up to 20 D) cold stress at 12 ± 1°C. After cold stress treatment, we examined morphological damage, oxidative stress indexes, inflammatory factors, and intestinal microbiota. Results of morphological examination showed that both acute and chronic cold stress can lead to cecal tissue injury. In addition, both acute and chronic cold stress, especially chronic cold stress can influence the activity of oxidative stress mediators. Glutathione (GSH) and glutathione peroxidase (GSH-Px) activities decreased significantly (p < 0.05), while the nitric oxide (NO) content and inducible nitric oxide synthase (iNOS) activity increased significantly (p < 0.05). Moreover, mRNA levels of inflammatory factors cyclooxygenase-2 (COX-2), prostaglandin E synthase (PTGES), and heat shock protein 70 (Hsp70) were higher in both acute and chronic cold stress groups when compared with the control group (p < 0.05). Furthermore, the intestinal microbiota was changed in both the acute and chronic cold stress groups. These results suggested that cold stress caused oxidative stress and inflammatory injury in cecal tissues, influenced cecal microbiota, and increased expression of Hsp70, which may contribute in protecting the cecum against cold stress in quails.

Proper cold stimulation starting at an earlier age can enhance immunity and improve adaptability to cold stress in broilers

The effects of long-term cold stimulation on the immune function of ileum and adaptability to cold stress in broilers were examined. A total of 360 Arbor Acres broilers was divided into 3 groups and four replicates per group. C (control) was reared in normal thermal environment. C-3 and C-12 (treatments) were kept in cold condition of 3 or 12°C lower than the temperature of C from days 8 to 42. At day 42, all the groups were exposed to an acute cold stress challenge, designated as S, S-3, and S-12. The mRNA levels of immune molecules and heat shock proteins as well as oxidative stress-related indicators in ileum tissues, and immunoglobulins contents in serum were examined at 14, 42, and 43 d of age. The C-3 regimen had no adverse effect on production performance, whereas the C-12 regimen reduced the production performance relative to C (P < 0.05). At day 42, C-3 had higher levels of immune indexes (P < 0.05), whereas C-12 had lower levels than C (P < 0.05). No differences in levels of oxidative stress-related indicators were found between C and C-3 at day 42 (P > 0.05). S-3 had higher levels of immune indexes and lower levels of oxidative stress-related indicators (P < 0.05), as compared to S and S-12. The results suggest that 34 d of cold stimulation at 3°C lower than the normal temperature had no adverse impacts on production performance but enhanced the immunity of ileum and adaptability to acute cold challenge in broilers.

Effects of Acute Cold Stress After Long-Term Cold Stimulation on Antioxidant Status, Heat Shock Proteins, Inflammation and Immune Cytokines in Broiler Heart

To investigate the effects of acute cold stress (ACS) on chicken heart after cold stimulation, female broilers were raised in either normal (C) or gradually decreasing temperatures (CS I and CS II) for 34 days followed by a 24 h ACS at 7°C. Cardiac tissues were collected from the pre-ACS and ACS time points to analyze the histopathological changes, antioxidant status and the expression of heat shock proteins, inflammatory factors and immune-related cytokines. The CS II heart tissues showed shrunken cell membranes and nuclei, disordered or ruptured myocardial fibers, higher MDA content and upregulation in HSP27, HSP40, HSP70, NF-κB, COX-2, PTGEs, iNOS, TNF-α and IL-4 mRNAs, and in protein levels of HSP40, NF-κB and iNOS and reduction in CAT, GSH-px and SOD activity, as well as HSP90 and IFN-γ levels compared to the control tissues before ACS. In contrast, the HSPs were significantly increased, and the inflammatory and immune related factors were unaltered prior to the ACS in the CS I compared to the C group. Following ACS, MDA content was significantly increased and antioxidant activity was significantly decreased in the CS I and CS II groups compared to the C group. The levels of HSP27, HSP70, HSP90, inflammatory factors and IL-4 were significantly reduced and that of IFN-γ was significantly increased in CS I broiler hearts; the reverse trends were seen in CS II relative to CS I. Compared to the pre-ACS levels, that of HSP27, HSP40, HSP60, inflammatory factors and IL-4 were increased and IFN-γ was decreased in the C and CS II groups after ACS. Therefore, cold stimulation at drastically lower temperatures induced cardiac damage, which was further aggravated by ACS. In contrast, cold stimulation at only 3°C lower than normal temperature improved the adaptability of the broilers to ACS.