How climatic changes could affect meat quality

Heat Stress Trends in Regions of Intensive Turkey Production in Germany-A Challenge in Times of Climate Change

This study analyzed trends of enthalpy and the temperature-humidity index (THI) over a period of 50 years in outer air, which lead to severe heat stress in turkeys. Weather station data from 15 German districts with high densities of turkey production were used to investigate the heat input into the barns. Therefore, the parameters of enthalpy and THI with specified thresholds were used for heat stress assessment. Trends in extreme weather situations where these thresholds were exceeded were analyzed and tested for significance using the Mann-Kendall test. In all districts, the heat load increased between 1973 and 2022 for both parameters. Statistically significant heat stress trends were found in 9 of the 15 districts for enthalpy and 14 out of 15 districts for THI. Thus, the established THI thresholds seem to be more sensitive for the detection of heat stress than the chosen enthalpy values. As heat stress is an important issue and a rising concern in times of climate change, farmers and constructors of farm animal facilities should take this into account in future sustainable work.

Review: The role of heat shock proteins in chicken: Insights into stress adaptation and health

This review article aimed to provide readers with a comprehensive understanding of the function of heat shock proteins (HSPs) in chicken physiology, stress response, and overall poultry health. With the increasing challenges faced by the livestock industry, particularly the poultry sector, due to climate change-induced high ambient temperatures, heat stress (HS) has become a critical concern. HS disrupts the thermal balance in poultry, leading to detrimental effects on growth, immune function, and overall health. HSPs play a pivotal role in mitigating the impacts of HS in chickens. These molecular chaperones are involved in protein folding, unfolding, and assembly, and they are classified into several families based on their size, including small molecule HSPs, HSP40, HSP60, HSP70, HSP90, and HSP110. By maintaining cellular homeostasis and promoting stress tolerance, HSPs act as vital guardians in helping chickens cope with HS and its associated consequences. The review synthesized relevant literature to shed light on the importance of HSPs in stress adaptation, cellular homeostasis, and the maintenance of normal cell metabolism in chickens. The adverse effects of HS on chickens include oxidative stress and compromised immune systems, making them more susceptible to infections. So also, HS negatively affects production performance and meat quality in poultry. Understanding the functions of HSPs in chickens offers valuable insights into stress adaptation and health, and could potentially lead to the identification of HSP biomarkers, genetic selection for heat tolerance, investigations into the interplay between HSPs and immune function, and the development of nutritional interventions to enhance HSP activity. By exploring these potential research directions, the review aimed to contribute to the development of novel approaches to mitigate the negative effects of HS on poultry, ultimately improving productivity and animal welfare in a changing climate.

Impact of chronic heat stress on behavior, oxidative status and meat quality traits of fast-growing broiler chickens

This research aimed to investigate, through a multifactorial approach, the relationship among some in-vivo parameters (i.e., behavior and blood traits) in broilers exposed to chronic HS, and their implications on proximate composition, technological properties, and oxidative stability of breast meat. A total of 300 Ross 308 male chickens were exposed, from 35 to 41 days of age, to either thermoneutral conditions (TNT group: 20°C; six replicates of 25 birds/each) or elevated ambient temperature (HS group: 24 h/d at 30°C; six replicates of 25 birds/each). In order to deal with thermal stress, HS chickens firstly varied the frequency of some behaviors that are normally expressed also in physiological conditions (i.e., increasing "drinking" and decreasing "feeding") and then exhibited a behavioral pattern finalized at dissipating heat, primarily represented by "roosting," "panting" and "elevating wings." Such modifications become evident when the temperature reached 25°C, while the behavioral frequencies tended to stabilize at 27°C with no further substantial changes over the 6 days of thermal challenge. The multifactorial approach highlighted that these behavioral changes were associated with oxidative and inflammatory status as indicated by lower blood γ-tocopherol and higher carbonyls level (0.38 vs. 0.18 nmol/mL, and 2.39 vs. 7.19 nmol/mg proteins, respectively for TNT and HS; p < 0.001). HS affected breast meat quality by reducing the moisture:protein ratio (3.17 vs. 3.01, respectively for TNT and HS; p < 0.05) as well as the muscular acidification (ultimate pH = 5.81 vs. 6.00, respectively; p < 0.01), resulting in meat with higher holding capacity and tenderness. HS conditions reduced thiobarbituric acid reactive substances (TBARS) concentration in the breast meat while increased protein oxidation. Overall results evidenced a dynamic response of broiler chickens to HS exposure that induced behavioral and physiological modifications strictly linked to alterations of blood parameters and meat quality characteristics.

Stress Factors and Their Effects on Productivity in Sheep

Products obtained from sheep have an economically important place in the world. Their adaptability to different climatic conditions, their ease of care and feeding, their high utilization of poor pasture areas with low yield and quality, the ease of flock management, their high twinning rate, and their short intergenerational period are some of the advantages of sheep production. Sheep production has the ability to adapt better to environmental stress factors, as can be understood from the presence of sheep in different geographical regions at a global level. However, the changes in environmental conditions and production cause some negative results in animals. All these negative results expose animals to various stress factors (heat, cold, transport, treatment, nutritional, shearing, weaning, etc.). All stress factors that directly and indirectly affect sheep production ultimately lead to compromised performance, decreased productivity, increased mortality, and adverse effects on the immune system. In order to cope with the current stress parameters in animals and to achieve optimum production, a holistic approach is needed according to the environmental conditions and available resources. It is important to consider the factors involved in these responses in order to manage these processes correctly and to develop adequate strategies and improve sheep welfare. This review aimed to reveal the importance of some stress factors in sheep and their effects on sheep productivity.

Physicochemical Properties, Antioxidant Markers, and Meat Quality as Affected by Heat Stress: A Review

Heat stress is one of the most stressful events in livestock life, negatively impacting animal health, productivity, and product quality. Moreover, the negative impact of heat stress on animal product quality has recently attracted increasing public awareness and concern. The purpose of this review is to discuss the effects of heat stress on the quality and the physicochemical component of meat in ruminants, pigs, rabbits, and poultry. Based on PRISMA guidelines, research articles were identified, screened, and summarized based on inclusion criteria for heat stress on meat safety and quality. Data were obtained from the Web of Science. Many studies reported the increased incidences of heat stress on animal welfare and meat quality. Although heat stress impacts can be variable depending on the severity and duration, the exposure of animals to heat stress (HS) can affect meat quality. Recent studies have shown that HS not only causes physiological and metabolic disturbances in living animals but also alters the rate and extent of glycolysis in postmortem muscles, resulting in changes in pH values that affect carcasses and meat. It has been shown to have a plausible effect on quality and antioxidant activity. Acute heat stress just before slaughter stimulates muscle glycogenolysis and can result in pale, tender, and exudative (PSE) meat characterized by low water-holding capacity (WHC). The enzymatic antioxidants such as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) act by scavenging both intracellular and extracellular superoxide radicals and preventing the lipid peroxidation of the plasma membrane. Therefore, understanding and controlling environmental conditions is crucial to successful animal production and product safety. The objective of this review was to investigate the effects of HS on meat quality and antioxidant status.

Transcriptome and metabolome analyses reveal the regulatory effects of compound probiotics on cecal metabolism in heat-stressed broilers

The effect of compound probiotics on the caecum of broilers under heat stress was assessed in this study. A total of 400 twenty-eight-day-old AA male broilers were randomly divided into 4 treatment groups, where each group had 5 replicates of 20 broilers. The 4 treatment groups were a heat stress control group (broilers receiving a normal diet) and groups HP I, HP II, and HP Ⅲ, consisting of broilers receiving 1, 5, and 10 g of compound probiotics added to each kilogram of feed, respectively. Compound probiotics (L. casei, L. acidophilus, and B. lactis at a ratio of 1:1:2) were used to formulate a compound probiotic powder, with 1 × 10¹⁰ CFU/g of effective viable bacteria. Heat stress treatment was performed at 32 ± 1°C from 9:00 to 17:00 every day from 28 d to 42 d. In d 28 to 42, compared with the HC group, the ADG of broilers in the HP II and III groups was significantly increased (P < 0.05); the ADFI difference between groups was not significant (P > 0.05); the FCR of HP II and III broilers was significantly decreased (P < 0.05); and the FCR of the HP I group increased, but the difference was not significant (P > 0.05). Transcriptome results demonstrate that 665 differential genes were screened (DEGs; upregulated: 366, downregulated: 299). The DEGs were enriched in the B cell receptor signaling pathway, the intestinal immune network for IgA synthesis, the Fc epsilon RI signaling pathway, and other signaling pathways, according to KEGG enrichment analysis. Metabolome analysis identified 92 differential metabolites (DAMs; upregulated: 48, downregulated: 44). KEGG enrichment analysis indicated significant enrichment of Pantothenate and CoA biosynthesis and beta-Alanine metabolism. The combined transcriptome and metabolome analysis revealed that the DAMs and DEGs were mostly involved in beta-alanine metabolism, arginine biosynthesis, amino sugar and nucleotide sugar, and alanine, aspartate, and glutamate metabolism. The results of this study suggest that the addition of compound probiotics has a positive effect on intestinal metabolites, improving the growth performance and contributing to the overall health of broilers under heat stress.

Effects of Stocking Density on Growth Performance, Antioxidant Status, and Meat Quality of Finisher Broiler Chickens under High Temperature

Environmental factors such as stocking density and high temperature can cause oxidative stress and negatively affect the physiological status and meat quality of broiler chickens. Here, we evaluated the effects of heat stress on the growth performance, antioxidant levels, and meat quality of broilers under different stocking densities. A total of 885 28-day-old male broilers (Ross 308) were subjected to five treatments (16, 18, 21, 23, and 26 birds/m2) and exposed to high temperatures (33 °C for 24 h) for 7 days. High stocking density (23 and 26 birds/m2) resulted in significantly decreased body weight (p < 0.01) and superoxide dismutase activity in the blood (p < 0.05) and increased (p < 0.05) rectal temperature and corticosterone. Additionally, the concentrations of heat shock protein 70 and malondialdehyde in the liver were higher in the 26 birds/m2 group (p < 0.05). Similarly, the 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity of breast meat increased linearly as the stocking density increased (p < 0.05). There was increased shear force in breast meat at low stocking density (p < 0.01). Thus, lower stocking density can relieve oxidative stress induced by high temperatures in broilers and improve the antioxidant capacity and quality of breast meat during hot seasons.

The nutritional and sensory quality of seafood in a changing climate

Climate change is impacting living marine resources, whilst concomitantly, global reliance on seafood as a source of nutrition is increasing. Here we review an emerging research frontier, identifying significant impacts of climate-driven environmental change on the nutritional and sensory quality of seafood, and implications for human health. We highlight that changing ocean temperature, pH and salinity can lead to reductions in seafood macro and micronutrients, including essential nutrients such as protein and lipids. However, the nutritional quality of seafood appears to be more resilient in taxa that inhabit naturally variable environments such as estuaries and shallow near-coastal habitats. We develop criteria for assessing confidence in categorising the nutritional quality of seafood as vulnerable or resilient to climate change. The application of this criteria to a subset of seafood nutritional studies demonstrates confidence levels are generally low and could be improved by more realistic experimental designs and research collaboration. We highlight knowledge gaps to guide future research in this emerging field.

Genome-wide scan for selection signatures and genes related to heat tolerance in domestic chickens in the tropical and temperate regions in Asia

Heat stress is one of the major environmental stressors challenging the global poultry industry. Identifying the genes responsible for heat tolerance is fundamentally important for direct breeding programs. To uncover the genetic basis underlying the ambient temperature adaptation of chickens, we analyzed a total of 59 whole genomes from indigenous chickens that inhabit South Asian tropical regions and temperate regions from Northern China. We applied F_ST and π-ratio to scan selective sweeps and identified 34 genes with a signature of positive selection in chickens from tropical regions. Several of these genes are functionally implicated in metabolism (FABP2, RAMP3, SUGCT, and TSHR) and vascular smooth muscle contractility (CAMK2), and they may be associated with adaptation to tropical regions. In particular, we found a missense mutation in thyroid-stimulating hormone receptor (41020238:G>A) that shows significant differences in allele frequency between the chicken populations of the two regions. To evaluate whether the missense mutation in TSHR could enhance the heat tolerance of chickens, we constructed segregated chicken populations and conducted heat stress experiments using homozygous mutations (AA) and wild-type (GG) chickens. We found that GG chickens exhibited significantly higher concentrations of alanine aminotransferase, lactate dehydrogenase, and creatine kinase than AA chickens under heat stress (35 ± 1°C) conditions (P < 0.05). These results suggest that TSHR (41020238:G>A) can facilitate heat tolerance and adaptation to higher ambient temperature conditions in tropical climates. Overall, our results provide potential candidate genes for molecular breeding of heat-tolerant chickens.

Impact of Heatwaves on the Physiology and Retail Meat Quality of Lambs

The experiment investigated the impact of heatwaves (HWs) on the physiology, postmortem muscle metabolism and meat quality of lambs. Seventy-two second-cross lambs (Poll Dorset × (Border Leicester × Merino)) were selected and exposed to either 1, 3 or 5 days of HWs or thermoneutal (TN) (28–38 °C and 40–60% relative humidity, RH; 18–21 °C, 40–55% RH) conditions in climate-controlled chambers. Lambs exposed to 1–5 days of a HW exhibited higher respiration rates (RRs), rectal temperatures (RTs), skin temperatures (STs) and heart rates (HRs) compared to lambs exposed to an equal duration of TN conditions. However, HWs had no significant effects on muscle metabolism (rate and extent of pH decline, muscle glycogen and lactate content) and meat quality (cooking loss and shear force). Similarly, there were limited impacts of 1–5 days of HW on the colour (L*, a*, b* and R630/580) and drip loss of the longissimus thoracis et lumborum (LTL) and semimembranosus (SM) muscles for 4 days’ overwrap retail display. Results suggest that short-duration HWs (1–5 days) had significant negative effects on animal physiology but had no effect on the muscle metabolism and meat quality.

Effects of Selenium as a Dietary Source on Performance, Inflammation, Cell Damage, and Reproduction of Livestock Induced by Heat Stress: A Review

Heat stress as a result of global warming has harmful consequences for livestock and is thus becoming an urgent issue for animal husbandry worldwide. Ruminants, growing pigs, and poultry are very susceptible to heat stress because of their fast growth, rapid metabolism, high production levels, and sensitivity to temperature. Heat stress compromises the efficiency of animal husbandry by affecting performance, gastrointestinal health, reproductive physiology, and causing cell damage. Selenium (Se) is an essential nutritional trace element for livestock production, which acts as a structural component in at least 25 selenoproteins (SELs); it is involved in thyroid hormone synthesis, and plays a key role in the antioxidant defense system. Dietary Se supplementation has been confirmed to support gastrointestinal health, production performance, and reproductive physiology under conditions of heat stress. The underlying mechanisms include the regulation of nutrient digestibility influenced by gastrointestinal microorganisms, antioxidant status, and immunocompetence. Moreover, heat stress damage to the gastrointestinal and mammary barrier is closely related to cell physiological functions, such as the fluidity and stability of cellular membranes, and the inhibition of receptors as well as transmembrane transport protein function. Se also plays an important role in inhibiting cell apoptosis and reducing cell inflammatory response induced by heat stress. This review highlights the progress of research regarding the dietary supplementation of Se in the mitigation of heat stress, addressing its mechanism and explaining the effect of Se on cell damage caused by heat stress, in order to provide a theoretical reference for the use of Se to mitigate heat stress in livestock.

Effects of methionine as free amino acid and dipeptide on productive efficiency and meat quality of broilers under acute and chronic heat stress

Context Methionine in the form of free amino acid has been widely studied in broilers challenged by heat stress (HS). However, the effects of methionine dipeptide in broilers subjected to HS are not known. Aims To evaluate the effects of methionine as free amino acid and dipeptide on the performance, oxidative status, plasma parameters and meat quality of broilers subjected to acute and chronic HS. Methods Broilers were evaluated at the following three experimental periods: 24 h of evaluation (21–22 days of age); 10 days of evaluation (22–32 days of age); and 20 days of evaluation (22–42 days of age). Broilers were divided into two groups; one group was raised in thermal comfort, and the other group was raised in continuous HS of 30°C. In both groups, animals received a diet without methionine supplementation (MD), with supplementation of methionine as free amino acid (dl-M), and with supplementation of methionine as dipeptide (dl-MM). Key results HS reduced body weight gain after 10 and 20 days of evaluation. Broilers under HS condition fed the MD diet had the highest concentrations of thiobarbituric acid reactive substances (TBARS) at 22 days of age and carbonylated proteins (CP) at 32 days of age. At 42 days of age, broilers fed the MD diet had higher concentrations of TBARS and CP. At 32 days of age, broilers under HS had lower high-density lipoprotein and higher low-density lipoprotein concentrations. In breast meat, broilers in thermal comfort fed the dl-M or dl-MM diets had a lower cooking loss. Broilers in HS fed the dl-M diet had the lowest cooking loss. HS reduced the pH of the meat of legs. Conclusions The acute and chronic HS affect the broiler performance in different ways. Methionine supplementation contributes to reduce the effects of HS. There were no notable differences between the supplementation of dl-M or dl-MM. Implications Productivity and the quality of the chicken meat are the most important attributes of the production. The ambient temperature can influence these parameters. The methionine in its most varied forms, due to its direct and indirect antioxidant function, has been shown to be an effective source of protection for the animal in adverse conditions such as during HS.

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.

Meta-analysis to predict the effects of temperature stress on meat quality of poultry

Temperature stress (TS) is a significant issue in poultry production, which has implications for animal health and welfare, productivity, and industry profitability. Temperature stress, including both hot (heat stress) and cold conditions (cold stress), is associated with increased incidence of meat quality defects such as pale, soft, and exudative (PSE) and dark, firm, and dry (DFD) meat costing poultry industries millions of dollars annually. A meta-analysis was conducted to determine the effect of ambient TS on meat quality parameters of poultry. Forty-eight publications which met specific criteria for inclusion were identified through a systematic literature review. Temperature stress was defined by extracting 2 descriptors for each treatment mean from the chosen studies: (1) temperature imposed for the experimental treatments (°C) and duration of temperature exposure. Treatment duration was categorized for analysis into acute (≤24 h) or chronic (>24 h) treatments. Meat quality parameters considered were color (L*-a*-b* scheme), pH (initial and ultimate), drip loss, cooking loss, and shear force. Linear mixed model analysis, including study as a random effect, was used to determine the effect of treatment temperature and duration on meat quality. Model evaluation was conducted by performing a k-fold cross-validation to estimate test error, and via assessment of the root mean square prediction error (RMSPE), and concordance correlation coefficient (CCC). Across both acute and chronic durations, treatment temperature was found to have a significant effect on all studied meat quality parameters. As treatment temperature increased, meat demonstrated characteristics of PSE meat and, as temperature decreased, meat demonstrated characteristics of DFD meat. The interaction between treatment temperature and duration was significant for most traits, however, the relative impact of treatment duration on the studied traits was inconsistent. Acute TS had a larger effect than chronic TS on ultimate pH, and chronic stress had a more considerable impact on color traits (L* and a*). This meta-analysis quantifies the effect of ambient TS on poultry meat quality. However, quantitative effects were generally small, and therefore may or may not be of practical significance from a processing perspective.

Hydroxy Selenomethionine Improves Meat Quality through Optimal Skeletal Metabolism and Functions of Selenoproteins of Pigs under Chronic Heat Stress

Chronic heat stress (CHS) induces metabolic changes in skeletal muscle from growth to maintenance that jeopardizes growth performance, carcass traits, and meat quality of pigs. We investigated the protective effect of dietary organic selenium (hydroxy-4-methylselenobutanoic acid, OH-SeMet) on CHS-induced skeletal muscle damages of growing pigs, and the corresponding responses of selenoproteins. A total of 40 ((Landrace ×Yorkshire) × Duroc) pigs with an average live weight of 49.64 ± 2.48 kg were used in this 4-week trial. Pigs were randomly allotted to 5 groups: The control group was raised on a basal diet in a thermoneutral environment (22 ± 2 °C); and four CHS groups were raised on a basal diet and supplemented with Se 0.0, 0.2, 0.4, and 0.6 mg/kg as OH-SeMet, respectively, in hyperthermal condition (33 ± 2 °C). CHS resulted in significant decrease of growth performance, carcass traits, and meat quality, which were associated with reduced (p < 0.05) serum alkaline phosphatase (ALP) and total superoxide dismutase (T-SOD) and increased (p < 0.05) serum creatine (CK), sarcous heat shock protein 70 (HSP70), glucokinase (GCK), phosphoenolpyruvate carboxykinase (PEPCK), and malondialdehyde (MDA) contents. Meanwhile, four metabolism-related genes and seven selenoprotein encoding genes were abnormally expressed in skeletal muscle. Dietary OH-SeMet addition partially alleviated the negative impact of CHS on carcass traits and improved meat quality. These improvements were accompanied by the increase in Se deposition, the anti-oxidative capacity of serum and muscle, and protein abundance of GPX1, GPX3, GPX4, and SELENOP. Supplementation with 0.6 mg Se/kg (OH-SeMet) restored the sarcous PEPCK, and 0.4 and 0.6 mg Se/kg (OH-SeMet) restored all abnormally expressed metabolism-related and selenoprotein encoding genes. In summary, dietary supplementation with OH-SeMet beyond Se requirement mitigated CHS-induced depression of carcass traits and meat quality of pigs associated with optimal skeletal metabolism, enhanced antioxidant capacity, and regulation of selenoproteins in skeletal muscle of pigs.

Seasons affect the phosphorylation of pork sarcoplasmic proteins related to meat quality

OBJECTIVE

Sarcoplasmic proteins include proteins that play critical roles in biological processes of living organisms. How seasons influence biological processes and meat quality of postmortem muscles through the regulation of protein phosphorylation remain to be investigated. In this study, the phosphorylation of sarcoplasmic proteins in pork longissimus muscle was investigated in four seasons.

METHODS

Sarcoplasmic proteins were extracted from 40 pork carcasses (10 for each season) and analyzed through ProQ Diamond staining for phosphorylation labeling and Sypro Ruby staining for total protein labeling. The pH of muscle, contents of glycogen and ATP were measured at 45 min, 3 h, and 9 h postmortem and the water (P2b, P21, and P22) was measured at 3 h and 9 h.

RESULTS

A total of 21 bands were detected. Band 8 (heat shock cognate 71 kDa protein; heat shock 70 kDa protein 1B) had higher phosphorylation level in summer than that in other seasons at 45 min postmortem. The phosphorylation levels of 3 Bands were significantly different between fast and normal pH decline groups (p<0.05). The phosphorylation levels of 4 bands showed negative associations with immobilized water (P21) and positive association with free water (P22).

CONCLUSION

The phosphorylation levels of sarcoplasmic proteins involved in energy metabolism and heat stress response at early postmortem time differed depending on the seasons. These proteins include heat shock protein 70, pyruvate kinase, phosphoglucomutase-1, glucose-6-phosphate isomerase, and carbonic anhydrase 3. High temperatures in summer might result in the phosphorylation of those proteins, leading to pH decline and low water holding capacity.

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.

Poultry Response to Heat Stress: Its Physiological, Metabolic, and Genetic Implications on Meat Production and Quality Including Strategies to Improve Broiler Production in a Warming World

The continuous increase in poultry production over the last decades to meet the high growing demand and provide food security has attracted much concern due to the recent negative impacts of the most challenging environmental stressor, heat stress (HS), on birds. The poultry industry has responded by adopting different environmental strategies such as the use of environmentally controlled sheds and modern ventilation systems. However, such strategies are not long-term solutions and it cost so much for farmers to practice. The detrimental effects of HS include the reduction in growth, deterioration of meat quality as it reduces water-holding capacity, pH and increases drip loss in meat consequently changing the normal color, taste and texture of chicken meat. HS causes poor meat quality by impairing protein synthesis and augmenting undesirable fat in meat. Studies previously conducted show that HS negatively affects the skeletal muscle growth and development by changing its effects on myogenic regulatory factors, insulin growth factor-1, and heat-shock proteins. The focus of this article is in 3-fold: (1) to identify the mechanism of heat stress that causes meat production and quality loss in chicken; (2) to discuss the physiological, metabolic and genetic changes triggered by HS causing setback to the world poultry industry; (3) to identify the research gaps to be addressed in future studies.

Impact of heat stress on the growth performance and retail meat quality of 2nd cross (Poll Dorset × (Border Leicester × Merino)) and Dorper lambs

The present study investigated the impact of heat stress and genetics on lamb growth performance and meat quality. Forty-eight Dorper and 2nd cross [Poll Dorset × (Border Leicester × Merino)] lambs (38--42 kg; 4-5 months old) were allocated to either thermoneutral [TN; 18-21 °C, 45-55% relative humidity (RH)], or heat stress (HS; 28 °C-38 °C, 40-60% RH) conditions in a 2 × 2 factorial design for 2 weeks. Compared with 2nd cross, Dorper lambs had a lower respiration rate (RR) and rectal temperature (RT), and exhibited less decline in body weight under HS. 2nd cross lambs showed a higher body weight gain than Dorpers under TN conditions. HS increased a* and chroma of the Longissimus thoracis et lumborum (LTL) from 2nd cross lambs over 10 days of display, but had no impact on Dorper LTL. In conclusion, Dorpers showed higher heat tolerance compared with 2nd cross lambs during the 2 weeks HS.

Effect of dietary concentrate content on feed intake, feed efficiency, and meat quality of Holstein steers fattened in a hot environment

The objective of this study was to investigate the effect of feeding high and low concentrate diets on feed intake and feed efficiency, the morphological characteristics of the rumen papillae, and meat quality of Holstein steers fattened under hot climate conditions in Oman. Ten male Holstein calves, of 5 months of age, were selected for the experiment. The animals were fed concentrate and Rhodes grass hay and were divided into two groups of high concentrate (HC, n = 5) and low concentrate diets (LC, n = 5), in which their feed intake, weight gain, and feed efficiency were evaluated across three growing periods. Feed intake and efficiency and average daily gain (ADG) of the HC group were significantly greater than for the LC group and were affected by the diet (p < .01) and the period (p < .001). Across the fattening periods, ADG declined in both groups, with ADG improved by 35% for steers on the HC diet compared to steers on the LC diet. Carcass meat quality was not affected significantly by the dietary concentrate level. In conclusion, our results can be used to make improvements in feed efficiency of Holstein steers under hot climate conditions.

Effects of protein posttranslational modifications on meat quality: A review

Meat quality plays an important role in the purchase decision of consumers, affecting producers and retailers. The formation mechanisms determining meat quality are intricate, as several endogenous and exogenous factors contribute during antemortem and postmortem periods. Abundant research has been performed on meat quality; however, unexpected variation in meat quality remains an issue in the meat industry. Protein posttranslational modifications (PTMs) regulate structures and functions of proteins in living tissues, and recent reports confirmed their importance in meat quality. The objective of this review was to provide a summary of the research on the effects of PTMs on meat quality. The effects of four common PTMs, namely, protein phosphorylation, acetylation, S-nitrosylation, and ubiquitination, on meat quality were discussed, with emphasis on the effects of protein phosphorylation on meat tenderness, color, and water holding capacity. The mechanisms and factors that may affect the function of protein phosphorylation are also discussed. The current research confirms that meat quality traits are regulated by multiple PTMs. Cross talk between different PTMs and interactions of PTMs with postmortem biochemical processes need to be explored to improve our understanding on factors affecting meat quality.

The effects of season on health, welfare, and carcass and meat quality of slaughter pigs

This study assessed the effects of season on health, behaviour, physiological stress parameters, and carcass and meat quality in a total of 480 slaughter pigs. The following health indicators were recorded: pneumonia, pleurisy, milk spots, and pericarditis. Behaviour was monitored during unloading (slipping, falling, turning back, reluctance to move, panting, shivering) and lairaging (panting, shivering, huddling). Blood lactate and glucose concentrations were determined at exsanguination. Performance indices (live weight, daily weight gain), carcass (carcass weight, backfat and loin thickness, lean meat content, carcass lesion score), and meat quality (pH, temperature, drip, thawing and cooking losses, colour, marbling) traits were measured postmortem. Pigs slaughtered in winter had the highest live weight, carcass weight, loin thickness, and carcass lesion score, while the lowest live weight, carcass weight, and backfat thickness were recorded in pigs slaughtered in summer. The highest lactate and glucose concentrations were recorded in pigs slaughtered in summer. The highest prevalence of red, soft, and exudative meat was recorded in pigs slaughtered in winter. Pigs slaughtered in summer had the lowest pH, the highest thawing loss, L* value, b* value, and occurrence of pale, soft, and exudative meat. Pigs slaughtered in autumn had the lowest drip loss, cooking loss, L* value, b* value, and the greatest percentage of red, firm, and nonexudative meat. In conclusion, the summer and winter temperatures compromised health and welfare and reduced carcass and meat quality in slaughter pigs, indicating that protection against heat and cold stress is not yet effective.

The effect of a finishing diet supplemented with γ-aminobutyric acids on carcass characteristics and meat quality of Hanwoo steers

OBJECTIVE

This study was conducted to investigate the effects of supplementation with rumen-protected γ-aminobutyric acid (GABA) on carcass characteristics and meat quality of Hanwoo steers.

METHODS

Eighteen Hanwoo steers with an average initial weight of 644.83±12.91 kg were randomly allocated into three different groups. Each group consisted of 6 animals that were treated with different diets formulated based on the animals' body weights. The control (C) group was fed a basal diet consisting of concentrate and rice straw with 74% total digestible nutrients (TDNs) and 12% crude protein (CP). The two other groups were treatment groups; one group was fed a basal diet (74% TDNs and 12% CP) supplemented with rumen-protected GABA at a dose of 150 mg/kg feed, and the other group was fed a basal diet (74% TDNs and 12% CP) supplemented with GABA at a dose of 300 mg/kg feed.

RESULTS

The GABA supplementation significantly contributed to better growth performance (p<0.05), especially the weight gain and average daily gain. It also contributed to the lower cooking loss (p<0.05), improvements in essential antioxidant enzymes and stable regulation of antioxidant activities in the longissimus lumborum of Hanwoo steers, as represented by the lower formation of malondialdehyde content within the meat, the inhibition of myoglobin oxidation indicated by the retention of the oxymyoglobin percentage, and the suppression of metmyoglobin percentage during cold storage (p<0.05).

CONCLUSION

Higher doses of GABA may not significantly promote better animal performance and meat quality, suggesting that dietary supplementation with GABA at a dose of 100 ppm is sufficient to improve the meat quality of Hanwoo steers.

Impacts of heat stress on meat quality and strategies for amelioration: a review

During the summer, high ambient temperature and humidity cause economic loss to the global livestock industry via reduced livestock productivity and increased mortality. The problem of heat stress (HS) is likely to be exacerbated by global warming and climate change. Recent research has shown that HS not only leads to physiological and metabolic perturbations in live animals but can also affect carcass and meat quality characteristics plausibly by altering the rate and extent of postmortem muscle glycolysis and resultant pH. However, these impacts of HS are not consistent across species. Higher incidence of pale soft and exudative (PSE) meat has been reported in poultry. On the contrary, higher incidence of high ultimate pH and dark firm and dry (DFD) meat or no impacts of HS have been reported in sheep and cattle. With the limited data on HS impacts on meat quality of ruminants, it is difficult to explain the exact mechanisms driving these variable impacts. However, it is hypothesized that the severity and duration of HS may lead to variable impacts due to lack of opportunity to adapdate to acute heat exposure. Longer HS exposure may allow ruminants to adapdate to heat and may not record any negative impacts on meat quality. This paper reviews the recent research on impacts of HS on meat quality characteristics and identify the key areas of further research required to better understand these negative impacts to develop strategies for amelioration. In addition, some mitigation strategies of HS have also been discussed which include both managemental and nutritional interventions.

Effect of Sex and Breed on HSPA1A, Blood Stress Indicators and Meat Quality of Lambs

The objective of this study was to examine sex and breed effects on heat shock protein 70 (HSPA1A), blood stress indicators and meat quality attributes of lambs. A hundred male and female lambs from the Dorper (n = 50) and Merino (n = 50) breeds were used in this study. Breed and sex had a significant (p < 0.05) effect on the levels of plasma HSPA1A and lactate; where the Merino lambs had higher levels than Dorper. The female lambs had higher levels of plasma HSPA1A than male lambs. Significant sex and breed interactions (p < 0.05) on the levels of plasma HSPA1A were seen. Females had higher (p < 0.05) pHu than males. Dorper lambs had higher (p < 0.05) pH₄₅, meat lightness, thawing loss and tougher meat the Merino breed. Significant correlations were found amongst plasma stress indicators and meat quality attributes. The results indicate that female lambs were more stressed by the pre-slaughter period than males, while the Merino had a higher physiological stress response compared to the Dorper. However, the Dorper breed produced tougher meat.

Heat stress impacts on broiler performance: a systematic review and meta-analysis

Heat stress (HS) is a major problem in poultry business which affects chickens' performance and may trigger large economic losses. This study intends to analyze the impact of HS on broiler chickens' performance compared with those under normal condition. A literature search was performed on PubMed, Web of Science, and Cochrane Library for studies published in English up to January 17, 2020. Outcomes of body weight gain (BWG), feed intake (FI), feed conversion ratio (FCR), and mortality were calculated by weighted difference (WMD) or odds ratio (OR) with 95% confidence interval (CI). A total of 12 studies with 470 broiler chickens were included. HS significantly decreased FI (11 trials: WMD = -97.95, 95% CI: -141.70, -54.20) and BWG (7 trials: WMD = -151.40, 95% CI: -198.59, -104.21) and significantly increased FCR (9 trials: WMD = 0.17, 95% CI: 0.04, 0.29) and mortality (8 trials: OR = 3.74, 95% CI: 1.39, 10.12) compared with the control. In conclusion, HS significantly affected broiler chickens' BWG, FI, FCR, and mortality, indicating the importance to control housing temperature to avoid unnecessary costs.

Proteomic study of hypothalamus in pigs exposed to heat stress

Background

With evidence of warming climates, it is important to understand the effects of heat stress in farm animals in order to minimize production losses. Studying the changes in the brain proteome induced by heat stress may aid in understanding how heat stress affects brain function. The hypothalamus is a critical region in the brain that controls the pituitary gland, which is responsible for the secretion of several important hormones. In this study, we examined the hypothalamic protein profile of 10 pigs (15 ± 1 kg body weight), with five subjected to heat stress (35 ± 1 °C; relative humidity = 90%) and five acting as controls (28 ± 3 °C; RH = 90%).

Result

The isobaric tags for relative and absolute quantification (iTRAQ) analysis of the hypothalamus identified 1710 peptides corresponding to 360 proteins, including 295 differentially expressed proteins (DEPs), 148 of which were up-regulated and 147 down-regulated, in heat-stressed animals. The Ingenuity Pathway Analysis (IPA) software predicted 30 canonical pathways, four functional groups, and four regulatory networks of interest. The DEPs were mainly concentrated in the cytoskeleton of the pig hypothalamus during heat stress.

Conclusions

In this study, heat stress significantly increased the body temperature and reduced daily gain of body weight in pigs. Furthermore, we identified 295 differentially expressed proteins, 147 of which were down-regulated and 148 up-regulated in hypothalamus of heat stressed pigs. The IPA showed that the DEPs identified in the study are involved in cell death and survival, cellular assembly and organization, and cellular function and maintenance, in relation to neurological disease, metabolic disease, immunological disease, inflammatory disease, and inflammatory response. We hypothesize that a malfunction of the hypothalamus may destroy the host physical and immune function, resulting in decreased growth performance and immunosuppression in heat stressed pigs.

Lighting programs as an appliance to improve growing New Zealand white rabbit's performance

Lighting regimes are possibly used as a strategy to improve rabbit production in tropical regions; on this background, this study was conducted to assess the possible role of different light (L):dark (D) regimes in improving growing New Zealand white rabbit's performance. Sixty-four growing rabbits were randomly divided into four groups. Rabbits of the first group (C) were exposed to 12 h of light (from 10.00 to 22.00 h). Rabbits of the second group (T1) were exposed to 12 h of light (from 22.00 to 10.00 h). The third group (T2) was exposed to 8 h of light (from 10.00 to 18.00 h), while the fourth group (T3) was exposed to 8 h of light (from 22.00 to 06.00 h). Temperature-humidity index values ranged between 27.00 and 28.87, indicating exposure of growing rabbits to very severe heat stress. Body weight (BW), body weight gain (BWG), feed consumption (FC), feed conversion ratio (FCR), carcass traits, blood parameters, and some physiological (rectum temperature, respiration rate) and health aspects (morbidity, mortality, and health risks %) were investigated. Rabbits of T1 showed the highest (P < 0.05) averages of BW and BWG in comparison with their counterparts. There were no significant differences in FC; however, rabbits of T1 had the lowest value of FCR at marketing. The percentages of dressed carcass, liver, and kidney in T1 and T3 were the highest. Non-significant changes were observed among the groups in most of the metabolic and hematology parameters of blood, except for ALT and N/L ratio. Further, rabbits of T1 showed the lowest rectal temperature and respiration rate in comparison with their counterparts. Conclusively, the utilization of photoperiod of afternoon program for over a short period of time in rabbitry brought in beneficial effects on growth performance and other productive and physiological parameters of growing rabbits.

Perceptions and exposure to climate events along agricultural value chains: Evidence from Nigeria

Africa's food systems are among the most vulnerable sectors to climate risk. Unfortunately, numerous activities along food supply chains (production, processing, storage, marketing and consumption) are also important contributors to climate change. Despite the differential effect of climate events on activities along food supply chains and vice versa, most climate change perception studies in agriculture focus on producers, particularly crop farmers. This study adopts a value chain perspective to examine climate change perceptions among economic agents all along the maize-poultry value chain in Nigeria. We find that economic agents perceive those climate events that have a direct effect on their economic activity and this is not restricted to crop farmers. We also find that very few actors along the maize-poultry value chain believe that their economic activity negatively affects the environment and contributes to climate change. Though African countries might currently not be major contributors to climate change, this indicates a need for more awareness among economic agents about the effects of various agriculture-related activities on the environment and their contributions to climate change to encourage practices and technologies that can reduce agriculture's negative effect on the environment and contribution to climate change.

Meat consumption: Which are the current global risks? A review of recent (2010-2020) evidences

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Consumption of fatty meats may increase risks of cardiovascular diseases and cancer.

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Production of red meats increases greenhouse gases (GHG) emissions contributing to the global warming.

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Consumption of wild meats can pose some serious risks of transmission of viruses from animals to humans.

Meat consumption has been increasing since the 1960s, but especially from the 1980s decade to today. Although meat means an important source of nutrients, it is also evident that a great consumption of this source of proteins has also a negative environmental impact. Livestock production does not only have a negative influence on GHG emissions, but also on the water footprint, water pollution, and water scarcity. With respect to human health, in 2015 the International Agency for Research on Cancer (IARC) stated that red meat was a probable carcinogen to humans (Group 2A), while consumption of processed meat was carcinogenic to humans (Group 1). Most environmental contaminants (PCDD/Fs, PCBs, PBDEs, PCNs, etc.) that are frequently found in meats are highly soluble in fats. Therefore, avoiding ingesting fats from red meats and meat products, doubtless would help in the prevention, not only of the well-known cardiovascular diseases derived of fats consumption, but also of certain kinds of cancers, mainly colorectal cancer. On the other hand, consumption of meat – especially wild meat – is related to virus infections, as many viruses have been found in wild meat trade markets. Based on the scientific literature here reviewed, we have noted that the results of the investigations conducted after the statement of the IARC, have corroborated the recommendation of reducing significantly the consumption of red meats and meat products. In turn, the reduction of meat consumption should contribute to the reduction of GHG emissions and their considerable impact on global warming and climate change. It seems evident that human dietary habits regarding meat consumption in general, and red meats and wild meats in particular, should be significantly modified downward, as much and as soon as possible.

Effects of heat stress on growth performance, selected physiological and immunological parameters, caecal microflora, and meat quality in two broiler strains

OBJECTIVE

This study was conducted to investigate the effects of normal and heat stress environments on growth performance and, selected physiological and immunological parameters, caecal microflora and meat quality in Cobb 500 and Ross 308 broilers.

METHODS

One-hundred-and-twenty male broiler chicks from each strain (one-day-old) were randomly assigned in groups of 10 to 24 battery cages. Ambient temperature on day (d) 1 was set at 32°C and gradually reduced to 23°C on d 21. From d 22 to 35, equal numbers of birds from each strain were exposed to a temperature of either 23°C throughout (normal) or 34°C for 6 h (heat stress).

RESULTS

From d 1 to 21, strain had no effect (p>0.05) on feed intake (FI), body weight gain (BWG), or the feed conversion ratio (FCR). Except for creatine kinase, no strain×temperature interactions were observed for all the parameters measured. Regardless of strain, heat exposure significantly (p<0.05) reduced FI and BWG (d 22 to 35 and 1 to 35), immunoglobulin Y (IgY) and IgM, while increased FCR (d 22 to 35 and 1 to 35) and serum levels of glucose and acute phase proteins (APPs). Regardless of temperature, the Ross 308 birds had significantly (p<0.05) lower IgA and higher finisher and overall BWG compared to Cobb 500.

CONCLUSION

The present study suggests that the detrimental effects of heat stress are consistent across commercial broiler strains because there were no significant strain×temperature interactions for growth performance, serum APPs and immunoglobulin responses, meat quality, and ceacal microflora population.

Effect of Glutamine on Antioxidant Capacity and Lipid Peroxidation in the Breast Muscle of Heat-stressed Broilers via Antioxidant Genes and HSP70 Pathway

This study investigated whether Glutamine (Gln) could be used as an additive to improve antioxidant capacity in the breast muscle of heat-stressed broilers. Two hundred and forty 22-day-old Arbor Acres broilers in the G1, G2, G3, and G4 groups (n = 60 each) were housed in a cyclic hot environment and fed the basal diet with 0%, 0.5%, 1.0%, and 1.5% Gln, respectively. Compared with the G1 group, dietary 1.5% Gln increased (p < 0.05) pH and b* values, but decreased (p < 0.05) L* cooking loss, drip loss, and water loss rate in breast meat of heat-stressed broilers. Malondialdehyde levels in the breast muscle were lower (p < 0.05) in 1.0% and 1.5% Gln groups than that of the heat-stress group. Compared with the G1 group, dietary 1.5% Gln increased (p < 0.05) catalase (CAT), glutathione, glutathione peroxidase (GSH-Px,) and total antioxidant capacity in the breast muscle of heat-stressed broilers. Furthermore, the CAT, GSH-Px, HSP70 mRNA expression levels, and HSP70 protein expression levels were increased (p < 0.05) in the G3 and G4 groups compared with the G1 group. In sum, Gln alleviated antioxidant capacity and lipid peroxidation in the breast muscle of heat-stressed broilers through antioxidant genes and HSP70 pathways.

Meat quality traits of European quails reared under different conditions of temperature and air velocity

This study’s objective was to evaluate the influence of thermal environment and air velocity during the rearing phase on European quail meat quality traits. A total of 1,152 one-day-old European quail chicks were placed inside floor pens within environmental chambers. Each experimental period was approximately 5 wks, with birds slaughtered at 37 d of age. The experimental design consisted of a 2 × 4 factorial arrangement of treatments in completely randomized design with 2 air velocities (0 and 2 m/s) × 4 air temperatures (severe cold [SC], moderate cold, thermal comfort, and moderate heat [MH]). ANOVA, with air velocity and thermal environment as fixed effects, was performed to evaluate the effect of main factors and their interaction on meat quality traits, using the GLM procedure (SAS 9.4). Least square means of treatments effects were compared using Tukey’s test (α = 0.05). Lightness (L∗), redness (a∗), and yellowness (b∗), of quail meat were affected by thermal environment and air velocity (P < 0.05). Initial and final L∗ values were greater for MH (P < 0.05). Meat from birds subjected to 2 m/s air velocity had lower final L∗, but no velocity effect was noted for initial L∗. Quail meat from SC presented higher initial and final a∗ values compared with the other thermal environment groups (P ≤ 0.001). Final a∗ was affected by air velocity (P < 0.05). Initial and final b∗ values for meat from MH were greater, 13.8 and 15.2, respectively, differing from the other treatment environments (P < 0.05). However, air velocity did not influence b∗ values (P > 0.05). Interactions were not significant for pHu (P = 0.993). Thawing loss and shear force were affected by treatments (P < 0.05) but not ultimate pH, drip loss, or sarcomere length. This study demonstrates that thermal environments and air velocity affect quail meat quality traits. Further investigation is recommended to explore effects of air velocity and thermal environment on muscle proteolysis of quail meat quality.

Influence of Long-Distance Transportation Under Various Crating Densities on Broiler Meat Quality During Hot and Humid Weather

The objective of the study was to investigate the effect of transportation distance and crating density on broiler meat quality during hot and humid weather. Breast meat samples were collected from broilers (Ross-308) after transportation for 80, 160, and 240 km at crating densities of 10, 12, and 15 birds per crate. The broilers were transported in plastic crates of 0.91 × 0.55 × 0.31 m (length × width × height) in summer at an ambient temperature of 27.2–33.6°C and relative humidity of 52.7–62.9%. The birds were then slaughtered, and the meats' physicochemical characteristics, marination and cooking attributes were measured. Meat pH at 2 hours (h) postmortem (PM) was significantly higher in birds transported for 80 and 160 km compared to those transported for up to 240 km, while meat pH at 24 h PM was higher in birds transported for up to 160 km compared to the other treatments; however, no effect of different crating densities on meat pH and drip loss was observed. Meat losses such as drip loss, thaw loss, cooking loss in raw and marinated breast, and meat shear force were significantly higher in birds transported for up to 240 km compared to the other treatments. An increase in crating density above 12 birds per crate also increased thaw loss, whereas crating density of 12 birds per crate and higher increased cooking loss and meat shear force. Meat lightness also increased significantly with the increase in transportation distance above 160 km and crating density above 12 birds per crate. In conclusion, transportation of broilers for more than 80 km with crating density higher than 12 birds per crate during summer was associated with severe losses in yield and deterioration in physical appearance and functional characteristics of meat.

Glutamine improves heat stress-induced oxidative damage in the broiler thigh muscle by activating the nuclear factor erythroid 2-related 2/Kelch-like ECH-associated protein 1 signaling pathway

The aim of the present study was to evaluate the effect of glutamine (Gln) on modulating heat stress–induced oxidative damage in the broiler thigh muscle through nuclear factor erythroid 2–related 2/Kelch-like ECH-associated protein 1 (Nrf2-Keap1) pathway. Three-hundred 22-day-old Arbor Acres broilers were reallocated into 5 groups: a control group (24 °C) fed with basal diet and 4 heat stress (HS) groups (34 °C for 8 h/D) fed with basal diet containing 0, 0.5, 1.0, and 1.5% Gln. This experiment lasted 21 D. Heat stress decreased (P < 0.05) pH, redness, and Gln levels, and increased (P < 0.05) luminance, water loss rate, and cooking loss (CL) values of the thigh meat. Compared with the HS group, supplementation with 1.5% Gln increased (P < 0.05) pH, redness, and Gln levels, but decreased (P < 0.05) luminance and CL values in the thigh meat. There were significant decreases (P < 0.05) in glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), total antioxidant capacity (T-AOC), and Nrf2 levels, but significant increases (P < 0.05) in the malondialdehyde (MDA) and Keap1 levels of the thigh muscle after HS treatment. Compared with the HS group, supplementation with 1.0, and 1.5% Gln decreased (P < 0.05) MDA and Keap1 levels; supplementation with 1.5% Gln increased (P < 0.05) GSH, GSH-Px, T-AOC, CAT, SOD, and Nrf2 levels in the thigh muscle of heat-stressed broilers. Furthermore, HS decreased (P < 0.05) Nrf2, SOD, CAT, and GSH-Px mRNA expression levels, but increased (P < 0.05) Keap1 mRNA level in the thigh muscle of broiler. Dietary supplementation with 1.5% Gln increased (P < 0.05) Nrf2, GSH-Px, CAT, and SOD mRNA expression levels, but decreased (P < 0.05) Keap1 mRNA level in the thigh muscle of heat-stressed broilers. In conclusion, dietary Gln improved the resistance of heat-stressed broiler muscles to oxidative damage possibly through reversing the muscle Gln level and inducing the expression of the Nrf2-Keap1 pathway.

Effects of heat stress on animal physiology, metabolism, and meat quality: A review

Heat stress is one of the most stressful events in the life of livestock with harmful consequences for animal health, productivity and product quality. Ruminants, pigs and poultry are susceptible to heat stress due to their rapid metabolic rate and growth, high level of production, and species-specific characteristics such as rumen fermentation, sweating impairment, and skin insulation. Acute heat stress immediately before slaughter stimulates muscle glycogenolysis and can result in pale, soft and exudative (PSE) meat characterized by low water holding capacity (WHC). By contrast, animals subjected to chronic heat stress, have reduced muscle glycogen stores resulting in dark, firm and dry (DFD) meat with high ultimate pH and high WHC. Furthermore, heat stress leads to oxidative stress, lipid and protein oxidation, and reduced shelf life and food safety due to bacterial growth and shedding. This review discusses the scientific evidence regarding the effects of heat stress on livestock physiology and metabolism, and their consequences for meat quality and safety.

GROWTH AND DEVELOPMENT SYMPOSIUM: STEM AND PROGENITOR CELLS IN ANIMAL GROWTH: The regulation of beef quality by resident progenitor cells1

The intramuscular adipose tissue deposition in the skeletal muscle of beef cattle is a highly desired trait essential for high-quality beef. In contrast, the excessive accumulation of crosslinked collagen in intramuscular connective tissue contributes to beef toughness. Recent studies revealed that adipose tissue and connective tissue share an embryonic origin in mice and may be derived from a common immediate bipotent precursor in mice and humans. Having the same linkages in the development of adipose tissue and connective tissue in beef, the lineage commitment and differentiation of progenitor cells giving rise to these tissues may directly affect beef quality. It has been shown that these processes are regulated by some key transcription regulators and are subjective to epigenetic modifications such as DNA methylation, histone modifications, and microRNAs. Continued exploration of relevant regulatory pathways is very important for the identification of mechanisms influencing meat quality and the development of proper management strategies for beef quality improvement.

Integrative analysis of long noncoding RNA and mRNA reveals candidate lncRNAs responsible for meat quality at different physiological stages in Gushi chicken

Long noncoding RNAs (lncRNAs) play important roles in transcriptional and posttranscriptional regulation. However, the effects of lncRNAs on the meat quality of chicken hasn’t been elucidated clearly yet. Gushi chickens are popular in China because of their superior meat quality, particularly the tender flesh, and unique flavor. Gushi chickens are popular in China because of their superior meat quality, delicate flesh, and unique flavor. We performed RNA-Seq analysis of breast muscle from Gushi chicken at two physiological stages, including juvenile (G20W) and laying (G55W). In total, 186 lncRNAs and 881 mRNAs were differentially expressed between G20W and G55W (fold change ≥ 2.0, P < 0.05). Among them, 131 lncRNAs presented upregulated and 55 were downregulated. We identified the cis and trans target genes of the differentially expressed lncRNAs, and constructed lncRNA-mRNA interaction networks. The results showed that differentially expressed mRNAs and lncRNAs were mainly involved in ECM-receptor interaction, glycerophospholipid metabolism, ubiquitin-mediated proteolysis, and the biosynthesis of amino acids. In summary, our study utilized RNA-seq analysis to predict the functions of lncRNA on chicken meat quality. Furthermore, comprehensive analysis identified lncRNAs and their target genes, which may contribute to a better understanding of the molecular mechanisms underlying in poultry meat quality and provide a theoretical basis for further research.

Chronic heat stress affects muscle hypertrophy, muscle protein synthesis and uptake of amino acid in broilers via insulin like growth factor-mammalian target of rapamycin signal pathway

Heat stress markedly impairs the growth performance of broilers, such as the reduction of breast muscle mass and yield. The aim of this study was to examine the molecular mechanism of depressed muscle mass and yield caused by heat stress. A total of 144 (28-day-old) male broilers were allocated randomly into 3 treatment groups: (1) the normal control group (environment temperature was 22°C), (2) the heat stress group (environment temperature was 32°C), (3) the pair-fed group (environment temperature was 22°C and pair-fed to heat stress group). The experiment lasted for 14 d (from the age of 28 to 42 d). After 14 d of heat exposure, heat stress decreased (P < 0.05) broiler average daily gain, breast muscle mass, and muscle yield, and increased (P < 0.05) feed to gain ratio. After 14 d of heat exposure, heat stress increased (P < 0.05) the activities of aspartate aminotransferase and the concentrations of uric acid and most amino acids in serum, and reduced (P < 0.05) the concentration of insulin like growth factor 1 (IGF-1) in serum. Additionally, heat stress decreased (P < 0.05) the mRNA expressions of IGF-1, IGF-1 receptor, insulin receptor substrate 1, mammalian target of rapamycin (mTOR), the 70 kD ribosomal protein S6 kinase, myogenic differentiation, myogenin, solute carrier family 38 member 2, solute carrier family 7 member 5, and solute carrier family 3 member 2 of the breast muscle. In conclusion, chronic heat stress resulted in lower breast muscle mass and yield, and decreased muscle protein synthesis and amino acid transportation by downregulating IGFs-mTOR signal pathway. These findings have important practical significance in discovering effective means to alleviate muscle loss caused by chronic heat stress.

Stress Effects on Meat Quality: A Mechanistic Perspective

Stress inevitably occurs from the farm to abattoir in modern livestock husbandry. The effects of stress on the behavioral and physiological status and ultimate meat quality have been well documented. However, reports on the mechanism of stress effects on physiological and biochemical changes and their consequent effects on meat quality attributes have been somewhat disjointed and limited. Furthermore, the causes of variability in meat quality traits among different animal species, muscle fibers within an animal, and even positions within a piece of meat in response to stress are still not entirely clear. This review 1st summarizes the primary stress factors, including heat stress, preslaughter handling stress, oxidative stress, and other stress factors affecting animal welfare; carcass quality; and eating quality. This review further delineates potential stress-induced pathways or mediators, including AMP-activated protein kinase-mediated energy metabolism, crosstalk among calcium signaling pathways and reactive oxygen species, protein modification, apoptosis, calpain and cathepsin proteolytic systems, and heat shock proteins that exert effects that cause biochemical changes during the early postmortem period and affect the subsequent meat quality. To obtain meat of high quality, further studies are needed to unravel the intricate mechanisms involving the aforementioned signaling pathways or mediators and their crosstalk.

An evaluation of environmental, intrinsic and pre- and post-slaughter risk factors associated to dark-cutting beef in a Federal Inspected Type slaughter plant

The objective was to determine the risk factors associated to dark-cutting in bovine carcasses. The study was conducted at a Federal Inspection abattoir located in northeastern Mexico. A random sample of 394 animals at slaughter was used. A total of 26 explanatory variables were evaluated; the analysis included environmental, animal-specific, and management factors both at pre- and post- slaughter periods. Only four variables were statistically significant within the final logistic regression model (P < .001). The frequency of dark-cutting carcasses was 13.45%. Lairage time was directly proportional to the percentage of risk for dark-cutting beef. Improper desensitization also increased the frequency of carcasses with this anomaly. Backfat thickness and the 24-h pH differential of the carcasses were inversely proportional to the risk for dark-cutting beef. An interesting finding was that risk factors for DFD meat are present in all stages of the slaughter process and thus to effectively address this problem an integral evaluation is needed throughout the slaughter process.

Impacts of selenium and vitamin E supplementation on mRNA of heat shock proteins, selenoproteins and antioxidants in broilers exposed to high temperature

The study was carried out to investigate the effect of dietary selenium (Se) and vitamin E (VE) supplementation on mRNA level of heat shock proteins, selenoproteins, and antioxidant enzyme activities in the breast meat of broilers under summer heat stress conditions. A total of 200 male broilers (Ross 308) of 1 day age were randomly separated into 4 groups in a complete randomized design and were given a basal diet (Control, 0.08 mg Se/kg diet) or basal diet supplemented with VE (250 mg/kg VE), sodium selenite (0.2 mg/kg Se), or Se + VE (0.2 mg/kg Se + 250 mg/kg VE) to investigate the expression of key antioxidant and heat shock protein (HSP) genes under high temperature stress. Dietary Se, VE and Se + VE significantly enhanced the activities and mRNA levels of catalase as well as superoxide dismutase (SOD) but decreased the mRNA levels of HSP70 and HSP90. Se alone or combined with VE increased the concentration of selenoprotein P and selenoproteins mRNA level and decreased the expression of HSP60. In addition, Se and Se + VE significantly enhanced the glutathione peroxidase (GPx) activity and the expression of GPx1 and GPx4 in breast muscle tissues. It is noteworthy that all the treatments significantly decreased malondialdehyde (MDA) level in the breast meat. Overall results showed that Se in combination with VE has maximal effects to mitigate heat stress. Based on given results it can be recommended that Se + VE are a suitable dietary supplement for broilers to ameliorate the negative effects of summer heat stress conditions.

Proteomic changes of the porcine skeletal muscle in response to chronic heat stress

BACKGROUND

Heat stress (HS) has an adverse effect on meat quality; however, the underlying molecular mechanisms altering meat quality due to muscle responses to stress remain unclear. Sixteen castrated male crossbreeds between Landrace × Yorkshire sows and Duroc boars (79.00 ± 1.50 kg body weight) were exposed to either thermal neutral (22 °C, n = 8) or HS (30 °C, n = 8) conditions for 3 weeks. Subsequently, the longissimus dorsi (LD) muscle of all pigs was assayed for meat quality parameters and proteome analysis.

RESULTS

HS decreased post mortem (24 h) pH and intramuscular fat, changed ultimate L*, a* and b* values and increased drip loss and shear force. Proteome analysis of the LD was conducted by two-dimensional gel electrophoresis and mass spectrometry. A total of 23 differentially expressed proteins were identified, of which three were verified by western blotting analysis. The identified proteins were involved in six types of biological process: carbohydrate metabolism, myofibrillar and cytoskeleton structure, stress response, antioxidant and detoxification, calcium binding and cellular apoptosis. Interestingly, HS induced higher levels of heat shock protein, antioxidants and calcium binding proteins, which are involved in the mechanisms of defense and homeostasis.

CONCLUSION

The results indicate that HS-induced changes in the expression of myofibrillar proteins, glucose and energy metabolism-related proteins, heat shock protein and antioxidant enzymes might, at least partly, contribute to increase in meat tenderness. These findings will provide the foundation for developing future mitigating solutions and preventative therapies to reduce the detrimental effects of chronic HS on muscle function, metabolism and meat quality. © 2017 Society of Chemical Industry.