Abstract in English:

ABSTRACT Studying the molecular mechanism of light regulation in goose reproduction can provide an important reference for domestic goose breeding. In this study, 2720 geese (first 18 weeks 2720, last 13 weeks 255) were divided into 12-h and 13-h light groups. The entire egg laying process was recorded and blood samples were taken at three times. The transcriptome was analysed on day 150. The results showed that melatonin and oestradiol increased gradually. On day 150, 17 genes were differentially expressed in the hypothalamus, pituitary and ovary. At this time, gonadotrophin-releasing hormone (GnRH) in the blood directly or indirectly inhibited the expression of GnRH in the pituitary and ovaries. The high oestradiol concentration in the blood suppressed the expression of neuropeptide Y in the hypothalamus, pituitary, and ovary tissues, and promoted the differentiation of ciliated epithelial cells in the oviduct. This study may provide a reference for light regulation of reproduction in poultry.

Abstract in English:

ABSTRACT Numerous alternative methods have already been evaluated to avoid the side effects of chemical insecticides for pest control, including plant extracts with insecticidal potential. This research aimed to evaluate the insecticidal potential (using the degree of lethality (DL%) as the parameter) of different plant extracts: timbó root (Derris urucu), neem (Azadirachta indica), cinnamon (Cinnamomum verum), garlic (Allium sativum), Persicaria lapathifolia, pyroligneous extract, neem+andiroba, and azadirachtin concentrate. For comparison, negative control (water) and commercial positive control, Termidil 200 SC (imidacloprid) were used. Statistical analysis demonstrated the existence of three distinct groups in terms of their efficiency in controlling red mites in laying hens. The group with the highest efficiency (DL>80) includes the alcoholic extract of timbó (86.10%), neem essential oil (84.20%), neem+andiroba in combination (85.36%), and Azadirachtin concentrate (81.06%). The medium efficiency group (80<DL<60) comprised Persicaria lapathifolia (66.79%), and cinnamon (61.81%); while the low efficiency group (DL<50) included garlic (44.60%), pyroligneous extract (43.10%) and the positive control (38.50%). Based on these results, alcoholic extract of Timbó root, Neem essential oil, Neem + Andiroba in combination and Azadirachtin concentrated extract are recommended, due to their DL>80%. Garlic and pyroligneous extracts as well as chemical insecticides are not recommended due to their low efficiency. Moreover, it was demonstrated that there is the possibility of resistance against commercial chemical insecticide due to its continuous use on the farm where the insects were collected. Persicaria lapathifolia and cinnamon can be used, but their efficiency is between 60-80%.

Abstract in English:

ABSTRACT (1) Background: Vaccine programs have been failing to provide complete immunity against the Newcastle disease virus (NDV). This study examines the immunological responses to the live LaSota and Avinew (VG/GA) vaccines given through spray or drinking water to broiler chickens; (2) Methods: The experimental vaccination included one unvaccinated control group and four other groups of the same size. There were three duplicates, each with 30 birds, with each group amounting to ninety birds. In addition to the status of the cellular and humoral immunity, we examined the weights and histology of the bursa and spleen; (3) Results: The bursa weight index (BWI) significantly increased on days 28 and 42 in the vaccinated groups, regardless of the vaccination method (p≤0.05). The spleen weight index (SWI) significantly increased on day 42 in VG/GA vaccinated birds, and on day 28 in chicks vaccinated with the LaSota strain (p≤0.05). T cell proliferation in response to stimulation with PHA was significantly higher across all vaccinated groups compared to the unvaccinated ones. Serum IgG was significantly elevated on days 21, 28, and 42 post-vaccination with VG/GA or LaSota strain for both vaccination routes (p≤0.05); (4) Conclusions: The data generated from this study demonstrated that significant immune responses can be generated with the two examined Newcastle vaccine strains using the spray and drinking water vaccination routes.

Abstract in English:

ABSTRACT The aim of this work was to study the growth performance, gastrointestinal tract traits, and cecal short chain fatty acid (SCFA) concentration in response to insoluble fiber in two broiler strains from 0 to 42 days of age. The experiment had a completely randomized design (CRD) with four treatments and four replicates (17 birds per replicate) arranged as a 2 × 2 factorial with two broiler strains (Ross 308 vs. Cobb 500) and two processed wheat straw (PWS) levels (0 vs. 3%). Average daily feed intake (ADFI) (p<0.0001), and body weight gain (BWG) (p=0.0025) were greater and feed conversion ratio (FCR) (p<0.0001) was poorer in Cobb than in Ross birds from 0 to 21 days of age. In contrast, higher BWG was observed in the Ross birds from 22 to 42 days of age (p=0.0448). Processed wheat straw did not affect performance from 0 to 21 days; however, BWG was lower from 22 to 42 days of age (p=0.0098). The concentration of acetate (p<0.0001), propionate (p<0.0001) and butyrate (p=0.0063) in the cecum was higher in Ross birds fed with PWS. Overall, broiler strains responded similarly to dietary insoluble fiber. Moreover, the inclusion of PWS had no negative effect on carcass yield at marketing weight, while also improving gastrointestinal tract development and cecal SCFA concentration.

Abstract in English:

ABSTRACT Mathematical models based on regression equations are an important tool for the interpretation of data generated by the serological monitoring of poultry flocks. The present study aimed to evaluate the serological monitoring of breeders and commercial laying hens by several poultry companies, and to develop mathematical models for seven different poultry diseases. Data from serological tests for seven diseases (chicken infectious anemia, infectious bronchitis, infectious bursal disease, Newcastle disease, avian encephalomyelitis, avian metapneumovirus, and avian reovirus) were selected for analysis in this study. The variables “age of birds at the time of blood collection” was considered as the independent variable (x), while “antibody titer” was set as the dependent variable (y). Analysis of variance and coefficient of multiple determination (R²) were used to select the model with the highest capacity to adequately describe the analyzed data. Data from serological monitoring generated 166 linear and non-linear regression equations, but only 1.2% of them yielded an R²≥0.8 and more than 25 serum collections. The low number of suitable models may be related to the lack of standardization of the sample collection. In summary, serological monitoring of breeders and commercial laying hen flocks can be performed using mathematical models, but the lack of standardization of sample collections may have led to limited results.

Abstract in English:

ABSTRACT Avian coccidiosis, caused by Eimeria protozoan parasites, inflicts significant economic losses to the poultry industry. The host-species specificity and the resilient nature of Eimeria oocysts demand efficient prophylactic and therapeutic management programs. To enhance control strategies, several metric indices are used to measure the level of coccidial infection, but serious challenges exist in their applicability and interpretation in commercial settings. A combination of lesion scores (LS) and direct micro-quantification of E. maxima oocyst (Micro-q Em) in the broiler gastrointestinal tract offers a comprehensive approach to understanding the population dynamics of Eimeria species during the broiler rearing period (RP). One hundred and three integrated broiler companies in various states of Brazil over a ten-year period (2012-2022) were sampled, in a longitudinal study that included 8,423 broiler chicks aged from 14 to 42 days. The results indicated differences in Eimeria sp. LS and Micro-q Em incidence throughout the RP. E. acervulina exhibited a prevalence of 56.4%, E. maxima 28.0%, and E. tenella 15.6%. The LS of E. maxima showed an unexpected peak of incidence at the beginning and end stages of the RP, while the LS of E. acervulina displayed a prevalence in the epidemiological coccidiosis curve after 32 days of age, suggesting an extraordinary dynamic oocysts reproduction. A very strong correlation (0.958) was observed between the LS of Eimeria sp. and Micro-q Em scoring. This monitoring strategy offered useful information for the accurate incidence analysis of Eimeria species throughout the RP. These findings help optimize control methods for unexpected outbreaks of Eimeria infections at the farm level in Brazil.

Abstract in English:

ABSTRACT The study evaluated the efficacy of a bioproduct based on andiroba oil (BBAO) applied to eggs stored with or without treatment, at room temperature or refrigerated for up to 35 days. The product’s impact on physical quality, bacteriological concentrations, chemical composition, and lipid oxidation of yolks was analyzed. The results showed that eggs treated with the BBAO maintained better physical quality, with lower water loss and lower lipid oxidation compared to untreated eggs. Refrigerated storage further enhanced preservation, resulting in higher albumen contents and lower microbial contamination. Eggs stored without the bioproduct at room temperature exhibited higher bacterial growth, including Salmonella spp., which was absent in treated and refrigerated eggs. The findings suggest that combining the BBAO with refrigeration extends the shelf life of eggs by protecting against microbial contamination and oxidative degradation, offering a sustainable method to improve egg quality, particularly in regions with limited access to refrigeration.

Abstract in English:

ABSTRACT This study evaluates the effectiveness of machine learning algorithms in predicting quail egg quality based on nine key parameters, including egg weight, egg width, egg length, yolk height, yolk width, yolk weight, albumen height, albumen width, and albumen length. A dataset comprising 350 eggs from 18-week-old Japanese quails was analyzed using Logistic Regression, Naive Bayes, Support Vector Machines, k-Nearest Neighbors, Random Forest, and Gradient Boosting. The findings revealed that models combining internal and external quality parameters achieved significantly higher accuracy compared to models based solely on external attributes. Notably, Random Forest and Gradient Boosting algorithms achieved accuracies exceeding 97%, while predictions based only on external parameters exhibited lower accuracy but presented a promising starting point for non-invasive evaluations. This study strongly highlights the applicability and flexibility of machine learning in evaluating quail egg quality. The ability of algorithms to integrate various quality parameters and analyze complex relationships provides both rapid and scalable solutions. These findings demonstrate that machine learning technologies have the potential to drive innovative approaches in the poultry industry and inspire future research focusing on larger datasets and additional parameters to further enhance accuracy.

Abstract in English:

ABSTRACT Reproductive efficiency is a cornerstone of success in poultry production, particularly in species such as the Japanese quail (Coturnix coturnix japonica), which are valued for their high productivity and adaptability. Semen extenders have been evaluated for their efficacy in preserving sperm quality and improving reproductive outcomes. This study assessed the effects of different semen extenders on the reproductive performance of Japanese quail, focusing on key parameters such as fertility, hatchability, and semen quality. Over a period of twenty-eight days, a total of 300 adult female breeder quails (5 to 6 weeks of age) with an average weight of 200 ± 8 g were divided into four experimental groups, under a completely randomized design. The treatment groups included T1 (proctodeal gland foam), T2 (quail egg albumen), T3 (Shit’s extenders), and T4 (control group with undiluted semen). Each group comprised five replicates with 15 birds per replicate. Additionally, 75 male breeder quails with an average weight of 170 ± 7 g were housed separately for semen collection and analysis. The results showed that birds in the T1 group, treated with proctodeal gland foam as a semen extender, exhibited the highest fertility and hatchability rates. This group also displayed improved semen quality, with increased sperm motility and a higher percentage of live sperm count. These findings suggest that proctodeal gland foam is an effective semen extender for enhancing reproductive outcomes in Japanese quails.

Abstract in English:

ABSTRACT This study investigated the effect of cuticle thickness on quality traits of eggs stored at different conditions for varying durations. Eggs were obtained from Lohmann LSL Classic layer chicken hybrids housed in enriched cage system. 450 eggs were analyzed, 90 eggs at each storage period; 0, 14, and 28 days (d) at ~4 °C and ~24 °C, respectively. Additionally, after 0, 14, and 28 d of storage, eggs were stained with a 1% aqueous solution of Edicol Supra Pea Green H and Tartrazin. Cuticle thickness was determined using a colorimeter, and then egg quality analyses were performed. The results showed a decrease in egg weight, specific gravity, albumen height, albumen index, Haugh unit, yolk height, yolk index, and yolk color score, and an increase in egg weight loss rate with the increase in storage duration (p<0.05; p<0.01). Eggs stored at room temperature had the lowest weight, specific gravity, albumen height, albumen index, Haugh unit, yolk height, yolk index, and yolk color, and the highest egg weight loss (p<0.05; p<0.01). The opposite was true for fresh and fridge-stored eggs, whose values for most of the traits above were similar. Eggs with thinner cuticle coverage had the lowest weight, albumen height, albumen index, and Haugh unit, and the highest weight loss rate; whereas eggs with a thicker cuticle had the highest weight, albumen height, albumen index, and Haught unit (p<0.05; p<0.01). Specific gravity, yolk height, and yolk index were significantly lower in eggs with thinner cuticle coverage than in those with medium and thicker cuticle coverage; however, shell-breaking strength was significantly higher in eggs with thinner cuticle coverage compared to those with medium and thicker cuticle coverage. It was concluded that prolonged egg storage and storing eggs at room temperature results in a significant decline in the analyzed egg quality traits, with the exception of shape index and shell thickness. Also, as the egg cuticle layer becomes thicker, the rate of weight loss and shell-breaking strength are reduced, while the internal egg quality traits are preserved.

Abstract in English:

ABSTRACT The mtDNA D-loops of four chicken breeds (Betong, Khao Chang, Srivijaya Naked-Neck, and Dang) from the native chicken populations of Narathiwat province and Red jungle fowl from the southern region of Thailand were analyzed to assess their genetic diversity and genetic relationships. The 558 fragments of the mtDNA D-loop were genotyped using PCR, and 20 variation sites and 23 haplotypes were detected in 326 mtDNA D-loop sequences. The haplotype diversity and nucleotide diversity of the Red jungle fowl were 0.936 ± 0.034 and 0.00806 ± 0.00087, respectively. Thai native chicken populations had a haplotype diversity of 0.000 to 0.9050, and a nucleotide diversity of 0.00000 to 0.00856, thus revealing the high genetic diversity of the native Thai chicken breeds. Analysis of molecular variance indicated that most of the variation was within the population (78.20%). The results of the median-joining network and phylogenetic tree were consistent and revealed that Thai local chicken breeds and Red jungle fowl were divided into eight main haplogroups (A-F, H, and V). The greatest number of haplotypes was classified into haplogroup B (6 haplotypes), followed by haplogroup V (5 haplotypes). Moreover, there was no breed-specific haplogroup. These results suggest that the breeds likely originated from multiple matrilineal lines, and the mtDNA D-loops assessed in this study appear to lack breed specificity.

Abstract in English:

ABSTRACT This study investigates the use of tomato juice (TJ) to assess its effects on egg quality, laying hen performance, and various blood parameters. A total of 128 Babcock white laying hens, aged 50 weeks, were randomly divided into four groups (n=32), each consisting of four subgroups with eight hens. The experimental groups received tomato juice supplementation in their drinking water at concentrations of 0%, 1%, 2.5%, and 5% for four weeks. Fecal samples were collected on days 15 and 30 to evaluate total aerobic bacteria, Lactobacillus spp., Enterococcus spp., Salmonella spp., and Clostridium perfringens counts. The results showed that the 5% tomato juice group significantly increased egg weight (65.95 g/hen/day) and egg mass (56.52 g/hen/day) compared to the control group (62.63 g/hen/day and 45.35 g/hen/day, respectively). Additionally, the 5% TJ group showed improvements in egg quality, with a higher Haugh unit (80.77) and yolk color (11.21) compared to the control group (75.65 and 10.13, respectively). In conclusion, tomato juice supplementation positively affected laying hen performance, egg quality, and blood Vitamin E levels without adverse effects. Additionally, TJ supplementation appeared to enhance intestinal microbiota balance. These findings suggest that tomato juice, when added to drinking water at different concentrations, can improve both egg quality and intestinal health in older laying hens. Furthermore, the unchanged Enterococcus counts in the SBM agar indicate that tomato juice supplementation did not significantly impact this bacterial population, suggesting it may not affect all gut microbiota uniformly. However, the reduction in Lactobacillus spp. in the 5% TJ group suggests a selective influence on intestinal microbiota, which could be important for gut health management in laying hens.

Abstract in English:

ABSTRACT A total of 480 one-day-old straight-run broilers were used to evaluate the effects of feed form (FF), fiber source (FS), and fiber level (FL) on production performance, foregut development, gut histomorphology, apparent ileal digestibility (AID) of amino acids (AA) and cecal microbiota count. Eight experimental diets comprising 6 replicates with 10 birds each were tested in a 2 × 2 × 2 factorial arrangement in a completely randomized design using two FF (Pellet vs. Mash), two FS (Oat hulls (OH) vs. Sugarcane bagasse (SCB)) and two FL (3 vs. 5%). Overall (0-35 days), broilers fed OH pelleted diet had better (p< 0.05) feed intake, body weight gain and FCR than those fed SCB pelleted or mash diets. Broilers fed OH pelleted diet showed improved VH (villus height) by 5% and VCR (villus height to crypt depth ratio) up to 13%. An interaction (p<0.05) between FS × FF was detected for lysine, methionine, threonine, valine, arginine and cysteine. The pelleted diet decreased (p<0.05) the empty relative weight of proventriculus and gizzard. Pelleted diet containing OH increased cecal Lactobacillus spp.. and reduced E. Coli count in comparison to mash OH and SCB. In conclusion, 3% OH in pelleted diets may potentially be used in broiler diets to enhance duodenal histomorphology, nutrients digestibility, beneficial cecal microbiota count, and production performance.

Abstract in English:

ABSTRACT This study examined the critical role of image color accuracy in surveillance systems, particularly in poultry houses, using affordable video cameras. Variations in commercial camera color processing can lead to inconsistent metrics. Therefore, common cameras were evaluated on the Raspberry Pi platform, aiming to minimize color differences through a three-stage correction process. The analysis without correction revealed significant color discrepancies, particularly in the PI cameras using an automatic white balance, with differences of approximately 50. Gamma correction was applied to improve accuracy, thereby reducing the color differences to within 20 for most cameras. Polynomial regression further decreased the differences to less than 10 across various temperatures, demonstrating superior performance, especially for large initial discrepancies. Field experiments with and without color charts confirmed the effectiveness of color restoration using correction matrices. The study concluded that polynomial regression significantly enhances color accuracy on the Raspberry Pi platform, offering valuable applications across different temperatures and scenarios, thereby contributing to advancements in related fields.

Abstract in English:

ABSTRACT Assessing microbial indicators during slaughter is essential for managing risks and reducing foodborne pathogens. This study aimed to evaluate and categorize the hygienic-sanitary performance of a poultry slaughter operation through the Enterobacteriaceae count (EC) in chilled carcasses, collected every hour of production, totaling 360 samples. Process variables such as slaughter speed, carcass weight, fasting time, percentage of condemnation due to contamination, and Salmonella spp. positive batches were considered. Statistics were based on descriptive data analysis and the Generalized Estimating Equations model. There was a significant difference between the medians of the first and second production shifts (1.32 versus 2.16 log10 CFU/g); p<0.001). Process variables did not correlate with the EC; however, carcass samples from positive batches for Salmonella spp. showed a significantly higher median EC result than samples from negative batches (2.79 versus 1.61 log10 CFU/g; p<0.001). The mapping of microbiological indicators, such as Enterobacteriaceae, provides a photograph of the hygienic-sanitary conditions of the slaughterhouse. This offers the opportunity to maintain hygienic self-control of the process and ensure the quality of the products.

Abstract in English:

ABSTRACT This study aimed to evaluate the effects of different exogenous proteases in broiler diets on performance, metabolizable energy, and the crude protein (CP) digestibility values of diets. A total of 1440, 384, and 432 birds were distributed in a completely randomized design in the performance, metabolism, and digestibility experiments, respectively. The treatments applied to the three experiments were: T1 - positive control (PC; basal diet, 23,23% CP in starter phase and 20,58% CP in grower/finisher phase); T2 - negative control (NC; 18,54% CP in starter phase and 18,46% CP in grower/finisher phase); T3 - NC added with Protease A; T4 - NC added with Protease B; T5 - NC added with Protease C; T6 - NC added with Protease D; T7 - NC added with Protease E; and T8 - NC added with Protease F, plus a treatment with a protein-free diet in the digestibility experiment. Reducing the protein level in the diet reduced BWG and worsened FCR. The proteases did not improve any of the performance parameters evaluated, except for protease C, which improved BWG, but not at a sufficient level to recover the lost performance, and not equal to CP. In addition, there were no differences in the metabolizable energy values. Furthermore, the proteases did not improve the standardized ileal digestibility of crude protein of diets with reduced protein. In conclusion, the supplementation of the tested proteases does not recover the growth performance lost by reducing the crude protein in the diet.

Abstract in English:

ABSTRACT Allium tuberosum (Chinese chives; CC) contains large amounts of metabolites that have antibacterial, antioxidant, and anti-inflammatory properties. In our previous study, fermented CC was shown to improve physiological functions and have positive results in broilers. In this study, we investigated egg productivity, egg quality, blood parameters, organ and intestinal characteristics, and gut microbiota by adding solid-state fermented CC (FCC) to laying hen diets. A total of 120 laying hens (40-weeks-old) were randomly assigned to one of the three dietary treatment groups: (1) basal diet + carrier mixture (CM) 1.5% (CC juice concentration 0%; CON); (2) basal diet + 0.5% FCC + 1.0% CM (CC juice concentration 0.1%; FCC 0.1%); (3) basal diet + 1.5% FCC (CC juice concentration 0.3%; FCC 0.3%). Each treatment was designed with 10 replicates, and 4 hens were assigned to each replicate. The experiment lasted for 5 weeks. As a result, the FCC 0.1% group had a heavier egg weight, and the FCC 0.3% group had higher feed intake (p<0.05). However, feed conversion ratio (FCR) was similar in all treatments (p>0.05). Egg quality was also not observed to be affected by the supplementation of FCC (p>0.05). However, interestingly, when eggs were stored for 4 weeks, FCC treatment hens showed lower malondialdehyde (MDA) concentrations than CON (p<0.05). Although the content of blood components was similar (p>0.05), FCC 0.1% affected ileum length and potential pathogen growth (p<0.05). This study suggests that FCC as a feed additive for laying hens improves egg productivity, and storage period, and helps maintain health.

Abstract in English:

ABSTRACT This study was conducted to investigate the effects of dietary paddy rice on the performance of geese. A total of 210 28-day-old geese were randomly allotted to 5 treatment groups with 7 replicates of 6 geese each. The geese were raised for 42 days on feed with 0 (control), 30%, 40%, 50%, and 60% dietary paddy rice inclusion. The results showed that dietary paddy rice increased body weight, average daily feed intake, and average daily gain of geese (p<0.05), but did not influence feed/gain ratio (p>0.05). Increasing dietary paddy rice levels decreased the plasma total bilirubin, direct bilirubin, and indirect bilirubin content of geese (p<0.05). The percentage of carcass, half-eviscerated yield, and eviscerated yield in geese were increased as dietary paddy rice increased (p<0.05). The dietary paddy rice did not affect the breast meat quality of geese (p>0.05). In conclusion, paddy rice could increase the growth performance, and had no negative effects on plasma biochemical parameters, carcass traits, and breast meat quality of geese from 28 to 70 d of age. We showed that paddy rice can be used up to a concentration of 60% in the geese diets.

Abstract in English:

ABSTRACT This study examined the effects of the supplementation of drinking water with Taiwanese green propolis ethanolic extract (TGPE) on the growth performance, serum biochemical parameters, intestinal inflammation-associated gene expression, and fecal microbiota in pullets. One-day-old pullets were divided into (1) a control group (without TGPE supplementation) (C), (2) a low-dose group (300 µg/mL TGPE) (L), and (3) a high-dose group (600 µg/mL TGPE) (H). Chicks were provided ad libitum access to feed and water for 12 weeks. The results revealed that there was no significant difference in growth performance and blood biochemical parameters among groups. Supplementation with 600 µg/mL TGPE reduced inflammation-associated gene expression in the duodenum and ileum. TGPE supplementation (300 and 600 µg/mL) reduced α-diversity (richness and evenness) in the feces of laying hen chicks at 12 weeks of age. β-diversity confirmed that bacterial structure were well-separated at 4, 8, and 12 weeks of age. TGPE supplementation (300 and 600 µg/mL) increased the abundance of the genus Lactobacillus and reduced the abundance of the genus Escherichia-Shigella. The abundance of the genus Escherichia-Shigella was positively correlated with inflammation-associated gene expressions, whereas the abundance of the genus Lactobacillus was inversely correlated with inflammation-associated gene expression in pullets at 12 weeks of age. In conclusion, supplementing drinking water with TGPE can reduce intestinal inflammation-associated gene expression and modulate fecal microbiota in pullets. TGPE at the optimal concentration of 600 µg/mL in drinking water may have anti-inflammatory effects and modulates gut microbiota in pullets.

Abstract in English:

ABSTRACT Eggshell prevents microbial contamination of the egg’s internal content, and its quality determines the commercial acceptance or rejection of eggs. Broken eggs amount to about 6 to 8% of total egg production, resulting in economic loss to the egg industry. The task of animal genomics is the development of accurate genetic methods to identify genes that play a role in the manifestation of commercial traits. The current report aimed to systematically review literature on single nucleotide polymorphism and its association with chicken eggshell thickness. Literature used for the current study was obtained from the Google Scholar, PubMed, ScienceDirect, and Web of Science databases using single nucleotide polymorphisms, eggshell thickness, and chickens as key words combined in various ways. From the primary search, 76 articles were obtained, and 15 qualified to be used in the study after further screening for eligibility. These 15 studies were published from 2008 to 2023, and most of them originated from China (6), Japan (2) and Nigeria (2). Ovocleidin-116 (20%), Ovocalyxin-32 (13%) and ChEST985k21(13%) were mostly investigated in different chicken breeds. In conclusion, they are considered to be the best candidate genes playing a role in the development of eggshell thickness, as there was association between genotypes and eggshell thickness.