Poultry, Volume 4, Issue 3 (September 2025) – 16 articles

Enterococci, commonly found in the normal intestinal flora of humans and animals, have emerged as an important human pathogen. A total of 184 isolates (88 isolates in 2015 and 96 isolates in 2016) were collected from 46 flocks. Two predominant enterococcus species were identified: Enterococcus faecalis (59%) and Enterococcus faecium (~39%). Resistance to penicillin was significantly decreased in the overall enterococci community, while it remained unchanged in the multi-class drug resistant (MDR) community. We identified the emeA and efrAB genes, which encode efflux pump systems, in 93% (26/28) of the MDR isolates with (intermediate) resistance to levofloxacin. The ermB gene was present in all MDR strains with resistance to erythromycin. The lsa gene was detected in 87% (84/97) of the MDR isolates with resistance to quinupristin/dalfopristin. About 82.2% of MDR strains in 2015 and 100% of MDR strains in 2016 carried the insertion sequence IS256, which is known to be associated with AMR genes, conferring resistance to erythromycin, gentamicin and vancomycin in enterococci. These results support the need for monitoring AMR in Gram-positive bacteria in poultry production, specifically in broiler chicken farms, to complement current AMR data, and develop a timely intervention framework. Full article

A 28-day study involving 448 male Ross 308 broilers aimed to determine the effect of dietary rice bran (RB) and xylanase (XYL) in maize- and wheat-based diets on chicken growth, N-corrected apparent metabolizable energy (AMEn), and nutrient availability. Two isonitrogenic and isocaloric maize- or wheat-based basal diets (BDs) were formulated matching breeding recommendations. Each diet was then split in four parts: two parts BD was substituted with 75 g/kg RB and then one of the RB substituted and one of the original parts was supplemented with 16,000 XYL units/kg, resulting in a total of eight experimental dietary treatments. Each diet was fed to seven pens of eight birds per pen following randomization. The data were analyzed by ANOVA using a 2 × 2 × 2 factorial design (cereal type × RB × XYL). Enzyme supplemented RB-free wheat-based diet had greater AMEn (p = 0.002) and fiber digestibility (p = 0.007) compared to the rest. Feeding RB reduced daily feed intake (p = 0.015) and weight gain (p < 0.001) of chicks. Birds fed wheat-based diets had greater feed efficiency, coupled with an increase in starch digestibility (SD) and energy conversion ratio (ECR). The observed differences in feed efficiency were explained only by SD and ECR. Full article

Newcastle Disease (ND) is an important and notable disease among the avian infectious diseases, because of its high contagiousness, and the most virulent strains of ND virus (NDV) have impacted poultry breeders all over the world. Immunization and biosecurity measures are used to reduce ND; however, vaccination has been shown to offer protection against clinical signs but not against virus proliferation and shedding, which could have an adverse effect on the environment. The genetic basis for inherent resistance to NDV has been established, and genetic selection on existing resistance-related genetic variation can help to mitigate virus propagation. Further, understanding the genes and processes that drive the response to NDV will lay the groundwork for genetic improvement in poultry. The majority of studies on NDV susceptibility make use of phenotypic indicators such as body weight, morbidity, mortality, antibody response, and viral load. According to recent advancements in molecular genetic research, many different genes are diversely regulated in different chicken lines to NDV infection, which might be used in the future to establish disease-resistant breeding approaches. It is possible that many more genes linked to illness and resistance are still to be discovered, because the precise mechanism of resistance is not entirely understood. The enhanced genetic knowledge of chickens and the development of more advanced transgenic techniques would lead to pathogen resistance. Hence, this paper summarizes the current understanding of genetic resistance to Newcastle Disease, and we additionally highlight a few possible genes/markers connected with NDV that may improve chicken resistance to NDV infections and can be used to produce NDV-resistant chicken breeds/strains in the near future. Full article

Antimicrobial resistance (AMR) constitutes a serious public health issue, and the European Union (EU) requires reduction in the sales of antibiotics in farmed animals of 50% by 2030. A scoping review was conducted in PubMed for the years from 2000 to 2024, limited to the English and German languages, with the aims to (1) provide an overview of factors on commercial poultry farms potentially associated with health-related endpoints such as mortality, disease prevalence, carcass condemnation, performance as well as AMR/antimicrobial usage at different hierarchical levels (animal, flock/batch, stable, farm), and (2) identify inconsistencies with respect to these potential risk factors. Overall, 34 peer-reviewed publications met the inclusion criteria for the review. Significant associations identified in the uni- or multivariable statistical analysis were summarised using graphs and bar charts. The results highlight that risk factor–outcome associations often are complex, inconsistent with regards to the direction of the influence especially for some ordinal or categorical variables. In some associations such as the sex of the animals and performance, contrary directions were reported in different studies—illustrating the multifactorial dynamics of commercial poultry production. This research enhances the understanding of the complexity of commercial poultry production, which is essential when designing future studies and interpreting their results. Full article

Understanding how environmental conditions affect broiler comfort across different seasons is crucial for enhancing welfare in commercial poultry production. This study aimed to identify the relationship between housing environment, litter conditions, and broiler discomfort at different growth stages using data collected from two flocks reared during winter and summer. Environmental variables (temperature, humidity, ammonia, pH, and CO₂) and broiler responses were recorded and analyzed weekly. Discomfort was defined as a binary variable based on threshold deviations in temperature and air quality. Non-parametric statistical tests and a Random Forest model were employed to explore associations and predict comfort status. Results showed that discomfort was significantly higher during winter, particularly in weeks 1 and 6, likely due to thermal instability and rising ammonia levels. Summer flocks exhibited more stable comfort profiles. The predictive model achieved a high test accuracy (97.1%) and identified broiler weight, ammonia, and temperature as the strongest predictors of discomfort. Weekly discomfort patterns and feature importance analyses revealed critical intervention points and variables. These findings provide actionable insights for automating welfare monitoring in commercial broiler production, offering valuable information for season-specific management strategies and demonstrating the potential for integrating predictive models into automated welfare monitoring systems to support precision livestock farming. Full article

Optimal commercial conditions have been shown to improve the performance and meat yield of broilers. Also, dietary 25-hydroxycholecalciferol (25OHD₃; crystalline form) has not shown a negative impact on chicken health when it was fed at 10 times (10×) higher than 69 μg/kg. The objectives of this study were to determine the effects of up to 8 times (8×) higher than the commercial level (69 μg/kg of feed) of dietary 25OHD₃ on the performance, breast meat yield, and serum 25OHD₃ concentration of broilers. Eighteen male chicks were randomly assigned to each of 20 pens within each of the two dietary treatments. Treatments were commercial diets containing 250 IU/kg of vitamin D₃ (control) for the starter [(0 to 14 days post-hatch (poh), grower (15 to 28 poh), and finisher (29 to 42 poh) dietary phases; or diets containing Hy-D (water-soluble source of 25OHD₃) that consisted of 552 (8×) μg/kg of 25OHD₃ for the starter, 276 (4×) μg/kg of 25OHD₃ for the grower, and 34.5 (0.5×) μg/kg of 25OHD₃ for the finisher dietary phases. Live performance variables as well as serum 25OHD₃ concentrations were measured in each dietary phase. At 14, 28, and 39 poh, breast meat yield that included pectoralis major (P. major) and pectoralis minor (P. minor) muscle weights was determined in ten replications per dietary treatment. Breast yield was also calculated by adding the values of the P. major and P. minor muscles. From 14 to 42 poh, the Hy-D diets decreased (p < 0.0001) broiler body weight (BW) and BW gain and increased (p < 0.0001) total mortality and feed conversion ratio in comparison to control treatment groups. In addition, birds fed Hy-D diets had significantly (p < 0.0001) lower P. major and breast meat yields from 14 to 39 poh as compared to those birds fed the control diet. Serum 25OHD₃ concentration was significantly (p < 0.0001) higher (10×) in birds that belonged to the Hy-D diet treatment than those in the control diet treatment group. These results indicate that the disproportionally high (8×) level of dietary 25OHD₃ resulted in detrimental effects on the performance and meat yield of broilers. A reduction in both performance and meat yield of broilers in response to the elevated level of dietary 25OHD₃ may have been due to vitamin D₃ toxicity, which can result in an association with the overproduction of the active form of the vitamin in response to elevated serum concentrations of 25OHD₃. Full article

To determine if exposing embryos to light during incubation affects antibody titer and corticosterone immediately following hatch, we incubated layer eggs and exposed them to light or darkness and vaccinated a subset of each treatment against Newcastle Disease Virus (NDV) using in ovo administration on ED 18, spray application at hatch (d 0), or not at all. There were six treatments: light incubated and non-vaccinated (LNV), light incubated and in ovo vaccinated (LIV), light incubated and post-hatch vaccinated (LPHV), dark incubated and non-vaccinated (DNV), dark incubated and in ovo-vaccinated (DIV), and dark incubated and post-hatch vaccinated (DPHV). Plasma corticosterone (CORT) and NDV antibody titers were measured on d 0, 7, and 14. Light-incubated chicks had lower (p < 0.05) plasma CORT on d 0. NDV titers did not differ (p > 0.05) between light- and dark-incubated chicks on d 0, 7, or 14. However, LIV chicks had higher antibody titers than LPHV on d 14. Exposing embryos to continuous green light during incubation may reduce stress during the early post-hatch period. Vaccination method, rather than exposure to continuous green light during incubation, may have a greater impact on humoral immune response post-hatch. Full article

(1) Background: The goal of the present study was to evaluate whether the supplementation with a multi-species probiotic in the diet of laying hens can change the microbiota and health status of the oviduct. (2) Methods: A total of 60 cages housing lightweight laying hens (36 weeks old) were randomly assigned to the following two different treatments: a control group fed a diet without probiotic, and a treatment group receiving diets supplemented with 50 g/ton of probiotics. The trial lasted for 26 weeks, after which five layers were slaughtered per treatment for oviduct (magnum) assessment, focusing on microbiome composition, oxidant and antioxidant status, and morphological analyses. Additionally, intestinal (jejunum) samples were collected to determine oxidant and antioxidant status. (3) Results: Probiotic supplementation resulted in lower counts of organisms from the RB41 order (p = 0.039) and Burkholderia genus (p = 0.017), and a total reduction in Bacillus and Corynebacterium (p = 0.050) compared to the control treatment. Genera Burkholderia (p = 0.017), Corynebacterium (p = 0.050), and Bacillus (p = 0.050) were also lower with the probiotic supplementation in relation to the control. Genera Epulopiscium (p = 0.089), Flavobacterium (p = 0.100), Ruminococcus (p = 0.089), and Staphylococcus (p = 0.100) tended to be lower in the probiotic group compared to the control. No significant differences were found between treatments for oviduct lesions. Probiotic treatment resulted in a higher protein thiol level in the intestine compared to the control (p < 0.001). However, the use of probiotics tended to reduce glutathione S-transferase levels in the oviduct compared to the control (p = 0.068). (4) Conclusions: These results suggest that dietary supplementation with probiotics can modulate the oviduct microbiota and improve the antioxidant status of laying hens, without causing tissue damage. Further research is warranted to explore the long-term implications of these changes on reproductive performance and egg quality. Full article

Foraging behavior in hens is an important indicator of animal welfare. It involves both the search for food and exploration of the environment, which provides necessary enrichment. In addition, it has been inversely linked to damaging behaviors such as severe feather pecking. Conventional studies rely on manual observation to investigate foraging location, duration, timing, and frequency. However, this approach is labor-intensive, time-consuming, and subject to human bias. Our study developed computer vision-based methods to automatically detect foraging hens in a cage-free research environment and compared their performance. A cage-free room was divided into four pens, two larger pens measuring 2.9 m × 2.3 m with 30 hens each and two smaller pens measuring 2.3 m × 1.8 m with 18 hens each. Cameras were positioned vertically, 2.75 m above the floor, recording the videos at 15 frames per second. Out of 4886 images, 70% were used for model training, 20% for validation, and 10% for testing. We trained multiple You Only Look Once (YOLO) object detection models from YOLOv9, YOLOv10, and YOLO11 series for 100 epochs each. All the models achieved precision, recall, and mean average precision at 0.5 intersection over union (mAP@0.5) above 75%. YOLOv9c achieved the highest precision (83.9%), YOLO11x achieved the highest recall (86.7%), and YOLO11m achieved the highest mAP@0.5 (89.5%). These results demonstrate the use of computer vision to automatically detect complex poultry behavior, such as foraging, making it more efficient. Full article

The objective of this study was to evaluate the effect of two limestone granulometries (0.568 and 1.943 mm) and different levels of vitamin D3 (12.5 g and 25 g) on the thermoregulatory and behavioral responses of replacement pullets. Lohman brown lineage pullets (270 birds), with an average weight of 639.60 g ± 6.05 and an initial age of eight weeks, were used in this study. The experimental design adopted was completely randomized in a 2 × 2 × 2 + 1 factorial arrangement (2 limestone granulometries × 2 levels of vitamin D3 × 2 shifts). The respiratory rate (RR), cloaca temperature (CT), feather surface temperature (FST) and featherless surface temperature (FLST) were higher in the afternoon (p < 0.05), while the thermal gradient (TG) was higher in the morning (p < 0.05). Birds supplemented with different limestone granulometries and different levels of vitamin D3 showed similar thermoregulatory and behavioral responses. The “eating” activity was more frequent in the morning, while in the afternoon, the birds remained seated for longer (p < 0.05). The dietary supplementation with different limestone granulometries and vitamin levels did not impair thermoregulation even at higher temperatures. Regardless of the level of vitamin D3, they showed a better expression of welfare-related behavioral activities in the morning in the semiarid region. Full article

Environmentally modified housing [EMH; windowless, insulated sidewalls and ceiling, thermostatically controlled ventilation fans) versus conventional housing [CVH; cross-ventilated, insulated ceiling, ceiling fans) improved broiler performance in the summer. The objective of this investigation was to determine whether social behaviors differed between two population densities (0.06 m²/chick [HD] or 0.07 m²/chick [LD]) in these houses. We used a randomized block statistical design, involving houses, population densities, observation times, and bird age. Behaviors were observed weekly, during the morning and the afternoon. Individual observers focused on the group of broilers in one of three defined 26.76 m² areas in each of the four pens in each house. Aggressive encounters, tail and back pecking, feather eating, thermoregulatory, preening, and flock mobility were recorded. Feather pecking, eating and aggressive encounters were expressed at greater rates in HD birds in CVH. A salt-deficient diet caused increased feather pecking and aggressive encounters, which decreased after correction of the mistake. Increased heat indices (HIs), HD, and greater light intensity in CVH influenced behaviors and mortality more severely than in EMH. In CVH and EMH, burrowing/thermoregulatory/resting activity increased with increasing HIs. Afternoon preening was elevated significantly in EMH. It was concluded that broilers reared in EMH were more comfortable and experienced improved welfare compared to those reared in CVH. Full article

Background: Reliable and non-invasive methods for assessing welfare in poultry are essential for improving evidence-based welfare monitoring and advancing management practices in commercial production systems. The iris-to-pupil (IP) ratio, previously validated by our group in primates and cattle, reflects autonomic nervous system balance and may serve as a physiological indicator of stress in laying hens. This study evaluated the utility of the IP ratio under field conditions across diverse commercial layer housing systems. Materials and Methods: In total, 296 laying hens (Lohmann Brown, n = 269; White Leghorn, n = 27) were studied across four locations in Canada housed under different systems: Guelph (indoor; pen), Spring Island (outdoor and scratch; organic), Ottawa (outdoor, indoor and scratch; free-range), and Toronto (outdoor and hobby; free-range). High-resolution photographs of the eye were taken under ambient lighting. Light intensity was measured using the light meter app. The IP ratio was calculated using NIH ImageJ software (Version 1.54p). Statistical analysis included one-way ANOVA and linear regression using GraphPad Prism (Version 5). Results: Birds housed outdoors had the highest IP ratios, followed by those in scratch systems, while indoor and pen-housed birds had the lowest IP ratios (p < 0.001). Subgroup analyses of birds in Ottawa and Spring Island farms confirmed significantly higher IP ratios in outdoor environments compared to indoor and scratch systems (p < 0.001). The IP ratio correlated weakly with ambient light intensity (r² = 0.25) and age (r² = 0.05), indicating minimal influence of these variables. Although White Leghorn hens showed lower IP ratios than Lohmann Browns, this difference was confounded by housing type; all White Leghorns were housed in pens. Thus, housing system but not breed was the primary driver of IP variation. Conclusions: The IP ratio is a robust, non-invasive physiological marker of welfare assessment in laying hens, sensitive to housing environment but minimally influenced by light or age. Its potential for integration with digital imaging technologies supports its use in scalable welfare assessment protocols. Full article

The objective of this study was to validate the energy matrix of guanidinoacetic acid (AGA) in broiler diets, assessing its effects on performance, carcass traits, organ development, and meat quality. The experiment was conducted at the UNOESC Xanxerê poultry facility using 480 COBB broilers in a completely randomized design with three treatments: positive control (standard energy level), negative control (75 kcal/kg reduction in metabolizable energy—ME), and negative control + AGA (600 mg/kg). Male broilers in the positive control and negative control + AGA groups showed improved feed conversion, higher weight gain, and greater feed intake (p < 0.001) compared to the negative control group. A significant difference in relative liver weight (p = 0.037) was observed between the positive and negative control groups. Birds supplemented with AGA had higher blood glucose levels and lower levels of cholesterol (p = 0.013), triglycerides (p = 0.005), total proteins (p < 0.001), and creatinine (p = 0.056). Regarding meat quality, the AGA-supplemented group showed higher crude protein content and greater lipid peroxidation in breast meat. In conclusion, the inclusion of AGA using an energy matrix reduced by 75 kcal/kg ME is feasible, maintaining performance and carcass characteristics while improving meat quality in broiler chickens. Full article

Nowadays, consumers are becoming increasingly concerned about the husbandry conditions under which animals are raised, particularly broilers, since broilers are one of the species whose welfare is most impaired in intensive farming systems. One of the primary means of communicating husbandry practices to consumers is through product labelling. Thus, a rising number of animal welfare labelling schemes for broilers are being developed and used across Europe by initiatives of both public and private stakeholders, including NGOs that advocate for animal welfare. This review aims to identify, analyze, and compare these labelling schemes with a focus on the main animal welfare provisions included in them, which contribute to enhanced animal welfare. The schemes were identified through web searches, so that we could visit their official websites, access their standards and regulations and study them in detail. We included in our research only those schemes whose criteria were publicly available. In total, 16 schemes were selected and analyzed. Although these schemes vary in their criteria, they all enhance the welfare standards of broiler production, primarily through incorporating environmental enrichment and/or access to the outdoors. Most schemes define and specify in detail the required animal welfare provisions, setting a clear application frame for the raising period of the birds. However, the welfare of animals during transport and slaughter is often overlooked. Full article

Stocking density is one of the major concerns in all production systems, which is why lawmakers, retailers, and consumers are increasingly concerned about this issue and its relation to animal welfare. The aim of this study was to identify if stocking density had an effect on white egg layer production, egg quality, bird health, and welfare parameters. For this study, five stocking densities were evaluated in colony cages: 1342 cm²/hen, 897 cm²/hen, 671 cm²/hen, 535 cm²/hen, and 445 cm²/hen. Egg production and physical egg quality were measured. Hen health and welfare parameters including corticosterone levels, H/L, oxidative stress pathways, jejunum tight junction protein expression, bone health, gut histology, body condition, and cytokine expression were evaluated. The results from this indicated that higher stocking densities resulted in lower production but larger eggs, while feed efficiency remained unaffected. Furthermore, physical egg quality parameters also remained unaffected. When stress and welfare parameters were analyzed, this research identified that decreasing stocking density did not affect jejunum oxidative stress pathways, pro-inflammatory cytokine expression, bone health, or intestinal health. At the final sampling period (69 weeks), the highest stocking density demonstrated higher corticosterone concentrations and IL-10 expression compared to the lowest stocking density. Furthermore, feather scores were found to be poorer as density increased. Finally, the highest density had higher Hansen’s test scores compared to other densities, which indicates a greater fear response. In conclusion, it appears that decreasing stocking density may provide some benefits in production and welfare to commercial egg layers, particularly at the end of the laying cycle. Full article

The amount of space provided to laying hens has been an animal welfare topic of concern from consumers, special interest groups, and lawmakers. The freedom to perform normal behaviors is one component of animal welfare, and, therefore, the objective of this study was to assess behavior at different stocking densities. Shaver White laying hens were housed in colony cages at five stocking densities. Video recordings of three cages/treatment were taken at 30, 46, and 62 weeks of age in the morning, afternoon, and night. At each age, a 20 min segment of video from each time of day was analyzed. Every minute was annotated to identify the behavior that hens spent the majority of their time performing. Data were averaged to calculate the percentage of hens engaged in each behavior per cage. The total count of aggressive bouts was recorded across the 20 min period. Data were analyzed with a general linear model utilizing the variables time of day, density, age, and the full factorial of interactions. Intermediate stocking densities displayed the lowest percentage of crouching (p = 0.009) and aggressive acts per hen (p < 0.0001). Hens stocked at 1341.93 cm² walked the most (p < 0.0001). Hens were seen standing and preening (p < 0.0001) more in the morning, crouching and sham dust bathing (p < 0.0001) more in the afternoon, stretching less while feeding and drinking, and being more aggressive at night (p < 0.0001). Finally, as hens aged, they began to stand and crouch more (p < 0.0001) and preen (p = 0.013), walk (p < 0.0001), and demonstrate aggressive behaviors (p = 0.007) less. In conclusion, the majority of behaviors assessed were not influenced by stocking density. However, the different amounts of aggression between the treatments could indicate higher stress and frustration, which warrants more investigation. Full article