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.

Global dynamics of highly pathogenic avian influenza outbreaks in poultry between 2005 and 2016-Focus on distance and rate of spread

Highly pathogenic avian influenza (HPAI) is of major importance for human and animal health because of high morbidity and mortality in poultry and the potential for transmission of this zoonotic pathogen to humans. Knowledge of HPAI epidemiology in avian populations and practical information on the temporal and spatial spread of the disease after introduction into a country is important in order to enhance the capacity of predicting and managing epidemics to minimize the negative impacts on human and animal health. Using data reported to the World Organisation for Animal Health between 2005 and 2017 by 199 countries for 14,129 outbreaks in poultry, we used a spatial and time-series analysis to determine that: (a) During the last 12 years, there were two major global peaks in the number of countries affected by HPAI with 23% and 26% of countries affected in 2006 and 2016. (b) Based on the seasonality analysis, spread is the lowest in September, begins to rise in October, and peaks in February. (c) The median distance HPAI outbreaks spread from the index outbreak was 111 km, while the median apparent rate of spread of outbreaks was 1.9 km/day. (d) In 39% of HPAI events, the disease did not spread beyond the index outbreak and the median maximum spread from the index outbreak per event was 45 km. (e) The distance HPAI outbreaks spread from the index outbreak was significantly negatively correlated with the number of outbreaks during the same time period, indicating that the spread of HPAI was lower during global panzootics than during periods of low transmission. These findings are of major importance for veterinary services to design and implement surveillance measures for improving preparedness to minimize the impacts of this disease.

Reproductiveaxis gene regulation during photostimulation and photorefractoriness in Yangzhou goose ganders

Background

The Yangzhou goose is a long-day breeding bird that has been increasingly produced in China. Artificial lighting programs are used for controlling its reproductive activities. This study investigated the regulations of photostimulation and photorefractoriness that govern the onset and cessation of the breeding period.

Results

Increasing the daily photoperiod from 8 to 12 h rapidly stimulated testis development and increased plasma testosterone concentrations, with peak levels being reached 2 months after the photoperiod increase. Subsequently, testicular activities, testicular weight, spermatogenesis, and plasma testosterone concentrations declined steadily and reached to the nadir at 5 months after the 12-hour photoperiod. Throughout the experiment, plasma concentrations of triiodothyronine and thyroxine changed in reciprocal fashions to that of testosterone. The stimulation of reproductive activities caused by the increasing photoperiod was associated with increases in gonadotropin-releasing hormone (GnRH), but decreases in gonadotropin-inhibitory hormone (GnIH) and vasoactive intestinal peptide (VIP) gene messenger RNA (mRNA) levels in the hypothalamus. In the pituitary gland, the levels of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) mRNA abruptly increased during the longer 12-hour photoperiod. The occurrence of photorefractoriness was associated with increased GnIH gene transcription by over 250-fold, together with increased VIP mRNA levels in the hypothalamus, and then prolactin and thyroid-stimulating hormone in the pituitary gland. FSH receptor, LH receptor, and StAR mRNA levels in the testis changed in ways paralleling those of testicular weight and testosterone concentrations.

Conclusions

The seasonal reproductive activities in Yangzhou geese were directly stimulated by a long photoperiod via upregulation of GnRH gene transcription, downregulation of GnIH, VIP gene transcription, and stimulation of gonadotrophin. Development of photorefractoriness was characterized by hyper-regulation of GnIH gene transcription in the hypothalamus, in addition of upregulation of VIP and TRH gene transcription, and that of their receptors, in the pituitary gland.

Differential responses of the somatotropic and thyroid axes to environmental temperature changes in the green iguana

Growth hormone (GH), together with thyroid hormones (TH), regulates growth and development, and has critical effects on vertebrate metabolism. In ectotherms, these physiological processes are strongly influenced by environmental temperature. In reptiles, however, little is known about the direct influences of this factor on the somatotropic and thyroid axes. Therefore, the aim of this study was to describe the effects of both acute (48h) and chronic (2weeks) exposure to sub-optimal temperatures (25 and 18°C) upon somatotropic and thyroid axis function of the green iguana, in comparison to the control temperature (30-35°C). We found a significant increase in GH release (2.0-fold at 25°C and 1.9-fold at 18°C) and GH mRNA expression (up to 3.7-fold), mainly under chronic exposure conditions. The serum concentration of insulin-like growth factor-I (IGF-I) was significantly greater after chronic exposure (18.5±2.3 at 25°C; 15.92±3.4 at 18°C; vs. 9.3±1.21ng/ml at 35°C), while hepatic IGF-I mRNA expression increased up to 6.8-fold. Somatotropic axis may be regulated, under acute conditions, by thyrotropin-releasing hormone (TRH) that significantly increased its hypothalamic concentration (1.45 times) and mRNA expression (0.9-fold above control), respectively; and somatostatin (mRNA expression increased 1.0-1.2 times above control); and under chronic treatment, by pituitary adenylate cyclase-activating peptide (PACAP mRNA expression was increased from 0.4 to 0.6 times). Also, it was shown that, under control conditions, injection of TRH stimulated a significant increase in circulating GH. On the other hand, while there was a significant rise in the hypothalamic content of TRH and its mRNA expression, this hormone did not appear to influence the thyroid axis activity, which showed a severe diminution in all conditions of cold exposure, as indicated by the decreases in thyrotropin (TSH) mRNA expression (up to one-eight of the control), serum T4 (from 11.6±1.09 to 5.3±0.58ng/ml, after 2weeks at 18°C) and T3 (from 0.87±0.09 to 0.05±0.01ng/ml, under chronic conditions at 25°C), and Type-2 deiodinase (D2) activity (from 992.5±224 to 213.6±26.4fmolI(125)T4/mgh). The reduction in thyroid activity correlates with the down-regulation of metabolism as suggested by the decrease in the serum glucose and free fatty acid levels. These changes apparently were independent of a possible stress response, at least under acute exposure to both temperatures and in chronic treatment to 25°C, since serum corticosterone had no significant changes in these conditions, while at chronic 18°C exposure, a slight increase (0.38 times above control) was found. Thus, these data suggest that the reptilian somatotropic and thyroid axes have differential responses to cold exposure, and that GH and TRH may play important roles associated to adaptation mechanisms that support temperature acclimation in the green iguana.

Oxidant and enzymatic antioxidant status (gene expression and activity) in the brain of chickens with cold-induced pulmonary hypertension

To evaluate oxidant and antioxidant status of the brain (hindbrain, midbrain, and forebrain) in chickens with cold-induced pulmonary hypertension, the measurements of lipid peroxidation, protein oxidation, antioxidant capacity, enzymatic activity, and gene expression (for catalase, glutathione peroxidase, and superoxide dismutases) were done. There were high lipid peroxidation/protein oxidation and low antioxidant capacity in the hindbrain of cold-induced pulmonary hypertensive chickens compared to control (P < 0.05). In the hypertensive chickens, superoxide dismutase activity was decreased (forebrain, midbrain, and hindbrain), while catalase activity was increased (forebrain and midbrain) (P < 0.05). Glutathione peroxidase activity did not change. Relative gene expression of catalase and superoxide dismutases (1 and 2) was downregulated, while glutathione peroxidase was upregulated in the brain of the cold-induced pulmonary hypertensive chickens. Probably, these situations in the oxidant and antioxidant status of the brain especially hindbrain may change its function at cardiovascular center and sympathetic nervous system to exacerbate pulmonary hypertension.

Timing of influenza A(H5N1) in poultry and humans and seasonal influenza activity worldwide, 2004-2013

Co-circulation of H5N1 in poultry and humans during seasonal influenza epidemic periods signals the need for enhanced surveillance and biosafety measures.

Co-circulation of influenza A(H5N1) and seasonal influenza viruses among humans and animals could lead to co-infections, reassortment, and emergence of novel viruses with pandemic potential. We assessed the timing of subtype H5N1 outbreaks among poultry, human H5N1 cases, and human seasonal influenza in 8 countries that reported 97% of all human H5N1 cases and 90% of all poultry H5N1 outbreaks. In these countries, most outbreaks among poultry (7,001/11,331, 62%) and half of human cases (313/625, 50%) occurred during January–March. Human H5N1 cases occurred in 167 (45%) of 372 months during which outbreaks among poultry occurred, compared with 59 (10%) of 574 months that had no outbreaks among poultry. Human H5N1 cases also occurred in 59 (22%) of 267 months during seasonal influenza periods. To reduce risk for co-infection, surveillance and control of H5N1 should be enhanced during January–March, when H5N1 outbreaks typically occur and overlap with seasonal influenza virus circulation.

Cold stress induces antioxidants and Hsps in chicken immune organs

The aim of this study was to investigate the effects of cold stress on oxidative indexes, immune function, and the expression levels of heat shock protein (Hsp90, Hsp70, Hsp60, Hsp40, and Hsp27) in immune organs of chickens. Two hundred forty 15-day-old male chickens were randomly divided into 12 groups and kept under the temperature of (12 ± 1) °C for acute and chronic cold stress. There were one control group and five treatment groups for acute cold stress and three control groups and three treatment groups for chronic cold stress. The results showed that cold stress influence the activities of antioxidant enzymes in the immune organs. The activities of SOD and GSH-Px were first increased then decreased, and activity of total antioxidation capacity (T-AOC) was significantly decreased (P < 0.05) at the acute cold stress in chicks; however, T-AOC activities were significantly increased (P < 0.05) at the chronic cold stress in these tissues. Cold stress induced higher level of malondialdehyde (MDA) in chicken immune organs. In addition, the cytokine contents were increased in cold stress groups. As one protective factor, the expression levels of Hsps were increased significantly (P < 0.05) in both cold stress groups. These results suggested that cold stress induced the oxidative stress in the three tissues and influenced immune function of chicks. Higher expression of Hsps (Hsp90, Hsp70, Hsp60, Hsp40, and Hsp27) may play a role in protecting immune organs against cold stress.

Stress- and diet-induced fat gain is controlled by NPY in catecholaminergic neurons

Neuropeptide Y (NPY) and noradrenaline are commonly co-expressed in sympathetic neurons. Both are key regulators of energy homeostasis and critical for stress-coping. However, little is known about the specific function of NPY in the catecholaminergic system in these regulations. Here we show that mice with NPY expression only in the noradrenergic and adrenergic cells of the catecholaminergic system (catNPY) exhibited exacerbated diet-induced obesity, lower body and brown adipose tissue temperatures compared to WT and NPY^−/− mice under a HFD. Furthermore, chronic stress increased adiposity and serum corticosterone level in WT but not NPY^−/− mice. Re-introducing NPY specifically to the catecholaminergic system in catNPY mice restored stress responsiveness associated with increased respiratory exchange ratio and decreased liver pACC to tACC ratio. These results demonstrate catecholaminergic NPY signalling is critical in mediating diet- and chronic stress-induced fat gain via effects on diet-induced thermogenesis and stress-induced increases in corticosterone levels and lipogenic capacity.

The role of heat shock proteins in inflammatory injury induced by cold stress in chicken hearts

The aim of this study was to investigate the effects of cold stress on the expression levels of heat shock proteins (Hsps90, 70, 60, 40, and 27) and inflammatory factors (iNOS, COX-2, NF-κB, TNF-α, and PTGEs) and oxidative indexes in hearts of chickens. Two hundred forty 15-day-old male chickens were randomly divided into 12 groups and kept at the temperature of 12 ± 1 °C for acute and chronic cold stress. There were one control group and five treatment groups for acute cold stress, three control groups, and three treatment groups for chronic cold stress. After cold stress, malondialdehyde level increased in chicken heart; the activity of superoxide dismutase and glutathione peroxidase in the heart first increased and then decreased. The inflammatory factors mRNA levels were increased in cold stress groups relative to control groups. The histopathological analysis showed that heart tissues were seriously injured in the cold stress group. Additionally, the mRNA levels of Hsps (70, 60, 40, and 27) increased significantly (P < 0.05) in the cold stress groups relative to the corresponding control group. Meanwhile, the mRNA level and protein expression of Hsp90 decreased significantly (P < 0.05) in the stress group, and showed a gradually decreasing tendency. These results suggested that the levels of inflammatory factors and Hsps expression levels in heart tissues can be influenced by cold stress. Hsps commonly played an important role in the protection of the heart after cold stress.

Influence of inflammatory pathway markers on oxidative stress induced by cold stress in intestine of quails

The cold temperature reduces the immunity and re-production activities of the poultry. This study aimed to investigate the effects of acute and chronic cold exposure on the regulation of nuclear factor-kappa B (NF-κB) and tumor necrosis factor-α (TNF-α) expression in the duodenum, jejunum, and ileum of quails. In this study, 96 15-d-old male quails were randomly allocated into 12 groups (eight each group) for exposure to acute (up to 12h) and chronic (up to 20 days) cold stress (12 ± 1°C). Antioxidative function was examined by superoxide dismutase (SOD) and oxidative damage was examined by malondialdehyde (MDA) detection. qRT-PCR was performed to analyze expression of NF-κB and TNF-α, and DNA sequencing was performed to analyze PCR products. The data showed that under cold stress, the SOD level decreased, and the MDA level had the tendency to increase in duodenum, jejunum and ileum of quails, while the mRNA expression of NF-κB increased and TNF-α decreased in duodenum, jejunum and ileum of quails. The data from the current study indicated that both acute and chronic cold stresses were able to induce inflammatory responses in the duodenum, jejunum and ileum, which might be due to the cold-damaged intestinal oxidative stress.

Oxidative macromolecular alterations in the rat central nervous system in response to experimentally co-induced chlorpyrifos and cold stress: a comparative assessment in aging rats

Reactive oxygen species are generated as a result of a number of physiological and pathological processes which can promote multiple forms of oxidative damage including protein oxidation, and thereby influence the function of a diverse array of cellular processes. In our previous study we have reported that co-exposure to chlorpyrifos and cold stress in aging rats markedly influence the toxic outcome as a result of oxidative stress. In the present study, key neurochemical/enzymes were measured in order to evaluate the macromolecular alterations in response to experimentally co-induced chlorpyrifos and cold stress (15 and 20°C) either concurrently or individually in vivo for 48 h in discrete regions of brain and spinal cord of different age group rats. CPF and cold stress exposure either individually or in combination substantially increased the activity/levels of protein carbonyls, AST, ALT and decreased protein thiols, DNA, RNA and total proteins in discrete regions of CNS. Overall, the effects of co-exposure were appreciably different from either of the exposures. However, synergistic-action of CPF and cold stress at 15°C showed higher dyshomeostasis in comparison with CPF and cold stress alone and together at 20°C indicating the extent of oxidative macromolecular damage in discrete regions of brain and spinal cord. Furthermore, the present study demonstrates that macromolecular oxidative damage is highly pronounced in neonates and juveniles than the young adults.