Genetic improvement of egg laying traits in Fayoumi chickens bred under conditions of heat stress through selection and gene expression studies

Early Feeding Strategy Mitigates Major Physiological Dynamics Altered by Heat Stress in Broilers

Heat stress is one of the stressors that negatively affect broiler chickens, leading to a reduction in production efficiency and profitability. This reduction affects the economy in general, especially in hot and semi-hot countries. Therefore, improving heat tolerance of broiler chicks is a key to sustained peak performance, especially under adverse environmental heat stress conditions. The present study investigated three early feed withdrawal regimes (FWD) as a potential mitigation for thermal stress exposure. A total of 240 unsexed one-day-old Cobb-500 chicks were randomly recruited to one of four experimental groups using a completely randomized design (10 birds × 6 replicates). The experimental groups included the control group with no feed withdrawal (control), while the other three groups were subjected to early feed withdrawal for either 24 h on the 5th day of age (FWD-24), 12 h on the 3rd and 5th day of age (FWD-12), or 8 h on the 3rd, 4th, and 5th day of age (FWD-8), respectively. Production performance was monitored throughout the experiment. Meanwhile, blood and liver samples were taken at the end of the experimental period to evaluate major physiological dynamic changes. Our findings demonstrated that under chronic heat stress conditions, FWD treatments significantly improved broilers' production performance and enhanced several physiological parameters compared with the control. Serum levels of thyroid hormones were elevated, whereas leptin hormone was decreased in FWD groups compared with the control. Moreover, serum total protein, globulin, and hemoglobin levels were higher, while total cholesterol and uric acid were lower in the FWD groups. Furthermore, FWD groups showed significantly higher antioxidant marker activity with a significantly lower lipid peroxidation level. Immunoglobulin levels, lysozyme, complement factor C3, and liver heat shock protein 70 (HSP70) concentration were also elevated in FWD compared with the control. Also, serum interleukin-1β (IL-1β) and interferon-gamma (IFN-γ) significantly increased with FWD. Based on our findings, early feed withdrawal can be applied as a promising non-invasive nutritional strategy for broilers reared under chronic heat stress conditions. Such a strategy promotes the alleviation of the deleterious effects of heat stress on broiler performance, immunity, and redox status, owing to the onset of physiological adaptation and the development of thermotolerance ability.

Whole genome discovery of regulatory genes responsible for the response of chicken to heat stress

Long noncoding RNAs (lncRNAs) are functional bridges connecting the genome with phenotypes by interacting with DNA, mRNA, and proteins. Using publically available acute heat stress (AHS)-related RNA-seq data, we discovered novel lncRNAs and tested their association with AHS along with ~ 8800 known lncRNAs and ~ 28,000 mRNA transcripts. Our pipeline discovered a total of 145 potentially novel-lncRNAs. One of them (Fishcomb_p-value = 0.06) along with another novel transcript (annotated as protein-coding; Fishcomb_p-value = 0.03) were identified as significantly associated with AHS. We found five known-lncRNAs and 134 mRNAs transcripts that were significantly associated with AHS. Four novel lncRNAs interact cis-regulated with 12 mRNA transcripts and are targeted by 11 miRNAs. Also six meta-lncRNAs associate with 134 meta-mRNAs through trans-acting co-expression, each targeted by 15 and 216 miRNAs, respectively. Three of the known-lncRNAs significantly co-expressed with almost 97 of the significant mRNAs (Pearson correlation p-value < 0.05). We report the mentioned three known-lncRNAs (ENSGALT00000099876, ENSGALT00000107573, and ENSGALT00000106323) as the most, significantly regulatory elements of AHS in chicken. It can be concluded that in order to alleviate the adverse effects of AHS on chicken, the manipulation of the three regulatory lncRNAs could lead to a more desirable result than the manipulation of the most significant mRNAs.

The genetic impact of heat stress on the egg production of Thai native chickens (Pradu Hang dum)

Sustainable poultry production in adverse weather conditions is a widely debated issue, which has led to research into the development of breeds of poultry that are genetically resistant to heat. This study aimed to investigate the effects of heat stress on the genetics of monthly egg production and examine the threshold point of heat stress for preventing thermal stress and its effects on chicken productivity. The data of 5,965 monthly egg production records of 629 Thai native Pradu Hang dum chickens were used for analysis in combination with the temperature-humidity index (THI) calculated by meteorological data near the testing station. The average THI throughout the year was 76.6, and the highest was 82. The THI data were subsequently used to find the threshold point of heat stress. The THI equation used in this study was chosen by its highest correlation (-0.306) between THI values and monthly egg production. At a THI of 74, the lowest -2 logL was found and was considered the threshold point of heat stress. This means that monthly egg production would start decreasing when the THI was 74. Heritability was 0.15±0.03, and genetic and permanent environmental correlations were -0.29 and -0.48, respectively. The threshold point was used to estimate the estimated breeding values (EBVs) of the monthly egg production and heat stress individually, and EBVs were calculated into the selection index. The selection index values when the animal was selected for the replacement herd for all chickens (top 50%, 30%, 20%, and 10%) were 0.14, 0.90, 1.27, 1.53, and 1.91, respectively, and the genetic progress was 0.55, 0.60, 0.68, 0.75, and 0.77, respectively. This shows that the selection index values are lower if there are many selected animals. The recommendation for animal genetic selection is that the top 10% is appropriately because it seems to be most preferred. Therefore, using a selection index for high egg production and heat tolerance in Thai native chickens is possible to achieve genetic assessment in a large population.

Heat Shock Protein Response to Stress in Poultry: A Review

Compared to other animal species, production has dramatically increased in the poultry sector. However, in intensive production systems, poultry are subjected to stress conditions that may compromise their well-being. Much like other living organisms, poultry respond to various stressors by synthesising a group of evolutionarily conserved polypeptides named heat shock proteins (HSPs) to maintain homeostasis. These proteins, as chaperones, play a pivotal role in protecting animals against stress by re-establishing normal protein conformation and, thus, cellular homeostasis. In the last few decades, many advances have been made in ascertaining the HSP response to thermal and non-thermal stressors in poultry. The present review focuses on what is currently known about the HSP response to thermal and non-thermal stressors in poultry and discusses the factors that modulate its induction and regulatory mechanisms. The development of practical strategies to alleviate the detrimental effects of environmental stresses on poultry will benefit from detailed studies that describe the mechanisms of stress resilience and enhance our understanding of the nature of heat shock signalling proteins and gene expression.

Gene expression networks and functionally enriched pathways involved in the response of domestic chicken to acute heat stress

Heat stress in poultry houses, especially in warm areas, is one of the main environmental factors that restrict the growth of broilers or laying performance of layers, suppresses the immune system, and deteriorates egg quality and feed conversion ratio. The molecular mechanisms underlying the response of chicken to acute heat stress (AHS) have not been comprehensively elucidated. Therefore, the main object of the current work was to investigate the liver gene expression profile of chickens under AHS in comparison with their corresponding control groups, using four RNA-seq datasets. The meta-analysis, GO and KEGG pathway enrichment, WGCNA, machine-learning, and eGWAS analyses were performed. The results revealed 77 meta-genes that were mainly related to protein biosynthesis, protein folding, and protein transport between cellular organelles. In other words, under AHS, the expression of genes involving in the structure of rough reticulum membrane and in the process of protein folding was adversely influenced. In addition, genes related to biological processes such as "response to unfolded proteins," "response to reticulum stress" and "ERAD pathway" were differentially regulated. We introduce here a couple of genes such as HSPA5, SSR1, SDF2L1, and SEC23B, as the most significantly differentiated under AHS, which could be used as bio-signatures of AHS. Besides the mentioned genes, the main findings of the current work may shed light to the identification of the effects of AHS on gene expression profiling of domestic chicken as well as the adaptive response of chicken to environmental stresses.

Genetic polymorphism in HSPB6 gene and their association with heat tolerance traits in Indian Karan Fries (Bos taurus x Bos indicus) cattle

Heat shock proteins (HSPs) act as a chaperone activity ensuring the folding, unfolding, and refolding of denatured proteins, which help in a protective role during thermal stress in dairy cattle. This study aimed to detect genetic variations of the HSPB6 gene and to determine their association with heat tolerance traits in Karan Fries cattle. Five single nucleotide polymorphisms (SNPs) (SNP 1-5) were reported in the Karan Fries cattle, which included three transitions viz. SNP1-g.161G > A, SNP2-g.436G > A, and SNP4-g.2152A > G and two transversions viz. SNP3-g.1743C > G, SNP5-g.2417A > T. The association analysis revealed that the three SNPs loci i.e., SNP1-g.161G > A, SNP2-g.436G > A, and SNP3-g.1743C > G were significantly (p < 0.01) associated with the respiration rate (RR) and rectal temperature (RT) (°C) traits. Furthermore, in the case of heat tolerance coefficient (HTC) trait was found significantly associated (p < 0.01) with SNPs loci i.e., SNP1-g.161G > A, SNP2-g.436G > A, and SNP3-g.1743C > G. The Hap 4 (GACAT) was found to more adaptable than cattle of other haplotypes as reflected by lower values of RR, RT and HTC. This study provides the first association analyses between the SNPs and haplotypes of HSPB6 gene and heat tolerance traits in Karan Fries cattle, which could be used as effective SNP markers in genetic selection for heat tolerance in cattle breeding program.

Welfare issues and potential solutions for laying hens in free range and organic production systems: A review based on literature and interviews

In free-range and organic production systems, hens can make choices according to their needs and desires, which is in accordance with welfare definitions. Nonetheless, health and behavioral problems are also encountered in these systems. The aim of this article was to identify welfare challenges observed in these production systems in the EU and the most promising solutions to overcome these challenges. It is based on a review of published literature and research projects complemented by interviews with experts. We selected EU specific information for welfare problems, however, the selected literature regarding solutions is global. Free range use may increase the risk of infection by some bacteria, viruses and parasites. Preventive methods include avoiding contamination thanks to biosecurity measures and strengthening animals' natural defenses against these diseases which can be based on nutritional means with new diet components such as insect-derived products, probiotics and prebiotics. Phytotherapy and aromatherapy can be used as preventive and curative medicine and vaccines as alternatives to antibiotics and pesticides. Bone quality in pullets and hens prevents keel deviations and is favored by exercise in the outdoor range. Free range use also lead to higher exposure to variable weather conditions and predators, therefore shadow, fences and guard animals can be used to prevent heat stress and predation respectively. Granting a free range provides opportunities for the expression of many behaviors and yet many hens usually stay close to the house. Providing the birds with trees, shelters or attractive plants can increase range use. Small flock sizes, early experiences of enrichment and personality traits have also been found to enhance range use. Severe feather pecking can occur in free range production systems, although flocks using the outdoor area have better plumage than indoors. While many prevention strategies are facilitated in free range systems, the influence of genetics, prenatal and nutritional factors in free range hens still need to be investigated. This review provides information about practices that have been tested or still need to be explored and this information can be used by stakeholders and researchers to help them evaluate the applicability of these solutions for welfare improvement.

Brooding Temperature Alters Yolk Sac Absorption and Affected Ovarian Development in Goslings

In order to explore the brooding temperature on the absorption of yolk sac and the ovary development of goslings, 126 1-day-old female goslings were randomly divided into three groups with three replicates in each group. The brooding temperatures were set at 32 °C, 29 °C and 26 °C (represent G32, G29 and G26), respectively, in each group. At 48, 60 and 72 h, two goslings from each replicate were weighed, and the yolk sac was collected and weighed. The fatty acid composition of yolk sac fluid was determined by gas chromatography-mass spectrometry (GC-MS). At 1, 2, 3, and 4 weeks of age, goslings from each replicate were weighed, the ovaries were weighed and fixed for hematoxylin-eosin (HE) staining, Cell cycle checkpoint kinase 1 (CHK1), fibroblast growth factor 12 (FGF12) and Sma-and Mad-related protein 4 (SMAD4) which related to regulation of ovarian development were determined by qRT-PCR. The body weight of G29 and G26 was significantly higher than that of G32 at 72 h (p < 0.05). The contents of C14:0, C16:0, C18:2n6c and total fatty acid (ΣTFA) from G32 were significantly higher than that of G26 (p < 0.05), and the contents of C18:1n9t and C22:0 in G29 were significantly higher than that of G26 (p < 0.05). The ovary index, ovary and body weight were significantly higher in G29 than those of G32 and G26 at 2 weeks of age (p < 0.05). The number of primordial follicles, number of primary follicles and diameter of primary follicles were significantly higher in G29 than those in G32 and G26 at 4 weeks of age (p < 0.05). In G29, the expression of CHK1 and SMAD4 was significantly higher than that in G32, and the expression of FGF12 and SMAD4 was significantly higher (p < 0.05) than that in G26 at 2 and 4 weeks of age. In conclusion, brooding temperature at 29 °C could promote the absorption of fatty acids in yolk sac, body weight gain, and ovarian development through up-regulating the expression of CHK1, FGF12 and SMAD4.

Identification of Key Candidate Genes in Runs of Homozygosity of the Genome of Two Chicken Breeds, Associated with Cold Adaptation

Simple Summary

The search for genomic regions related to adaptive abilities preserved in the chicken gene pool of two breeds, which have not been under intensive selection pressure, is of great importance for breeding in the future. This study aimed to identify key candidate genes associated with the adaptation of chickens to cold environments (using the example of the Russian White breed) by using molecular genetic methods. A total of 12 key genes on breed-specific ROH (runs of homozygosity) islands were identified, which may be potential candidate genes associated with the high level of adaptability of chickens to cold environments in the early postnatal period. These genes were associated with lipid metabolism, maintaining body temperature in cold environments, non-shivering thermogenesis and muscle development and are perspectives for further research.

Abstract

It is well known that the chicken gene pools have high adaptive abilities, including adaptation to cold environments. This research aimed to study the genomic distribution of runs of homozygosity (ROH) in a population of Russian White (RW) chickens as a result of selection for adaptation to cold environments in the early postnatal period, to perform a structural annotation of the discovered breed-specific regions of the genome (compared to chickens of the Amroks breed) and to suggest key candidate genes associated with the adaptation of RW chickens to cold environments. Genotyping of individual samples was performed using Illumina Chicken 60K SNP BeadChip^® chips. The search for homozygous regions by individual chromosomes was carried out using the PLINK 1.9 program and the detectRuns R package. Twelve key genes on breed-specific ROH islands were identified. They may be considered as potential candidate genes associated with the high adaptive ability of chickens in cold environments in the early postnatal period. Genes associated with lipid metabolism (SOCS3, NDUFA4, TXNRD2, IGFBP 1, IGFBP 3), maintaining body temperature in cold environments (ADIPOQ, GCGR, TRPM2), non-shivering thermogenesis (RYR2, CAMK2G, STK25) and muscle development (METTL21C) are perspectives for further research. This study contributes to our understanding of the mechanisms of adaptation to cold environments in chickens and provides a molecular basis for selection work.

Climate change and heat stress: Impact on production, reproduction and growth performance of poultry and its mitigation using genetic strategies

Heat stress is an important environmental determinant which adversely affects the performance of poultry worldwide. The present communication reviews the impact of heat stress on production, reproduction and growth performance of poultry, and its alleviation using genetic strategies. The adverse effects of high environmental temperature on poultry include decrease in growth rate, body weight, egg production, egg weight, egg quality, meat quality, semen quality, fertility and hatchability, which cause vast financial losses to the poultry industry. High ambient temperature has an antagonistic effect on performance traits of the poultry. Thus, selection of birds for high performance has increased their susceptibility to heat stress. Additionally, heat burden during transportation of birds from one place to another leads to reduced meat quality, increased mortality and welfare issues. Molecular markers are being explored nowadays to recognize the potential candidate genes related to production, reproduction and growth traits for selecting poultry birds to enhance thermo-tolerance and resistance against diseases. In conclusion, there is a critical need of formulating selection strategies based on genetic markers and exploring more genes in addition to HSP25, 70, 90, H1, RB1CC, BAG3, PDK, ID1, Na, F, dw and K responsible for thermoregulation, to improve the overall performance of poultry along with their ability to tolerate heat stress conditions.

Heat stress management in poultry

High ambient temperature is one of the major causes of economic losses in the livestock industry. The poultry industry is an integral part of the livestock industry. It faces severe losses due to heat stress (HS). The adverse effects of HS can be seen on production performance, body temperature, intestinal health, appetite hormone regulation, immune responses and oxidative characteristics. It is important to monitor these parameters to identify the HS possessions during rearing so that timely action can be taken to minimize the adverse effects of high ambient temperature. Furthermore, the application of productive methods on farms is equally important. Several strategies have been suggested by researchers. Providing a suitable environment with selective rearing systems along with proper ventilation and hygiene is the basic requirement for all types of livestock reared for animal protein. Supplementation of appropriate feed additive could be useful for improving intestinal absorption and minimizing adverse effects of HS. Selection for breeding heat resistant birds also provide merits for improving the germplasm of the strains. Early age thermal conditioning also helps in developing resistance for HS. The most recent advancement is the supplementation of active substances during incubation. It is expected that these methods may have a potential impact on the poultry industry for creating thermotolerance in the newly hatched chicks. This review highlights the major issues concerning chicken health and suggests the measures to be adopted following the increase in environmental temperature.

Emerging Genetic Tools to Investigate Molecular Pathways Related to Heat Stress in Chickens: A Review

Simple Summary

New genomic tools have been used as an instrument in order to assess the molecular pathway involved in heat stress resistance. Local chicken breeds have a better attitude to face heat stress. This review aims to summarize studies linked to chickens, heat stress, and heat shock protein.

Abstract

Chicken products are the most consumed animal-sourced foods at a global level across greatly diverse cultures, traditions, and religions. The consumption of chicken meat has increased rapidly in the past few decades and chicken meat is the main animal protein source in developing countries. Heat stress is one of the environmental factors which decreases the productive performance of poultry and meat quality. Heat stress produces the over-expression of heat shock factors and heat shock proteins in chicken tissues. Heat shock proteins regulate several molecular pathways in cells in response to stress conditions, changing the homeostasis of cells and tissues. These changes can affect the physiology of the tissue and hence the production ability of chickens. Indeed, commercial chicken strains can reach a high production level, but their body metabolism, being comparatively accelerated, has poor thermoregulation. In contrast, native backyard chickens are more adapted to the environments in which they live, with a robustness that allows them to survive and reproduce constantly. In the past few years, new molecular tools have been developed, such as RNA-Seq, Single Nucleotide Polymorphisms (SNPs), and bioinformatics approaches such as Genome-Wide Association Study (GWAS). Based on these genetic tools, many studies have detected the main pathways involved in cellular response mechanisms. In this context, it is necessary to clarify all the genetic and molecular mechanisms involved in heat stress response. Hence, this paper aims to review the ability of the new generation of genetic tools to clarify the molecular pathways associated with heat stress in chickens, offering new perspectives for the use of these findings in the animal breeding field.

Thermoregulatory, behavioral and productive responses of laying hens supplemented with different types and dosages of phytases raised in a hot environment: An integrative approach

This study had the following objectives: (i) to evaluate the thermoregulatory and behavioral responses of light laying hens supplemented with different types and dosages of phytases in the two day shifts; and (ii) to integrate the thermoregulatory and behavioral responses with performance of these birds raised in a hot environment. 270 light laying hens of the Hy-Line White lineage, with a body weight of 1.60 ± 0.092 kg were distributed in a completely randomized design in a 2 × 2 + 1 factorial model with two types of phytases (bacterial and fungal) and two dosages (450 and 900 FTU), and a control diet. The day shift (morning and afternoon) was considered as a fixed effect in the factorial arrangement. Principal component analysis (P_CA), correspondence analysis (C_A) and canonical discriminant analysis (C_DA) were used. There was no interaction (P > 0.05) between phytases and dosages for thermoregulatory responses. Respiratory rate (R_R), cloacal temperature (C_T), and surface temperature with feathers (S_TWF) and featherless (S_TF) were higher (P < 0.001) in the afternoon. Birds show different thermoregulatory and behavioral responses in the two shifts of the day. We also observed that birds supplemented with bacterial and fungal phytase showed similar thermoregulatory and behavioral responses to the control group in both day shifts. Expression of the "eating" activity was greater in the morning, while the birds remained sitting longer in the afternoon. Egg production was higher (P < 0.001) in birds supplemented with bacterial phytase. The phytase dosages had no effect on thermoregulatory, behavioral or performance responses. Egg production, feed conversion per dozen eggs corresponded to 81.1% of the differences between bacterial and fungal phytase supplementation and group control. Thus, we conclude that: (i) phytase dietary supplementation has no effect on the thermoregulatory responses of laying hens reared in a hot environment; (ii) birds supplemented with bacterial phytase showed higher egg production; and (iii) phytases (450 and 900 FTU) do not interfere with productive, behavioral and thermoregulatory responses.