The antioxidative influence of dietary creatine monohydrate and L-carnitine on laying performance, egg quality, ileal microbiota, blood biochemistry, and redox status of stressed laying quails.

The experiment was implemented to assess the influence of dietary supplementation of laying quails with creatine monohydrate (CrM), L-carnitine (CAR) and their mixture (CrMCAR) as antioxidants against oxidative stress (OS) induced by 2.5 ppm lead acetate (LA) in drinking water on productive, physiological and microbial aspects. In total, 400 laying quail females at 10 wk of age were divided into a randomized design with 5 groups and 4 replicates of 20 birds each. Birds were fed ad libitum with a balanced diet for 8 wk. The control group was kept under no-stress conditions and was given fresh water without any additives (G1). While birds in other groups were exposed to OS induced experimentally by 2.5 ppm LA in drinking water with no feed additive (G2) or supplemented with 500 mg/kg CrM (G3) or 500 mg/kg CAR (G4) or combination of 250 mg/kg each of CrM and CAR (CrMCAR, G5) to feed mixture. Compared to G2, G5 demonstrated the reduction (P ≤ 0.05) of feed conversion ratio, feed intake, mortality and ileal total coliform, as well as serum and egg malondialdehyde and serum lipid hydroperoxide, uric acid, glucose, cholesterol, enzymatic activities (alanine aminotransferase, aspartate transaminase, alkaline phosphatase, creatine phosphokinase, γ-glutamyl transferase), and heterophils/lymphocytes ratio. In the meanwhile, there was an increase (P ≤ 0.05) in egg production, egg mass, and weight with the improvement of egg quality, serum sex hormones level and ileal lactic acid bacteria for G5 followed by G4 and G3. Moreover, G5 enhanced (P ≤ 0.05), the total antioxidant capacity of egg and serum glutathione, superoxide dismutase, catalase, glutathione peroxidase, protein and calcium levels. Therefore, dietary CrMCAR, CAR and CrM have analogous influence to control by improving the antioxidant and physiological parameters which resulted in better productive performance and egg characteristics of stressed quails. These antioxidants, especially in their equal combination, are beneficial to alleviate oxidative stress incidence and can be recommended for poultry feeding under various aspects of environmental stresses.

The Impact of a Phytobiotic Mixture on Broiler Chicken Health and Meat Safety.

The purpose of the study was to assess the effects of different doses of a phytobiotic mixture on selected production parameters and meat quality and to assess the residue of the preparation in tissues and the possible toxic effects in broiler chickens. Broiler chicks aged 160 days, divided into four equal groups, were supplemented with the phytobiotic mixture at different doses, D1-0.5 mL/L, D2-1 mL/L, and D3-2 mL/L, four times during a 42-day trial. There were no statistically significant differences in weight gain per week of life and mortality in the birds. The study also demonstrated that the use of the mixture of phytobiotics had no significant effect on colour, pH, WHC, and natural leakage. However, a beneficial effect of the additive was found in the group treated with a dose of 1 mL/L, where less thermal leakage from the meat was demonstrated. Furthermore, significant differences in the change in thigh muscle tenderness were also observed. In the histopathological analysis of the liver no significant differences were observed. In addition, no residues of the mixture or its metabolites were found in the tissues analysed. In conclusion, the proposed scheme of administration of the phytobiotic additive, regardless of the dose, does not cause pathological changes in organs and does not carry the risk of residues of the product in tissues intended for human consumption.

The eggshell defect as a factor affecting the egg quality after storage.

The aim of the study was to assess the influence of shell defects on the quality of eggs after storage. The study material consisted of 1,800 brown-shelled eggs from cage rearing system which were candled on the day of laying to determine the shell quality. Eggs with the 6 most common shell defects (external crack, severe stripe marks, points, wrinkled, pimples, sandy) and eggs without defects (control group) were then stored for 35 days at 14°C and 70% humidity. The weight loss of eggs was monitored every 7 days, and the quality characteristics of whole eggs (weight, specific gravity, shape), shell (defects, strength, color, weight, thickness, density), albumen (weight, height, pH) and yolk (weight, color, pH) of 30 eggs from each group were analysed at the beginning (0 days) and after 28 and 35 days of storage. The changes resulting from water loss (air cell depth, weight loss, shell permeability) were also evaluated. The study showed that all investigated shell defects significantly influenced the characteristics of the whole egg during the storage, modifying traits such as specific gravity, water loss, shell permeability, albumen height and pH, as well as proportion, index and pH of the yolk. Furthermore, an interaction between time and the shell defects presence was found.

The sex impact on the technological and chemical characteristics of meat derived from the Polish native chicken breed.

The aim of the study was to evaluate the birds' sex as well as the caponisation influence on the technological traits of obtained meat, fatty acids profile as well as main chemical compounds distribution. In this study, 40 hens, roosters and green-legged partridge capons each were used (4 replications each). At 24 weeks of age, 2 birds from each replication subgroup were selected and slaughtered. During dissection analysis, pectoral and femoral muscles were sampled. Acidity, colour, tenderness, water holding capacity, drip and cooking loss were determined in the obtained material. The fatty acid profile of the meat was also determined, as well as the distribution of components in the pressed meat samples using FTIR spectroscopy. Statistically significant differences in the colour lightness index (L*) of the breast muscles were recorded, with cockerel meat being the darkest and capon meat the lightest. The greatest natural water loss was recorded in the hens' pectoral muscle; cooking loss was also the greatest in these samples. Roosters showed significantly the lowest content of monounsaturated fatty acids, at the same time the highest proportion of the n3 fatty acids group was found in capons. Irrespective of muscle, meat from roosters showed the highest susceptibility to oxidation (PI index). The variation in the chemical composition of the meat was confirmed by FTIR mapping.

The Quality of Eggs Derived from Japanese Quail Fed with the Fermented and Non-Fermented Rapeseed Meal.

The most popular protein source in poultry feed mixtures is soybean. However, cheaper and more available alternative protein sources are being sought, and feed manufacturers more and more often turn their attention to the post-extraction meals of local oil plants, e.g., rapeseed. Therefore, the effect of fermented and non-fermented post-extraction rapeseed meal used as a feed additive for Japanese quails was investigated on the eggs' quality. The study was performed on 280 females of Japanese quails fed with a mixture without rapeseed meal, with non-fermented post-extraction rapeseed meal (5%, 10% and 15%) and with fermented one (5%, 10% and 15%). During the experiment, eggs were collected from each group four times (every 4 weeks) and evaluated for their quality characteristics. The addition of 10% fermented rapeseed meal had the most beneficial effect on such eggs quality traits as egg weight, specific gravity, yolk index and color and albumen pH. However, in the majority of examined parameters, no significant differences were found between birds fed with soybean meal and those fed with fermented and non-fermented rapeseed meal (morphological elements proportions, yolk weight, albumen height and Haugh's units, eggshell quality). This supports the thesis that the use of rapeseed meals instead of soybean meals may allow obtaining the proper quality of animal raw materials at a lower cost and with the use of local feed resources.

The use of selected herbal preparations for the disinfection of Japanese quail hatching eggs.

The aim of study was to evaluate microbial and hatchability traits as well as chicks quality after hatching eggs disinfection with aqueous solutions of ginger (GR), garlic (GC), oregano (O), and cinnamon (C) extracts. The experiment was divided into 2 stages, at preliminary in vitro stage antimicrobial susceptibility of plant extracts (PEs) was tested against reference strains from the American Type Culture Collection. O and GC extracts had the best antimicrobial properties (P < 0.05). Then in in vivo stage 2,400 Japanese quails hatching eggs were divided into 6 groups, 400 eggs each. Eggs from first group were not disinfected (NC, negative control), eggs from second group were disinfected by formalin fumigation (C, positive control), in other groups 5% aqueous solutions of plant extracts of GR, GC, O, C were applied by spraying respectively. After standard incubation fertility, hatchability and periodical embryonic mortality were calculated as well as the body weight and livability of chickens during 14 d of rearing. Egg disinfection by aqueous solution of PEs led to maintain the hatchability, chick weight at hatch and post hatch body weight and early mortality of birds. Exclusion of any fungal isolates on eggshell surface was induced by GC followed by O and C groups (P < 0.05). In case of the bacteria colonies reduction only GR extract was effective. Chosen plant extracts may be treated as safe and alternative substances to traditional disinfectants of hatching eggs.

Environmental Enrichment as Part of the Improvement of the Welfare of Japanese Quails.

The aim of this study was to evaluate the indicators of the behavioural and physiological welfare of Japanese quails (Coturnix japonica) as possible responses to the enrichment of the birds' habitat. The study sample consisted of 280 Japanese quails (224 ♀ and 56 ♂, respectively). Birds of 5 weeks of age were randomly divided into seven equally sized groups and then divided into replication subgroups (four per group, 10 birds in each replication). Birds were maintained in 0.5 m2 cages with unrestricted access to water and food. The experimental factor was the presence or absence of enrichment of the birds' cages: the nest box, scratcher, plastic corrugated pipe (tunnel), limestone cubes, sandbathing box and feeder box with a drilled cover. Quails were subjected to behavioural tests (tonic immobility and open field tests) and, after 6 weeks, blood samples were taken from them to determine their biochemical indices as well as their cortisol and corticosterone levels. An additional element was the assessment of fertility indices. The presence of enrichment was shown to reduce behavioural disturbances in Japanese quails. This study also found that the colour and shape of an object were very important regarding the birds' interest in it. Additionally, individuals kept in enriched cages, who were allowed to exhibit their natural behavioural patterns, had lower stress levels.

The Use of the Dynamics of Changes in Table Eggs during Storage to Predict the Age of Eggs Based on Selected Quality Traits.

The aim of the study was to determine daily changes in some egg quality parameters, indirectly reflecting egg freshness, and to assess the possibility of predicting time from laying using mathematical methods. The study material consisted of 365 table eggs of medium (M, ≥53 g and <63 g) and large (L, ≥63 g and <73 g) weight classes (commercial stock, cage system, brown-shelled eggs) collected on the same day. Eggs were numbered individually and placed on transport trays and stored (14 °C, 70% RH). Every day, for 35 days, egg quality characteristics were analyzed (10 eggs per group). The change of traits in time was analyzed on the basis of linear and polynomial regression equations, depending on the trait. Based on model fitting, eight traits were selected as those most affected by storage time: egg weight and specific weight, Haugh units, albumen weight, air cell depth, yolk index, albumen and yolk pH. These traits, excluding those related to the weight, were then used in a multiple linear regression model to predict egg age. All regression models presented in this study were characterized by high predictive efficiency, which was confirmed by comparison of the observed and estimated values.

The Impact of Package Type and Temperature on the Changes in Quality and Fatty Acids Profile of Table Eggs during Their Storage.

The aim of the study was to evaluate the possibility of reducing changes in the quality of consumer hen eggs by storing them in various package type and under various temperature conditions (room and refrigeration). The material consisted of 960 chicken eggs packed in cardboard or plastic boxes, 10 pcs in each. Half of the packages were stored at room temperature (21 °C), the rest in the refrigerator (5 °C). The eggs were stored for 28 days qualitatively evaluated at 14-day intervals. The characteristics of whole egg (weight, specific weight, proportion of morphological elements, air cell depth) as well as of shell (weight, color, crushing strength, thickness, density, water conductivity), albumen (height, Haugh units, weight, pH) and yolk (weight, color, pH) were analyzed. The fatty acids profile of yolks was also evaluated as a freshness indicator. Packaging types available on the market, apart from its marketing and eggs protection function, can also influence the quality and stability of the product during storage. The use of plastic boxes can help to maintain higher eggs quality during the storage period, even after a significant extension of the storage time. Eggs stored in plastic boxes at room temperature had very similar results to those stored under refrigeration using conventional cardboard boxes. This effect is probably related to the lower permeability of plastic boxes in comparison to cardboard ones, but detailed research work in this direction is necessary to verify this relation.

The Antioxidative Impact of Dietary Vinegar and Rocket Salad on the Productivity, Serum Oxidation System, and Duodenal Histology of Chickens.

The purpose of the study was to investigate the ameliorative effect of dietary rocket salad and apple cider vinegar on the oxidative stress (OS) status of broilers. Specifically, 720 Ross 308 chicks were divided into six groups: negative and positive controls (NC and PC with and without additives, Vi1 and V12 experimental groups fed with diets mixed with 5 and 10 mL of vinegar/kg, and Ro1 and Ro2 groups fed with diets mixed with 2 and 3 g of rocket salad/kg, respectively). The experimental groups Vi1 and Vi2 were fed with feed mixture moisturized with 5 and 10 mL of vinegar/kg, and Ro1 and Ro2 were fed with 2 and 3 g of rocket salad/kg, respectively. The birds' productivity, oxidative serum parameters, and morphometric indices of the gastrointestinal tract were registered at 6 weeks of rearing. The vinegar or rocket salad additive had powerful potentials to significantly suppress (p ≤ 0.05) OS through improving the birds' survivability, body weight gain, feed conversion ratio, and carcass yield. The highest villus height and villus height/crypt depth ratio of the duodenum were achieved by Vi2, Ro1-2, and NC (p ≤ 0.05). The villus surface area and muscular layer thickness were smallest in the PC, while they did not differ significantly in other groups (p > 0.05). Similar relationships were found in serum superoxide dismutase, glutathione peroxidase, hydroperoxide, and malondialdehyde; however, higher doses of both additives were more effective. It seems that liquid vinegar and rocket salad could have beneficial influences on the antioxidant status of birds.

Growth performance and meat quality of meat-type guinea fowl fed different commercial diets.

The aim of study was to assess the growth performance, meat quality, and fatty acid composition of meat-type guinea fowl fed balanced commercial diets under two different feeding programs, similar to those for slaughter turkeys and broiler chickens, respectively. A total of 80 4-week-old meat-type guinea fowl divided into two groups (four replicates per group; 10 birds in each replicate) were raised for 14 weeks. One group received commercially available diets in a three-phased program (TM group), whereas the other group was fed commercial diets in a two-phased program (CM group). Growth-performance-related traits were recorded. At the end of rearing (14 weeks of age), eight birds from each group were slaughtered. Carcass yield and technological traits of meat (pH, color, water-holding capacity, natural and thermal loss, tenderness, fatty acid profile) were analyzed. Groups did not differ in terms of body weight as well as carcass yield and characteristics. There was no difference in meat quality and the fatty acid profile of breast and thigh meat of guinea fowl from TM and CM groups. The findings of this study suggest that both commercial diets (for broiler chickens and turkeys) can be used in meat-type guinea fowl rearing. Due to the lower price of diets fed to the CM group and the lack of significant variation in meat quality traits, its use seems to be more justified from an economic point of view.

Pedigree Analysis of Warmblood Horses Participating in Competitions for Young Horses.

The aim of the study was to characterize the population structure and assess the genetic diversity of warmblood horses used in the show jumping discipline. Pedigree data of 1,048 horses participating in the Polish Championships for Young Horses were analyzed. The pedigree of these animals included 12 863 individuals. The study consisted in analysis of the pedigree structure of the horses and characterization of the homozygosity and genetic diversity in the population. It was found that pedigree completeness and depth were sufficient for reliable assessment of the genetic diversity in the analyzed population. Although the average inbreeding coefficient exhibited at an acceptable level (approx. 1.01%), the increasing percentage of inbred animals seems disturbing. The results have shown that modern sport horses are derived from a small number of high-quality sires whose offspring were intensively used for breeding-bottleneck effect. In consequence, a greater part of the genetic variation reduction was observed in the non-founder generations. Given the changes in the studied population, the level of inbreeding in modern sport horses should be monitored, and pedigree data should be effectively used in selection for mating.

The Variability of Quality Traits of Table Eggs and Eggshell Mineral Composition Depending on Hens' Breed and Eggshell Color.

The aim of the study was to evaluate the relationship between the eggshell color parameters and its mineral composition as well as the internal quality of eggs derived from various breeds of hens, varied by eggshell color: seledine from Araucana, brown from Marans, and white from Leghorn. The sample consisted of 180 eggs (60/group) The eggshell color was measured using CIE L*a*b* system. The quality evaluation included traits of whole egg (weight, specific gravity, proportions of elements, shape index), yolk (weight, color, index, pH), albumen (weight, height, pH), and shell (color, strength, weight, thickness, density). The mineral composition of eggshells was analyzed. The eggs origin affected the quality characteristics of particular egg elements (p < 0.001). However, the impact of analyzed colors on the egg quality traits varied, and in the case of whole egg and albumen traits the most favorable was the white color (p ≤ 0.05), while in the case of the strength of shell or its thickness it was the dark brown color (p ≤ 0.05). The eggshell color influenced variations in its mineral composition (p < 0.001) except potassium and sodium content, while the proportion of particular mineral elements in shell was correlated with the L*a*b* color space coordinates (p ≤ 0.05).

The Influence of Sex on the Slaughter Parameters and Selected Blood Indices of Greenleg Partridge, Polish Native Breed of Hens.

The aim of the study was to assess the influence of sex, including caponization, on selected physiological and productive traits of Greenleg partridge (GP) birds. The study material consisted of 120 GP chicks (40 females and 80 males), divided into 3 equal groups (4 replication in each) and kept in litter system and fed ad libitum. A total of 40 cocks have been surgically castrated. The body weight (BW) of birds were measured biweekly. At the age of 24 weeks 8 birds/group were slaughtered, their carcasses were subjected to simplified dissection. Blood samples were collected and among others biochemical profile of serum was established. The lowest BW, regardless of age, had hens. From 18th week capons had the highest BW and finally it was similar to cocks. Cocks demonstrated, significantly, the highest carcass yield, however, the biggest proportion of breast muscles were stated in capons carcasses. The effect of sex is very clear in case of abdominal fat pad. The highest proportion of it was found in females but the lack of sex hormones in capons also contributed to a higher fat accumulation. The serum profile showed that the sexual maturity of hens increased lipids content (cholesterol, trigliceroles) caused by laying production.

Citric acid as a factor limiting changes in the quality of table eggs during their storage.

The aim of the experiment was to evaluate the potential use of citric acid as a modifier of quality changes in table eggs during their storage. About 780 table hen eggs were collected on the same day. They were numbered individually and placed on trays 30 pcs on each. Control group (CA0) consisted of eggs unmodified with any additional substances. In experimental groups CA10 and CA15, eggshells were sprayed with the aqueous solution of citric acid (10 and 15% concentration, respectively). At the start of the experiment, only quality traits of eggs from the control group were analyzed. The remaining eggs were stored at 14°C and 70% RH (typical storage conditions). Their quality was evaluated after 7, 14, 21, and 28 d. The depth of the air cell, egg weight and specific gravity, traits of shell (permeability, strength, weight, thickness, density), and egg content (pH of yolk and albumen, Haugh units, yolk weight and color) were evaluated each time. The use of citric acid decreased the severity of qualitative changes. Citric acid-treated eggs demonstrated smaller weight loss, shallower air cell, higher structural albumen, less-intensive water diffusion from albumen to yolk indicating the improved resistance of the vitelline membrane. Owing to the fact that citric acid is accepted and recognized as a safe food preservative is a relatively cheap and available substance, it seems that it can be used to inhibit quality changes in table eggs during their storage.

Fatty acids profile, cholesterol level and quality of table eggs from hens fed with the addition of linseed and soybean oil.

The study objective was to assess the impact of soybean (SO) and linseed oil (LO) added to feed mixture for laying hens upon the quality characteristics of table eggs, their fatty acid (FA) profile and cholesterol level. The material consisted of eggs from hens fed with a mixture without oil and with the addition of LO or SO in a dose of 2.5%. Eggs were subjected to quality assessment. FA profile and cholesterol content in yolks were determined. The results indicate no negative changes in eggs' quality caused by supplementation. An increase was observed in the n3 FA content in egg yolk in experimental groups, as well as all PUFA (polyunsaturated fatty acids) proportions. No negative impact of these oils on the level of cholesterol was noted. As a consequence, the analysed feed additives can be safely applied as an appropriate material in poultry nutrition to enrich eggs with PUFA.

Use of reactive oxygen species (ozone, hydrogen peroxide) for disinfection of hatching eggs.

The sample consisted of 480 hatching eggs of Japanese quails and was divided into 4 groups. Before the transfer to the incubator, the first group was not disinfected (negative control). In the second group, eggs were disinfected by means of formaldehyde fumigation (positive control). In the third and fourth group, reactive oxygen forms were used for disinfection- perhydrol (H2O2) and ozone (O3), respectively. Eggs were incubated under standard conditions. On the 14th D, eggs were candled, and proportions of fertilized eggs and died embryos were calculated. In addition, samples were collected for microbiological examination. After 17.5 D, the results of the whole hatching were evaluated. Chicks were reared for 14 D. Their survivability and body weight gain were recorded. Disinfection by means of reactive oxygen forms did not prove to be more effective in reducing the number of bacterial colonies on the shell. Reduced hatching and significantly increased mortality in the O3 group may indicate the negative impact of this gas on developing embryos. The results of hatching from eggs disinfected with H2O2 did not differ from those obtained in control groups. The biggest chicks were obtained from O3 disinfected eggs. However, during rearing, their growth did not match the one observed for birds in the remaining groups. Chicks hatched from eggs disinfected with H2O2 were characterized by the largest survivability. Disinfection with reactive oxygen forms did not significantly improve the hygiene of hatching eggs, hatching performance, and quality of hatched chicks. Hydrogen peroxide, whose application offered satisfactory hatching results, may be the recommended disinfectant. On the other hand, O3 appears to be undesirable because of its negative impact on bird embryos.

The Impact of Eggshell Colour on the Quality of Table and Hatching Eggs Derived from Japanese Quail.

The aim of the study was to evaluate table and hatching eggs of Japanese quails (Coturnix coturnix japonica) depending on the eggshell colour. The research was carried out in two stages, in terms of table eggs' quality and their biological value as hatching eggs depending on the eggshell colour. In both stages, 300 Japanese quail eggs were used in each (600 in total) divided into two equal groups: with a brown-spotted shell, with a uniform shell in shades of blue. In the 1st stage, quality characteristics of the whole egg (weight, specific gravity, proportions of particular elements), yolk (weight, colour, index), albumen (weight, height) and shell (colour, strength, weight, thickness, density) were evaluated. In the 2nd stage, eggs were incubated under standard conditions and following biological characteristics were analyzed: eggs fertility, embryo mortality, hatchability of fertile and set eggs, body weight of hatchlings and their proportion in egg weight. The shell colour, "blue" or spotted, of Japanese quail eggs, does not appear to influence their quality if they are intended for consumption. However, the hatching results and body weight of obtained chicks of Japanese quail may be affected by the eggshell colour.

Time of sexual maturity and early egg quality of Japanese quails affected by in ovo injection of medicinal plants.

The aim of this study was to evaluate the time to sexual maturity and quality of initial eggs of Japanese quail affected by in ovo injection of plant extracts: ginger (GR), garlic (GC), oregano (O) and cinnamon (C). In total, 2400 eggs of Japanese quails were divided into six groups on the fifth day of incubation. Group I was the control group (NC), which was not injected. Other eggs were injected with 0.1 mL of liquid: group II - the positive control (PC) - with distilled water, group III with 1 % solution of GR, group IV with GC, group V with O and group VI with C. After hatching, the birds were reared in a cage system and fed with balanced mixtures, and 24 h lighting was used. The time at which birds reached sexual maturity was registered, while in the seventh week of rearing, 120 eggs were subject to quality evaluation. The traits of a whole egg (shape index as the ratio of egg width to egg length, weight, specific gravity), shell (strength, weight, thickness and density), albumen (weight, height), yolk (color, weight, index) were evaluated. At the earliest, on 36th day of life, eggs were laid by birds from the GC group, followed by C (37th day), O and NC (38th day), GR (39th day), and PC (41st day). During the first 2 weeks significantly more eggs were collected from the GC than from the other groups. The heaviest eggs derived from GC and GR groups, whereas the lightest came from the C group. Eggs from the GC group had the best shell strength and the greatest proportion of yolk. The use of medicinal herbs by injection in ovo may considerably modify both time of sexual maturity and quality of the initial eggs of Japanese quail.

Content of selected inorganic compounds in the eggs of hens kept in two different systems: organic and battery cage.

Recent years have seen increased interest in the influence of bioactive dietary components on human genes and gene expression. A good source of many bioactive substances is the chicken egg. The egg is considered to be an excellent food provided by nature. It is a good source of nutrients such as vitamins A, B2, B6, B12, D, E and K, as well as elements including phosphorus, selenium, iron, zinc, magnesium and calcium. The research material use in this study consisted of eggs from hens kept in two different systems: organic and battery cages. The content of calcium (Ca), magnesium (Mg) and zinc (Zn) was determined in the egg contents - in the yolk and white respectively. The content of elements was determined by atomic absorption spectrometry (AAS) using an AA280 FS spectrometer with the automatic dilution of standards and samples. The eggs from the organically raised hens had a higher calcium, magnesium and zinc content. The greater variation in the Ca, Mg and Zn content in the organic eggs is due to the more individualized feeding system. The rearing system of the hens significantly affects the concentration of elements in the egg. The results of this research indicate that eggs from organic farming systems have a richer chemical composition in terms of the content of nutrients such as calcium, magnesium and zinc compared with eggs obtained from caged hens. Therefore, consumers purchasing eggs should consider the system in which the hens were reared, as eggs can be a valuable source of these elements in the diet.