Zdenka Škrbić

• Institute for Animal Husbandry

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 c...

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 fee...

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 sys...

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 diff...

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 fr...

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...

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 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)...

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 e...

Key questions for a local broiler farm are: which broiler hybrid to rear and which industrial feed to use? To show how farmers can manage them, a combination of biological tests and feed characterizations of the most commonly used hybrids and broiler feeds in the local (Serbian) market was designed and performed. The hybrids Cobb 500 and Ross 308 w...

The aim of this study was to determine the effect of the rearing system (floor and organic) and the genotype of laying hens (Isa Brown hybrid and New Hampshire breed) on the cholesterol content in eggs. On seven occasions during the one-year production cycle (24, 32, 40, 48, 56, 64 and 72 weeks hen's age), 15 eggs from all four experimental groups...

The focus of the research was to examine the effects of the addition of different concentrations of bee pollen to broiler feed on production performance, microbiological composition of caecum and carcass quality. The study was performed on 1200 chickens divided into 5 groups with 6 replicates per group. During the test, the broilers were fed with t...

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 t...

The aim of this study was to evaluate the effect of rearing systems and genotypes on production performance and egg quality. Isa Brown and New Hampshire genotypes were used in this study. These two genotypes were housed in floor and organic rearing systems. During the experimental period, which lasted one year (52 weeks), the following production p...

Intensive broiler chicken production involves different lighting regimes, which affects a natural cycle of secretion of melatonin, a hormone included in multiple physiological processes in a bird's body. This research aimed to determine the effects of dietary melatonin supplementation during the first two weeks of broiler chickens' life, bred under...

The aim of this study was to determine the eggs and eggshell quality of organic laying hens at different stages of the one-year production cycle. Based on the results of these studies, it can be concluded that the organic eggs of 24-week-old Isa Brown layers had lower weight and a higher shape index than the eggs of 48- and 72-week-old hens. On the...

The effect of supplemental protease (Ronozyme ProAct) in broiler diet on the weights and percentage yields of slaughter by-products of male and female medium-growing Master Gris broiler chickens was analysed. Fattening period lasted for 63 days. Broilers were assigned to 3 experimental groups, each consisting of 100 birds. Experimental groups diffe...

In less intensive production systems, native poultry breeds can be used in order to diversify the products and achieve self-sustainability of these breeds through production. Given the missing data on the sustainability of quality of eggs obtained from indigenous, native hens, during storage, the aim of the study was to determine the most important...

The comparison of physical quality properties of table eggs of commercial hybrid Tetra SL and two native indigenous breeds of hens, Banat Naked Neck and Svrljig hen, was performed in conditions of alternative production in the pasture system in portable cages without the floor. The experiment was conducted during the vegetation period, at the age o...

A comparative study of production traits was performed between COBB 500 broilers from a 52-week-old breeder flock and a ROSS 308 from two breeder flocks of different ages (52 weeks and molted flock 79-week-old) in equal, relatively suboptimal ambiental (temperature oscillations) and nutritional conditions (market feed of average quality). The exper...

The aim of the survey was to determine how the egg production sector is complying with animal welfare legislation, which requires a ban on conventional cages and the transition to permitted systems for rearing laying hens - enriched cages and alternative systems, as well as the attitudes of egg producers and consumers on the impact of permitted sys...

The study objective was to examine the effect of the addition of different concentrations of a mixture of three plants (garlic, mint and rosemary) in the diet of broiler chickens on production and slaughter results. The mixture was formed by grinding plants after drying and mixing them in a ratio of 1: 1: 1. The experiment was performed on 600 chic...

In this study, a total of 30 poultry (chicken and laying hens) feed samples collected from different poultry farms in Serbia in 2016 were tested for fungal and aflatoxin contamination. Using the plate count and standard mycological methods, total fungal counts and potentially toxigenic fungal genera were determined. Natural occurrence of aflatoxin...

The possibility for use of high light intensity in broiler production management to improve the health of broilers' legs was examined in a study aiming to determine the effect of two levels of light intensity in different stocking densities of broiler chickens. The study was carried out on 1200 Ross 308 broilers according to a random block system w...

The aim of this study was to compare the effect of two alternative rearing systems (floor and organic) on egg quality traits of New Hampshire laying hens in three different phases of the productive cycle (32, 48 and 72 weeks of age). Egg samples (15 eggs per group) were analysed for quality (egg weight, egg shape index, albumen height, Haugh unit,...

Pulmonary hypertension syndrome or ascites is a complex problem in poultry production. This disease has multiple causes, including genetic factors (genotype, sex) and non-genetic factors (altitude, improper egg incubation, ambient conditions in the poultry house, diet, etc.). Results from numerous studies have shown that improper diet and its inter...

In order to examine the attitude of egg consumers about the poultry welfare and their willingness to spend more money to buy eggs produced in accordance with animal welfare principles, 529 consumers were surveyed in three regions of Serbia (Belgrade, region of Šumadija and Western Serbia and South and Eastern Serbia region). Through the survey ques...

The aim of this study was to investigate the effects of the supplementation of different concentrations of rosemary in broiler diets from day 1 to 42 on growth performance, carcass quality, and cecal microbiological composition of chickens. The research was carried out with 1200 Ross 308 chickens, divided into 4 groups with 6 repetitions per group....

The aim of this study was to evaluate the effect of hen's age and season on production performance and egg quality of laying hens from three different rearing systems. The tested rearing systems were: cage, floor and organic (30 birds Isa Brown hybrid per group). Experimental period was divided into four sub-periods (4 seasons per 13 weeks) and wee...

In order to determine the effect of intensity of light and stocking density, as well as the interaction of light intensity x stocking density on body weight and individual carcass traits, an experiment was performed on 1200 broilers of the Ross 308 genotype. The investigated factors were the intensity of light (LI): 20 lx (K) ; 150 lx (O) and stock...

The effect of Eco-fish meal, as an alternative to fish meal, on the production performance of the lambs of the Mis population in the intensive fattening, was investigated. The experiment was carried out on 40 lambs, the average age of 30 days, divided in 2 groups. In addition to mother's milk, the lambs were given a concentrated mixture and a lucer...

The aim of this study was to evaluate the effect of rearing system and hen's age on quality and chemical composition of eggs. The tested rearing systems were: cage, floor and organic (30 birds Isa Brown hybrid per group). Fifteen eggs per group were collected for analyses in each of three phases of the productive cycle (32, 48 and 72 weeks hen's ag...

This study was conducted to evaluate the effect of different feed formulations, fattening period and sex of broiler chickens on absolute carcass conformation measurements (metatarsus length, keel length, breast depth, breast angle and thigh girth) and conformation indices of medium-growing Master Gris chickens. The results showed that, as induced b...

This study analyses the effect of different protein levels in broiler feeds (supplemented with protease) and different lengths of fattening period on some parameters related to dressed carcass quality. Medium-growing Master Gris broiler chickens were used in a fattening trial lasting 63 days. At slaughter, dressing percentages and abdominal fat per...

In order to examine the consumers? attitude towards eggs, 239 respondents in the area of the City of Belgrade were surveyed, and the assessment of the quality of eggs on the Belgrade market was done by examining the quality of eggs in super/hypermarkets. In the survey, consumers expressed their views about the place of purchase of eggs, the criteri...

The aim of this study was to evaluate the effect of rearing system, genotype and hens age on egg weight and eggs components share. The tested rearing systems were the floor and organic, and tested genotypes were Isa Brown hybrid and New Hampshire breed. Eggs were collected for analyses three times in production cycle (32 weeks hens age, 48 weeks he...

The experiment of the supstitution of soybean meal with raw soybean in the final diet was carried out on Hubbard F15 chickens at the age of 35-42 days. The effect of different levels and varieties of raw soybeans in diets on carcass conformation and share of major carcass parts was determined in a two-factorial experiment 2 x 5 (2 soybean varieties...

This paper presents research results on the effect of protease on the dressing percentage of conventionally dressed carcass and body conformation in broiler chickens. Broiler diet was supplemented with 0.2% protease (group E-I) and 0.3% protease (group E-II), and protein content in the feed was reduced by 4% (E-I) and 6% (E-II) through a decrease i...

To investigate consumers’ attitudes towards a balanced diet and eggs as foodstuff, 509 consumers have been surveyed. Through this survey, the consumers answered questions about the importance of a balanced diet, importance of having eggs in diet, the most common way of egg consumption, benefits and drawbacks of eating eggs. The responses were analy...

This study evaluates the effect of different crude protein levels in broiler diets supplemented with 0.2% and 0.3% protease enzyme (Ronozyme Pro Act) on dressed carcass weight and dressing percentage during two fattening periods (49 and 63 days). The fast-growing strain Cobb 500 was used. At the end of the fattening trial i.e. at 49 and 63 days, 10...

The aim of this paper was to estimate the effect of rearing systems (floor and organic) on the chemical composition of meat of laying hens. The tested genotypes were Isa Brown hybrid and dual purpose breed New Hampshire. Based on the results of this research can be concluded that the rearing system, generally, did not caused statistically significa...

The aim of the present study was to determine the effects of breed (Naked Neck – NN – and Lohmann Brown – LB), age (46 to 49 weeks) and the time of day of sampling (morning eggs – M – and afternoon eggs – A) on the proximate and fatty acid composition of whole eggs. Eggs of commercial hens (LB) had significantly (P < 0.001) less fat, ash and prote...

The aim of this study was to define the conditions for improving broiler leg health, thus ultimately promoting broiler welfare and greater economic efficiency of production, by investigating the effects of litter type, lighting program, or genetic predisposition on the incidence and severity of footpad dermatitis and hock burns. The study was condu...

Fifty–two (26 males and 26 females) week old broilers were examined for carcass fat characteristic. The phenotypic correlation coefficients between abdominal fat and other traits were: 0.65 – left external sartorial; 0.51 – right external sartorial fat; 0.65 – total external sartorial fat; 0.51 – left internal sartorial fat; 0.46 total internal sar...

In this study, a total of 41 poultry (chicken and laying hens) feed samples collected from different farms in Serbia in the beginning of 2014 were investigated for total fungal count, presence of potential toxigenic fungi and natural occurrence of T-2 toxin. The number of total fungi was determined using the plate count method whereas T-2 toxin was...

Alternative laying hen rearing systems have been rapidly introduced into poultry production in an effort to harmonise poultry health and welfare with consumer, producer, industry and environmental demands. They are an integral part of modern egg production. Husbandry systems for keeping laying hens have an impact on, inter alia, the chemical compos...

Laying hen rearing systems have been the focus of scientific research for many years. Over the last few decades, new laying hen rearing systems have been rapidly introduced in an effort to harmonise poultry health and welfare with consumer, producer, industry and environmental demands. Given the above situation, the subject matter of this paper was...

High market demand for high-quality chicken paws, as well as their role in the assessment of the welfare of broiler chickens are the main reasons for the research in this area. In order to determine the effects of rearing system and the body weight of moderate growing broilers on the frequency and severity of incidence of footpad dermatitis, experi...

The aim of this study was to determine the biochemical properties of Streptococcus suis strains isolated from healthy and deceased pigs. For this research we tested 34 S. suis strains isolated from deceased pigs that had clinical signs of septicemia and meningitis, as well as from clinically healthy pigs. The strains that have been already confirme...

The study was conducted on Isa Brown hybrid hens at the age of 49-57 weeks. The effect of using different levels of share of raw soybean of two varieties in mixtures for feeding hens on egg production, body weight, food consumption, the occurrence of defective eggs, mortality and the relative weight of the pancreas was studied. The possibility of r...

Total fungal count, the presence of potentially toxigenic fungi and natural occurrence of ochratoxin A (OTA) were studied in 30 poultry feed samples (14 samples of feed for chickens and 16 samples of feed for laying hens), which were collected from different farms in Serbia at the beginning of year 2014. The total number of fungi was determined by...

The aim of this study was to investigate the effect of conformation of chickens of different genotype on the yield of breast meat. As a typical example of the chickens of very poor conformation pure breed Naked neck chickens were taken, fattened 8 and 10 weeks (groups K 8 and K 10). As an example of good conformation, an imported hybrid of chickens...

Enzyme supplementation of poultry diets is nutritionally, economically and environmentally justified. Enzymes are used to increase the energy value of feed ingredients and enhance the utilisation of protein, fats, carbohydrates and phytin phosphorus from plant materials, leading to a lower excretion rate of undigested nutrients into the environment...

The aim of this study was to investigate the effects of soybean, flax and rapeseed oil on productive performance and carcass quality of broilers chickens. At the beginning of the experiment six groups of 40 one day-old chicks, hybrid line Cobb 500 was formed, with five replications. For nutrition two feed mixtures were used. During the first two we...

The study was conducted with the purpose of the comparative analysis of production performance and carcass quality of two coloured broiler genotypes of differentiated genetic potential for growth (Redbro and Redbro Naked Neck) in conditions of intensive feeding, as well as determining the effect of housing system (free range and poultry house) on f...

Chicken meat from intensive broiler production have different quality compared with meat from native chicken breeds and chicken from a free range production system. The aim of the present study was to evaluate differences in fatty acids content of meat of Naked Neck chickens rared in free range system and two commercial broiler breeds (Cobb 308 and...

This paper investigates the effect of soybean, flax and rapeseed oil on productive performance and lipid fatty acid composition of broiler chickens. Six groups of 40 one day-old chicks hybrid line Cobb 500, with five replications were formed. Three mixtures with 21, 20 and 18% protein were used. The first 14 days groups were fed with the starter mi...

Egg producers in the EU had more than a decade to adapt to Directive 1999/74/EC which prohibits keeping laying hens in battery cages after 2012. Meanwhile, numerous studies have been conducted in order to assess the socio-economic implications of this ban and to evaluate consumers’ willingness to support improvement in layer welfare by paying a hig...

The aim of this work was to evaluate production traits, egg quality parameters and welfare indicators of two strains of layers (Hisex White and Hy Line Brown) kept in different housing systems. In each housing system both strains of layers were housed and that made 6 treatments in 2 x 3 factorial design (2 genotypes x 3 cage types). A) conventional...

Shell breakage (6-20%) is of major concern for its economic consequences and safety of egg consumption. A great deal of effort in the fields of nutrition, genetics and enviromental conditions have been carried out to improve eggshell quality but understanding the formation of the eggshell fabric and the origin of shell defects is perhaps the key to...

In this paper the effect of extruded rapeseed meal on the performance and sensory quality of the breast meat of broilers was investigated. The experiments were performed with hybrid line ROSS 308. The control group was fed soybean meal, and two levels of extruded rapeseed meal were added in experimental groups, 4% and 8% during a period of 42 days....

The use of betaine can influence the resistance, production performance and quality of broiler carcass, and potentially it can reduce the need for choline and methionine in food due to the mutual correlation of these three substances in the organism. Objective of the paper was to investigate the effect of full substitution of added DL-methionine wi...

In the present experiment, the presence of mycological agents in chickens with skin lesions on foot pads was investigated, in order to improve the health of broiler chickens. Foot-pad dermatitis (FPD) is described in the literature as dermatitis caused by multifactor causes. The presence of irritating chemical substances in the litter, genetic pred...

Carcass conformation is a very important parameter in assessing the overall appearance and meatiness of broilers. This study evaluates the effect of protease supplemented to reduced protein diets on production traits, dressed carcass weight and conformation measures in fast-growing Cobb 500 and slow-growing Master Gris broilers over a fattening per...

Light program and quality of litter are important for forming of the environment and have a direct impact on the performance and welfare of broilers. In conditions of short-photoperiod, the welfare of broilers is improved, but they lead to reduced body mass. In this sense, the aim of this study was to investigate the effects of two light programs a...

Nutrition factors are considered to be very important for incidence of foot-pad dermatitis through the effect on the quality of litter. Objective of this study was to investigate the effect of the use of two feeding programs for broilers available on the market and declared in the nutritional/economical sense as standard and economical, on quality...

Requirements for improvement of broiler welfare have initiated certain changes in rearing and management conditions in conventional broiler production, with emphasis on stocking density and duration of photo period. Experimental study was conducted on broilers of fast growing genotypes reared in floor system. Two stocking densities were applied: 12...

Stocking density is considered one of the most important factors for the welfare of broilers. This paper is continuation of the study in order to obtain full evaluation of the impact of different broiler stocking densities on production performance, condition of the broiler legs and body feathering, as welfare indicators but also indicators of the...

Objective of the research was to investigate the effect of genotype on production and slaughter properties of broiler chickens. The usual technology of broiler production was implemented, therefore fattening lasted 42 days. Trial included total of 2070 broiler chickens of following hybrids: Cobb 500, Ross 308 and Hubbard Classic. Chickens of genoty...

Alternative (non-conventional) poultry housing systems are introduced into production, on the one hand for the benefit of poultry welfare and, on the other hand because of the quality of eggs, i.e. the association/correlation between quality of life of hens and quality of product is established. Data obtained in the comparative analysis for proxima...

Calcium metabolism (Ca) in layers depends on many factors which can be divided into factors influencing the intake, absorption, retention and/or excretion of Ca. Varying of any of above mentioned factors presented and reviewed in this study, exhibit their impact on quality of bones in layers and egg shell quality. For the purpose of maintaining of...

The upcoming ban on cage rearing system, ecological aspects of production, perception of better quality and biological safety of products from less intensive systems are reasons in favour of alternative (non-conventional) systems of production of table eggs. Considering only few studies have dealt with quality properties of eggs obtained from autoc...

A 16-week-long experiment was performed to compare the effect of sodium selenite (SS) and selenium-enriched yeast (SY) supplementation on eggshell quality and also to evaluate breaking force correlation with other parameters of shell quality originating from hens fed with selenium supplementation. One hundred Shaver 579 hens (27 weeks old) with sim...

Significance of stocking density in broiler production i.e. production performance, vitality and health condition of chickens, was established at the beginning of development of industrial poultry production. However, considering intensive development of selection work and creation of more productive genotypes which, at the same time, were more dem...

In broiler production, stocking density, i.e. floor surface per chicken, is very important welfare factor which directly and indirectly influences and determines the level of growth of chicken body weight, but it is also related to other welfare indicators. Objective of the paper was to define the broiler welfare in different stocking densities by...

Objective of the research was to establish the growth of body mass and slaughter characteristics of the autochthonous chicken breed - naked neck of different varieties (white, black, gray) in our country, reared in extensive system. Fattening lasted 98 days (14 weeks). In the paper, the growth of body mass of chickens at the age of 8, 10, 12 and 14...

Investigation was carried out on 500 Arbor Acres and Redbro chickens. First group of 30 male and female chickens per genotype was slaughtered after 12 h period of food deprivation. Second group remained in the facility and was fattened until 50. day. Third group was reared for 50 days but in a semi intensive system, with use of 20 m² and free range...

In the latest research relating to mineral nutrition of poultry, the interest in several nutrients is prevailing for which in ordinary diets additional sources are necessary. In mineral nutrition of layers constantly the calcium (Ca) requirements are reviewed as one of the most important factors influencing the quality of eggs and bones, in regard...

Research was carried out on chickens of four genotypes: two slow-growing genotypes, Master Gris (MG) and Farm Q (FQ), one fastgrowing, Hubbard Classic (HC) and one medium-growing Red Bro (RB). To the age of 3 weeks, chickens were reared according to all technological norms for intensive production. After that period, chickens were moved and fatteni...

One hundred male and one hundred female broiler chicks from different strains : Master Gris, Red Bro, Farm Q and Hubbard Classic, were reared in conventional broler house system, during first three weeks After the third week, fattening was continued in an extensive free-range rering system. At the end of experimental period (91 days of age) 10 male...

Production of poultry meat organized on industrial principles, i.e. in intensive way, is characterized by housing of broilers in closed buildings, often in very high housing densities with completely controlled conditions of environment and nutrition. Objective of the research was to investigate the possibility for improvement of certain slaughter...

Cobb 500 and Hubbard Classic broiler chicks were reared on the floor during seven weeks of fattening. Chicks, of each strain, were divided in two groups (160 chicks in group) and feed with two isocaloric diets differed in protein levels. The contents of crude protein in the diets 1, were 23 % (1-2 weeks of age), 22 % (3. week), 21 % (4 - 6 weeks),...

The review of the latest results in application of enzymes in nutrition of poultry is presented in this paper. Results obtained in application of enzymes in nutrition of chickens and layer hens are presented. Investigations have demonstrated that addition of enzymes to diets in nutrition of fattening chickens resulted in improvement of production r...

The fact that most of consumers according to polls and questionnaires in our country, value the most freshness of eggs, and that at the same time they are not satisfied with it, there is necessity to provide guaranteed fresh eggs of high quality. Similar situation in other countries and cities in Serbia has induced some of producers of table eggs t...

Slow growing chickens of genotype Redbro, were reared in two systems in order to determine the effect of duration of fattening on values of slaughter yields/dressing percentages and shares of main carcass parts. Fattening of chickens in chicken coop to age of 84 days had considerable effect on increase of slaughter yields: "Conventional processing"...

The effect of the rearing system (intensive and semi intensive) and biological factors (genotype, age, sex) on absolute and index values of carcass conformation measures in chickens (metatarsus length, keel length, breast depth, thigh girth and breast angle) was investigated. In the trial Arbor Acres and Redbro chickens were used and duration of fa...