The aim of this study was to evaluate the effect of genotype (Isa Brown and New Hampshire) on egg quality in a floor rearing system. Fifteen eggs per group were collected at 32 weeks of age and analyzed for external and internal quality parameters (egg weight, shape index, albumen height, Haugh unit, yolk color, and shell breaking strength), as well as for chemical composition (dry matter, minerals, protein, and lipids). Eggs from Isa Brown hens exhibited greater egg weight, higher shape index, and superior shell breaking strength, whereas New Hampshire eggs had more intensely pigmented yolks. No significant differences were observed in albumen height or Haugh units between the genotypes. Regarding chemical composition, significant differences were found only in lipid content, which was higher in New Hampshire eggs. No significant differences were detected in dry matter, mineral, or protein content.

Local chicken breeds are increasingly being reconsidered as a means to produce distinctive meat in non-conventional systems while also supporting the conservation of endangered genetic resources. This study compared Banat Naked Neck (BNN) and Svrljig hen (SH), two Serbian indigenous breeds, reared under identical pasture-based conditions and slaughtered at 12 or 14 weeks. Carcass traits, including linear measurements and carcass composition, were evaluated in 40 males (10 per breed per age), while breast and thigh-with-drumstick meat quality (proximate composition and fatty acid profile) was analysed in 80 samples (10 per tissue per group). Data were analysed using two-way ANOVA, and multivariate patterns were explored using PCA and residual Spearman correlation analysis. BNN and SH showed similar slaughter weights, whereas slaughter at 14 weeks increased carcass conformation measures and conformation indices (p < 0.05). Breed differences were most evident in carcass part distribution and tissue partitioning within cuts: BNN had a higher breast proportion and breast meat yield, whereas SH meat was leaner and thigh with drumstick meat showed higher Σn − 3 and a more favourable Σn − 6/Σn − 3 ratio. PCA indicated clearer breed separation in thigh meat than in breast meat, consistent with the univariate lipid results, and residual correlations highlighted expected allocation trade-offs among carcass and cut components. Overall, slaughter at 14 weeks improved carcass value, and both breeds offer complementary traits for market-oriented conservation through use.

The aim of the research was to determine the quality characteristics of eggs in retail stores on the Belgrade market during two summer seasons characterized by high temperatures. The research was conducted over two consecutive years (2024 and 2025) and included all grade M eggs available in retail chains (10) on the market. External and internal egg quality traits were analyzed, including egg weight, yolk color, Haugh units, shell thickness, and shell cleanliness, and evaluated by year and within two egg age categories (1–7 and 8–15 days). The average temperature during the experimental period was 27.6°C in 2024 and 25.4°C in 2025. Based on the results of the study, Haugh unit values ranged from 60.1 in 2024 to 68.4 in 2025. Compared to the other analyzed quality characteristics, Haugh units units exhibited the greatest sensitivity to high temperatures during summer months, while the effects of year, egg age, and their interaction were statistically significant. The obtained results indicate potential critical points in the ‘farm-to-consumer’ supply chain, highlighting the need for systematic monitoring of egg quality in retail stores, particularly during the summer months, in order to maintain it. The findings also underscore the importance of educating all stakeholders in the food supply chain, including consumers, to maintain egg safety and nutritional value under more frequent climate extremes.

To enhance the safety and efficiency of broiler nutrition, this study investigated the effects of a synbiotic product containing both probiotic and prebiotic components, administered through drinking water. The experiment was conducted on 600 Cobb 500 broilers divided into control and treatment groups. Over a 42-day fattening period, key production parameters - including feed intake (FI), average daily gain (ADG), feed conversion ratio (FCR), and the European Production Efficiency Factor (EPEF) - as well as slaughter traits were monitored. Synbiotic supplementation significantly improved growth performance, feed efficiency, and overall production outcomes. A higher carcass yield and a trend toward an increased proportion of breast muscle were also observed in the treated group. The findings suggest that synbiotics can be a valuable functional additive in broiler production, contributing to improved growth and carcass quality without adverse effects on animal health.

The aim of this study was to determine the quality of eggs available in Belgrade supermarkets during different seasons (winter, spring, summer), for various housing systems (cage, floor, and free-range), and to assess the representation of eggs from cage and non-cage systems in the year when Serbian egg producers have been granted an extended transitional period to comply with animal welfare legislation banning conventional cage systems. The research covered nine Belgrade supermarkets. All egg producers representing the three housing systems were recorded, and eggs up to 15 days old were tested for external and internal quality traits. The results show that cage-system producers remain dominant on the market, with a share ranging from 45.5% in winter to 50% in spring and summer. The share of floor (non-cage) eggs was 36.6% in winter and 30% in spring and summer, while free-range eggs had the lowest representation during all three seasons (around 20%). The findings indicate variability in egg quality traits influenced by both season and housing system as the second studied factor. Haugh Unit (HU) values, which represent an aggregate indicator of egg quality, were highest in winter, averaging 76.29 for the cage system, 76.31 for the floor system, and 77.28 for the free-range system. In spring and summer, lower HU values were recorded for all three systems, with a more pronounced decline in the non-cage systems. It can be concluded that there is a growing trend in the supply of eggs from non-cage systems in Belgrade supermarkets, which is more favorable in terms of animal welfare. The development of these systems could be further supported through education of producers and consumers, as well as through research and producer incentives. Although the study focuses on egg quality at the market level, and thus reflects the quality of the product reaching consumers, it also indicates potential weaknesses in the "from producer to consumer" chain. Therefore, it can be a starting point for future research on the entire system of egg production and distribution.

Indigenous and local chicken breeds can be used as slow-growing genotypes in non-conventional production systems, thereby ensuring consumer preferences for meat from these systems while conserving endangered animal genetic resources. This study aimed to examine and compare the potential of indigenous Banat Naked Neck (BNN) and Svrljig hen (SH) chickens in meat production under defined rearing conditions and con-tribute to the economic interest in the survival of these breeds. The growth of BNN and SH chickens up to the age of 12 and 14 weeks was analysed for a total of 240 individuals. Carcass yield and quality were analysed on a sample of 10 male chickens of each breed and slaughter age, a total of 40 chickens, based on measures of carcass conformation, processed carcass yield, proportion of main and edible carcass parts, and meat yield in main carcass parts. The quality of breast meat and leg meat is determined by analysing the basic chemical composition, fatty acid content and certain physical properties (cook-ing loss and tenderness). Breeds BNN and SH have a similar line of growth and final body weight at the ages of 12 and 14 weeks. The advantages of the BNN breed are in the higher yield of processed carcass, a higher proportion of breast and breast meat compared to the SH breed. On the other hand, SH chicken meat has a lower fat content, a higher n-3 fatty acid content and a more desirable n-6/n-3 ratio. Slaughter at an older age is justified in better carcass conformation and higher yields of carcass, breast and leg meat. Keywords: meat quality, indigenous breed, Banat Naked Neck, Svrljig hen, slaughter age.

This study aimed to explore how hybrid varieties impact broiler chickens’ production and slaughter performance. We applied standard rearing techniques over a 42-day period. The trial involved a total of 420 broiler chickens of the following hybrids: Cobb 500 and Ross 308. Weekly performance tests were conducted, assessing average daily gain, feed consumption, feed conversion rate, mortality, and European Poultry Efficiency Factor. After controlling for final body weights on the 42nd day, a random sample of 12 broilers per genotype, with an equal gender distribution, was selected for slaughter parameter analysis. Following slaughter traits were determined: pre-slaughter weight of chickens, slaughter yield, share of abdominal fat, chicken thigh circumference, and chest angle. The results revealed no significant difference in food consumption between the examined hybrids. Chickens of the Cobb 500 genotype exhibited significantly higher (p<0.01) gain and a more favorable feed conversion rate. Due to its better vitality, feed conversion rate, and gain, Cobb 500 chickens demonstrated significantly higher (p<0.01) European Poultry Efficiency Factor values. In contrast, Ross 308 chickens displayed statistically significantly lower (p<0.05) slaughter yield and chest angle values. At the same time, the proportion of abdominal fat and chicken thigh circumference showed no significant difference between the tested hybrids.

In order to preserve indigenous and locally adapted breeds through development programs for sustainable egg and meat production, it is necessary to have more data on the potential of these breeds in different production conditions. Accordingly, the objective of the study was to determine and compare the reproductive potential, production performance and egg quality of two indigenous poultry breeds: the Banat Naked Neck (BNN) and the Svrljig Hen (SH), in improved growing conditions (nutrition, photoperiod and housing) in relation to the traditional rearing of these breeds. Four flocks for each breed were housed in floor pens in a closed facility during the winter months, and then in the vegetation season (April-September) they were kept in mobile cages in the pasture. The duration of the photoperiod in the facility was 15 hours, and in the pasture, they were exposed to the natural duration of daylight. The layers were fed ad libitum with balanced complete mixtures for layer-line hybrids and during the vegetation season supplemented with food found in the pasture around the mobile cage. The reproductive potential of BNN and SH hens was determined on the basis of the age of the hens at the beginning of laying, the age at the peak of laying and the number of eggs per housed hen. The egg hatching properties were examined based on the percentage of chicks hatching in relation to the number of laid and fertilized eggs. Data on the quality of table eggs were obtained by testing over eight-week periods during the entire laying period. Under the applied rearing, nutrition and photoperiod conditions, BNN hens achieved production in accordance with their genetic potential defined by the breed standard, while SH layers with 126.43 eggs/housed hen achieved production higher than the breed standard. The egg production of these two breeds of hens differed in the intensity and persistence of laying, which, in addition to a higher peak of laying, resulted in a higher production of egg/housed hen BNN (146.71) compared to SH. On the other hand, parameters of table egg quality, i.e., shell quality and egg albumen/yolk ratio, were significantly better in SH. Also, SH had a higher reproductive potential compared to BNN hens based on the percentage of fertilized and hatched eggs.

The aim of the study was to evaluate the effect of three protein levels (with or without protease enzymes) on the weight and percentage yield of each meat class in two genotypes of broiler chickens (fast-growing hybrid Cobb 500 and medium-growing hybrid Master Gris). Each genotype was divided into a control group (C group) fed with a commercial feed mixture and an experimental group fed with a low protein diet of 4% (E-I group) or 6% (E-II group) in relation to the control group, with the addition of 200 mg/kg Ronozyme ProAct (E-I group) or 300mg/kg Ronozyme ProAct (E-II group). Weight and percentage yield of the meat classes were influenced by the genotype. The fast-growing hybrid Cobb 500 had higher masses of all meat classes and a higher percentage of class I meat, while the percentage of class II and III meat was lower than in the medium-growing hybrid Master Gris (P<0.05). Feeding had no effect on the weight and percentage yield of the individual meat classes in either hybrid (P>0.05).

Functional foods are foods that offer health benefits over and above their nutritional value. As eggs are a food of global importance, many authors believe that they are an ideal candidate for functional foods of the future, as it is possible to influence their chemical composition through production technology. Vitamins are one of the most important groups of micronutrients essential for human health, and eggs are recognised as an important source of vitamins in the diet, especially fat-soluble vitamins. The egg yolk contains large amounts of vitamins A, D, E and K. Eating two eggs a day covers 10% to 30% of a person's vitamin requirements. This paper reviews the results of a large number of researchers on the influence of various aspects of production technology on the content of fat-soluble vitamins in eggs. Most attention has been paid to the influence of vitamin supplements in feed for laying hens, but also to the influence of the rearing system and the genotype as well as the interaction between the vitamins.

The objective of the study is to determine the share of eggs from non-cage production systems compared to eggs from cage systems, in the year when the extended transitional period expires (December 2023) for Serbian producers to comply with the welfare legislation, mandating the transition from the conventional cage breeding system to permitted systems (enriched cage system and non-cage systems (floor, aviary, free breeding - free ranges, organic production). Also, the objective of the study is to determine the structure of consumers within the group valueing the breeding system, which declares that it prefers free range eggs and organic eggs. The examination of the Belgrade market supply of eggs, including supermarkets (11), green markets (5) and specialized stores (5), and consumer attitudes was conducted through a survey (247 respondents in the Belgrade region). According to the results of the survey, it can be concluded that the supply of eggs from non-cage systems is minor, compared to eggs from the cage system, which have a share of 100%, it is 81.82% for eggs from the floor system, 54.54% for eggs from free range and 9.10% for organic eggs. The supply of organic eggs on the market is insufficient and mainly associated with specialized stores. For about 30% of consumers, the egg production system is very important, whereby the majority of consumers (53.45%) would prefer the eggs from free ranges, and among them the largest share are women (76.03%), consumers with higher education (67.10%), employed (78.38%), aged 36-55 and with higher monthly incomes. Based on the research results, it can be concluded that the process of harmonizing egg production with welfare regulations has an impact on the egg market, i.e. resulting in changes in the sense of greater share of eggs from non-cage systems compared to similar research in the earlier period. At the same time, although there is a growing awareness among consumers about the importance of the production/rearing system, it is still insufficient compared to certain European countries. The development of non-cage systems, as more favourable from the point of view of welfare and consumer expectations, should be given greater attention in the coming period, by acting through regulatory measures, education of producers and consumers, research and support in terms of incentives, subsidies and loans to producers who switch to alternative systems of raising laying hens.

Summary This study aimed to assess the effects of different dietary levels of the protease enzyme and sex on skin, bone and muscle yields and percentages of breast, drumsticks and thighs as the most valuable carcass parts of broilers. A total of 300 one-day-old, mixed-sex broiler chickens (Cobb 500) were randomly divided into 3 dietary treatments with different levels of protease supplementation (group C: a standard diet without Ronozyme ProAct; group E-I: a diet with 200 mg/kg Ronozyme ProAct and a 4% crude protein reduction compared to the standard diet; and group E-II: a diet with 300mg/kg Ronozyme ProAct and a 6% crude protein reduction compared to the standard diet). All diets were maize- and soybean meal-based. Feed and water were provided ad libitum throughout the 49-day feeding trial. The results obtained indicate that the dietary treatments had no significant effect on skin, bone and muscle yields and percentages of the drumsticks, thighs and breast (P > 0.05), except for the breast muscle weight in the female chickens (especially between the E-I and E-II groups), and the drumstick bone percentage in the males between the C and E-2 groups (P < 0.05). In all three groups, the male chickens exhibited higher weights of skin, muscle and bone in breast, drumsticks and thighs than the female chickens, and the differences were not significant only in the skin weight of drumsticks and thighs (P > 0.05). The females had a higher yield of muscle tissue in breast and drumsticks, a higher percentage of skin in drumsticks and thighs, and a lower percentage of bone in drumsticks and thighs than the males (P < 0.05). Major differences resulted from the effect of broiler sex, whereas the dietary treatments containing 3 levels of protease supplementation had a very small effect on the yields and percentages of skin, bone and muscle in breast, drumsticks and thighs.

The quality of table eggs obtained from Hy Line hybrid layers reared in battery system and native population of Naked-neck hens reared in extensive system, was studied. The external properties (egg mass, shape index, cleanliness and eggshell colour), internal properties (egg-white colour, haugh units, egg yolk colour, egg-white/yolk ratio), properties of egg and egg shell quality (mass, thickness, defomration and breaking force) were observed. Òhe trial was carried out on the Experimental farm of the Institute and it lasted 28 weeks, i.e. seven 4-week long study periods. The results show that Hybrid Hy Line in battery system had eggs of better quality. Its eggs had higher average mass, better egg-white quality and thicker and firmer eggshell. Naked-neck native hens reared in extnesive system with limited range gave eggs with lower shape index (more pointy eggs), significantly lighter colour of egg shell (2.25; 3.37) and significantly more intensive yolk colour (13.03; 11.52).

The objective of the present trial was to evaluate the effects of nettle leaves (Urtica dioica) supplementation, broiler gender and muscle portion on meat fatty acid and mineral profiles. Prior to the trial, a total of 600 one-day-old Cobb 500 broiler chickens of both genders, equally, were randomly divided into three groups: a basal diet (control group) and a basal diet supplemented in the last two weeks of fattening with fresh nettle leaves (30 g/kg diet) or with oven dry nettle leaves (5 g/kg diet). After reaching 42 days of age, twenty birds per diet group were randomly selected (four birds per box, both genders equally) and slaughtered, and breasts and drumsticks were collected for analysis. The dry nettle supplementation increased the MUFA and lowered the PUFA, n-6 and n-6/n-3 ratio, mainly in female broilers (p < 0.05). Drumsticks had higher MUFA and PUFA and lower SFA and n-6/n-3 ratio compared to breast meat (p < 0.05). The addition of nettle to broiler diet increased Fe, Zn and Se and decreased Ca levels, mainly in drumsticks (p < 0.05). Furthermore, drumstick meat had more elements with proven health benefits, such as Fe, Zn, Ca and Mn, than breast meat. This study suggests that feeding Cobb 500 broilers with the addition of nettle leaves can significantly change meat fatty acid and mineral composition, but this effect differed between gender and portion.

The aim of this research was to examine the influence of the year (production cycle) and laying age on the quality of eggs for consumption. Examination of certain properties of egg and shell quality was carried out over a period of three years continuously and in four evenly spaced time intervals (24, 35, 46, and 57 weeks of age). Determining the external quality of eggs included determining the weight and shape index. Examination of the internal quality of eggs included the determination of albumen height and Haugh units. At the same time, the quality of the eggshell involved the determination of the following properties: (weight, thickness, deformation, breaking force, and color of the shell). The obtained results showed that during three production cycles, the genetic progress of this hybrid was confirmed, which is primarily reflected in a statistically significantly higher (p<0.05) value of egg weight, egg white height, and Haugh's units in the third year compared to the first year examinations. Also, under the influence of this factor, statistically significantly higher values of weight and shell thickness and a darker shell color were determined in the third compared to the first year of research. No statistically significant differences were found for other examined parameters under the influence of this factor. In the presence of statistically significant influence (p<0.05), various laying ages were systematically examined for internal and external egg quality attributes alongside shell quality properties, excluding shell deformation. Egg weight increased significantly with increasing laying age, while shape index values, contrary to egg weight, decreased. The parameters of internal egg quality were worse with increasing laying age. Regarding the shell quality properties, it was found that the shell weight and thickness, similar to the egg weight, increased with the age of the layers, while the breaking force was found to be the lowest in the oldest layers. The interaction of both tested factors did not cause a statistically significant effect on tested egg quality traits.

The effects of feeding low dietary crude protein with supplemental protease and sex on the weight and percent yields of individual meat classes in broiler chickens of hybrid Cobb 500 were investigated. A total of 300 day-old broiler chicks were fed with one of the following three experimental diets: control group (C), the experimental group I (E-I) contained 4% less crude protein than the control (C) and were supplemented with protease (Ronozyme Pro Act) at a concentration of 200mg/kg feed and the experimental group II (E-II) contained 6% less crude protein and were supplemented with protease (Ronozyme Pro Act) at a concentration of 300mg/kg feed. Supplementation of protease to diets had no significant effects on weights of individual meat classes (P>0.05), as well as the percentage of meat classes, and the only differences were manifested between E-I and E-II (P<0.05, female broilers from the E-I group were had a higher percentage of class I meat and a lower percentage of class III meat compared to females from the E-II group). The effect of sex was manifested in the weights of all meat classes and the percentage of class I meat and class III meat (P<0.05).

The first few weeks after broilers hatch are the period of most intense bone growth and development, and the time when they are most susceptible to the influence of various external and internal factors. Research in the recent decades has focused on the involvement of melatonin in bone development during early life in chickens. Melatonin release from the pineal gland has a circadian rhythm, with the highest levels circulating during the night and decreasing during the light phase of the day. Various types of lighting are used in intensive broiler production. In this study, the effects of melatonin on the tibial structure and growth of broilers were investigated. During the first two weeks of life, two groups of chickens were kept under continuous light and fed the same diet, with the experimental group receiving melatonin in the amount of 0.03 g/kg of feed. The results obtained showed that the addition of melatonin in the diet had positive effects on the development and growth of the tibia, which was expressed in a significantly greater thickness of the diaphysis and cortical bone of the diaphysis, higher breaking force and higher values of alkaline phosphatase activity. The cortical bone mineral density of the tibia did not differ significantly between the groups of chicken.

This paper aimed to determine the effect of the rearing system and genotype of laying hens on the fatty acid composition of eggs. Seven times during the one-year production cycle, 15 eggs from all four experimental groups were taken, and fatty acid composition was determined on pooled samples. Based on the obtained results, it can be concluded that the highest content of SFA had organic New Hampshire eggs, MUFA organic Isa Brown eggs and PUFA floorproduced eggs. Regarding the ratio of n-6:n-3 PUFA, it can be noted that the organic eggs had a lower ratio compared to the floor eggs, as well as the New Hampshire breed compared to the Isa Brown hybrid.

The egg production sector is in a transitional period with regard to the permitted housing systems, i.e. rearing in conventional cages under certain conditions to the complete ban of any form of cage system. The changes were caused by concern for the layer wellfare but with the expected effects on productivity as well. The aim of the research was to determine the effects of the floor space allowance in cage and non-cage housing systems on the feather score and egg production of laying hens of three ages, from the aspect of the regulated minimum and optimal space in the cage system (C) and the space provided in the extensive rearing system with hens in smaller groups in the facility (extensive indoor -EI). In order to determine the feather score, the body weight of the laying hens and the weight of the eggs, three groups of laying hens were formed: C4 (564 cm2 per hen, cage system), C3 (751 cm2 per hen, cage system) and EI ( 3000 cm2 per hen, extensive indoor). The feather score and body weight of laying hens were determined in three ages of hens (30, 40, 50 weeks), by individual assessment and measurement of all hens in the experiment. The hen-day egg production and egg weight were determined in the same weeks of laying age. In addition to the expected decrease in feather score with the age of hens, results indicated a significant interaction between age and space allowance per hen. Observed by individual body parts, as well as based on the overall feather score, the space allowance per hen exhibited a full, cumulative effect at 50 weeks of age. Based on the space allowance, it was possible to rank the overall feather score, with the laying hens with the most space having the best feather score. The effect of the space allowance on the body weight of the laying hens was manifested through the space available on the feeder, which resulted in the lowest (p<0.01) body weight values recorded in laying hens of the C4 group. Egg production was not significantly influenced by the space allowance per hen (p=0.069), but a connection between egg production and the housing system can be concluded. The average egg weight, in addition to the known effect of layer age, was the lowest (p<0.01) in the group with the least space allowance per hen.