Introduction
Poultry rearing is of enormous importance for economy of most countries, including Serbia (Mitrović et al., Reference MITROVIĆ, TOLIMIR, ŠKORIĆ, ĐERMANOVIĆ and ANOKIĆ2006b). Serbia has a long tradition and favourable conditions for the development of commercial poultry production. According to statistics, Serbia has approximately 0.7 ha of land per resident and has suitable soil and climate for growing corn and soybean which are main energy and protein ingredients in mixed feed for the poultry. However, a prolonged economic crisis in Serbia had a major impact on poultry production. As a result of events in the former Yugoslavia and several years of sanctions, poultry production suffered a major crisis, reflected in commercial poultry production. In 2004, poultry production indicators were at the same level as they had been some 20 years before (Pavlovski and Mitrović, Reference PAVLOVSKI and MITROVIĆ2004). Rodić et al. (Reference RODIĆ, PERIĆ, PAVLOVSKI and MILOŠEVIĆ2010) reported that the poultry production in Serbia accounted for 12% of the total animal production. This proportion grew to 12.6% in 2016 (Annual Statistics Report of the Republic of Serbia, 2016). According to the latest available data (Official Gazette of the Republic of Serbia, 2016), total number of poultry for the year 2015 was 17,450,000 units, which represented an increase from 17,167,000 in 2014. Production of meat amounted to around 86,000 t in 2015, while in 2014 it was somewhat larger - 94,000 t. Meat consumption was 12.12 kg per person in 2015. Egg production in 2015 was approximately 1.7 billion eggs, with average production per laying hen around 202 eggs.
The total number of poultry units in the world is 23 billion, (which equals to three units per person), which is approximately five times more than 50 years ago (FAOSTAT, 2016). Due to the increasing human populations and incomes, as well as urbanisation, poultry meat and eggs demand is continuously growing (Mottet and Tempio, Reference MOTTET and TEMPIO2017). In this context, Alexandratos and Bruinsma (Reference ALEXANDRATOS and BRUINSMA2012) estimate that demand for food of animal origin may grow by 7% between 2005 and 2050. Beef and pork demands is predicted to increase by 66% and 43% respectively, while the largest growth of demand is expected to be for poultry meat at 121% and for eggs at 65%. In the past 50 years, total meat production has grown from 78 million tons in 1963, to 308 million tons in 2015, with an impressive increase from 205 million tons to 319 million tons between 1995 and 2015 (Boleli et al., Reference BOLELI, MORITA, MATOS, THIMOTHEO and ALMEIDA2016). During the past two decades, production of poultry meat increased by almost 108% (Avisite, 2015; SNA News, 2015). Meat production is predicted to double between 2020 and 2022 due to population growth and meat consumption per person. In line with this trend, global consumption of the poultry meat is estimated to reach 128 t by 2020. (OECD/FAO Agricultural Outlook, 2016). Average poultry meat consumption per person is still relatively low. In Asia it amounts to 10 kg per year which is two times less than Western Europe and five times less than North America.
The growth of poultry production in the past period intensified to such an extent that it acquired all characteristics of industrial production. At the same time, experts, particularly ecologists, keep warning of extremely high levels of environmental pollution, listing farming (including animal husbandry), as one of the numerous sources of pollution. Furthermore, activists for animal protection and welfare fervently demand abandonment of cattle and poultry rearing in closed spaces, cages and in restricted and dark places (Mitrović et al., Reference MITROVIĆ, BOGOSAVLJEVIĆ-BOŠKOVIĆ, TOLIMIR and ĐERMANOVIĆ2005a). For all these reasons, poultry production worldwide has undergone significant changes, and clear criteria have been established with the purpose to improve the quality of the products (meat and eggs), guarantee the safety of the food, protect and improve the environment, and ensure animal welfare in line with the relevant ethic norms (Muir et al., Reference MUIR, CHENG and CRONEY2014; Elson, Reference ELSON2012).
Generally speaking, there are three types of poultry housing: extensive, semi-intensive and intensive (Mitrović and Đekić, Reference MITROVIĆ and ĐEKIĆ2013). However, according to Đukić-Stojčić et al. (Reference ĐUKIĆ-STOJČIĆ, PERIĆ and MILOŠEVIĆ2017), a clearly defined ‘ideal’ poultry housing system, i.e one which would satisfy requirements for welfare and ensure guaranteed, economical and profitable production, has not yet been defined in Serbia. Recently, pure breeds (traditional, autochthonous breeds) and their crosses (hybrids to a lesser extent) are being increasingly studied in the context of organic poultry production, particularly in EU countries.
The following paper is a review of results acquired upon analysis of the current state and achievements of the poultry production in Serbia and worldwide, with a particular emphasis on impacts of the rearing system, i.e. housing and fattening on the production and the quality of the poultry meat and eggs and, simultaneously, on the welfare of poultry and environmental protection.
Production of eggs for consumption in different housing systems for laying hens
In Serbia and its immediate neighbours, the most commonly used system for egg production is keeping hens in cages. This system is contrary to legal instructions related to animal welfare and the EU Directive 1999/74/EEC. According to the by-law, i.e. Law on Animal Welfare (2009), in relation to facilities in which animals are kept, raised and traded, the systems of housing, rearing and trading of animals, as well as on the content and system of record keeping (Official Gazette of the Republic Serbia 6/10, 57/14), laying hens may be kept only in furnished cages or in some of the so called 'alternative systems'. The aim of the latter is to provide hens with conditions as similar as possible to those in natural environment. This is to improve animal welfare while productivity and egg quality remain at a high level (Matković et al., Reference MATKOVIĆ, VUČEMILO and MATKOVIĆ2007; Pandurević et al., Reference PANDUREVIĆ, HRISTOV and MITROVIĆ2007). Prior to introducing new (alternative) housing systems, it is important to become well acquainted with the management system and processes (breeding technologies), because they usually imply high risks related to productivity, egg quality and bird health (Tauson, Reference TAUSON2005; Reference TAUSON2012; Elson and Croxall, Reference ELSON and CROXALL2006; Sosnowka-Czajka et al., Reference SOSNOWKA-CZAJKA, HERBUT and SKOMORUCHA2010).
Tauson (Reference TAUSON2012) mentioned that conventional cages have been banned in Europe since the beginning of 2012. However, not all countries have been able to implement this, while some other countries, such as Switzerland, Sweden and Norway abandoned the use of standard cages several decades ago. Elson (Reference ELSON2012) points out that that after 2012 'furnished cages' will become more commonly used than classic conventional cages. The advantages of furnished cages include more space and availability of a type of perch which allows for a wider walking range, although walking still remains more restricted than in free-range systems.
For the time being, keeping laying hens in conventional cages is still allowed in Serbia, however, upon joining the EU, furnished cages, or alternative systems will have to be used for the production of eggs for consumption, in accordance with the Directive 1999/74/EEC. Production levels for laying hens kept in furnished cages can reach the same level as those from hens kept in conventional cages, provided that the cages are built in a functional way and that the rearing technology appropriate for the given hybrid is strictly applied. This was confirmed by relatively recent research conducted by Radović (Reference RADOVIĆ2011) who reported similar production results (laying intensity and egg quality) for laying hens kept in furnished cages and those kept in conventional cages.
Tůmová and Ebeid (Reference TŮMOVÁ and EBEID2003), Guesdon and Faure (Reference GUESDON and FAURE2004), Vučemilo et al. (Reference VUČEMILO, VINKOVIĆ, TOFANT, PAVIČIĆ and HAĐINAC2003), Elson and Croxall (Reference ELSON and CROXALL2006), Matković et al. (Reference MATKOVIĆ, VUČEMILO and MATKOVIĆ2007), Tůmová et al. (Reference TŮMOVÁ, ZITA, HUBENÝ, SKŘIVAN and LEDVINKA2007), Vučemilo et al. (Reference VUČEMILO, MATKOVIĆ, VINKOVIĆ, RADOVIĆ and BENIĆ2008), Tůmová et al. (Reference TŮMOVÁ, SKRIVAN, ENGLMAIEROVA and ZITA2009), Matt et al. (Reference MATT, VEROMANN and LUIK2009) and Radović (Reference RADOVIĆ2011) carried out research on alternative housing systems and productivity and egg quality. Tůmová and Ebeid (Reference TŮMOVÁ and EBEID2003) reported that shell strength, breakage, albumen mass and shell colour indices from hens kept in conventional cages are better than those of hens kept in deep litter system. The same authors reported the total production of eggs, egg mass, and food conversion, to be significantly higher in hens kept in conventional cages than of those kept in alternative system (deep litter system). Tůmová et al. (Reference TŮMOVÁ, SKRIVAN, ENGLMAIEROVA and ZITA2009) studied impact of the genotype (Isa Brown, Hisex Brown, Moravia), housing system (conventional housing on 550 cm2 area, and floor) and egg collection time (at 6, 10, 14 o'clock) on the physical characteristics of eggs. The highest results for egg mass were reported for the hybrid Hisex Brown (62.09 g) at the 6 am collection in the conventional cage system. The highest egg shape index was reported for the same hybrid, but at the 2 pm collection time and on the floor rearing system. Matt et al. (Reference MATT, VEROMANN and LUIK2009) studied the effects of different housing systems (conventional and organic) on the biochemical composition of the Hy Line Brown eggs. They reported a larger percentage of carbohydrates in organic eggs (1.9±0.25) than in the conventionally produced eggs (1.0±0.1), while on the other hand, conventional eggs had a larger percentage of proteins (12.35±0.49), fat (8.88±0.44) and dry matter (23.15±0.23) in comparison to organic eggs (11.9±0.48; 7.94±0.40; 22.6±0.23, respectively). Guesdon and Faure (Reference GUESDON and FAURE2004) examined differences in productivity and egg quality between two different cage systems and reported that the cage type had no effect on the productivity, but in furnished cages, very few eggs hatched in nests, and there was a very large number of cracked and broken eggs. Mortality rates of hens kept in conventional cages was significantly higher (P<0.001) than mortality in furnished cages, while the laying intensity during the production cycle was similar for both groups. Tanaka and Hurnik (Reference TANAKA and HURNIK1992) stated that cage type has no effect on the egg mass which increased with hen age.
Comprehensive research on different housing systems for laying hens (alternative - non-battery, enriched - conventional and enriched - furnished) on productivity was conducted by Elson and Croxall (Reference ELSON and CROXALL2006). This study compared systems used on farms in Great Britain, Germany and Holland, and implemented assessment criteria based on the Swedish poultry welfare monitoring system (Tauson and Holm, Reference TAUSON and HOLM2001; Reference TAUSON and HOLM2002). The experiment included 39 flocks of laying hens raised between 16 and 72 weeks of age, and covered the period of up to 70 weeks of age. Daily food consumption per laying hen in week 35 of age was 116.7 g, and in week 60 was 113.5 g (conventional cages), and 110.9 g and 104.7 g respectively (furnished cages), 142.5 g and 123.1 g respectively in the free-range system. Peak lay for the cage system was reached in week 23 (89%-98%), egg production in the week 70 of age reached 77% and 82%, while in alternative system laying peak was reached around the week 25 of age (72% and 82%), and egg production in the week 70 of age reached 62% and 81%. Between weeks 16 and 70 of age mortality of hens in conventional cages was below 6%, in furnished cages below 8% - with the exception of one flock of hens (14%), while in alternative housing systems mortality rate of laying hens was below 10%, with the exception of one flock (around 16%).
Vučemilo et al. (Reference VUČEMILO, VINKOVIĆ, TOFANT, PAVIČIĆ and HAĐINAC2003) pointed out that alternative (aviary) systems are acceptable from the animal welfare perspective, however, they are not satisfactory from the hygiene point of view because of the higher number of soiled and broken eggs and increased risk of diseases. Radović (Reference RADOVIĆ2011) recorded 260 eggs produced per laying hen during one production cycle in the conventional system, and total mortality of 9.5%. In the furnished cage system, 272 eggs per hen were produced during the cycle, and total mortality was 5.8%. In the free-range system, the number of eggs was less, and mortality was higher (around 10%). Results were contrasted against the guidelines of the OIE Terrestrial Animal Health Code, EU directives and the by-law on the minimum conditions for the protection of laying hens, and indicated that, from the production and health standpoints, keeping hens in furnished and conventional cages is more effective than free-range, but from the welfare aspect, it is better to keep them in furnished cages or in free-range. Similarly, Senčić and Butko (Reference SENČIĆ and BUTKO2006) conducted research with two groups of the Lohmann Brown hybrid hens. The control group was kept in conventional (intensive) system, i.e., in cages. The experimental group was kept free-range and had continual access to grass. Egg production of both groups lasted for 52 weeks. The hens from the free-range system laid fewer eggs than those kept in the cage system (266 vs. 295 respectively), consumed more food per day (129 g vs. 115 g respectively), consumed more food per kg of egg mass (2.83 kg vs. 2.35 kg respectively), had higher mortality (6.80% vs. 5.50% respectively). Furthermore, eggs laid by hens from the free-range system had significantly (P<0,01) larger mass (62.40 g and 60.50 g respectively), thicker shell (0.36 mm and 0.34 mm respectively) and more intensive yolk colour (12.00 and 10.00 Roche respectively) compared to caged hens.
Church and Jendral (Reference CHURCH and JENDRAL2005) presented their work on alternative housing systems for laying hens in Holland, Switzerland, Sweden and Germany. Even before the EU Directive (1999/74/EEC) came into force, Holland encouraged farmers to replace conventional cages with alternative systems, such as free-range, deep litter and furnished cages. Besides, the government provides incentives for the programmes promoting and developing organic poultry production. As an EU member state, Holland follows EU directives, and over 50% of their 30 million laying hens are kept in alternative systems. Switzerland passed a federal document in 1978 on animal protection (welfare), created as a guidebook describing correct ways of keeping poultry, including free walking and acceptable (alternative) systems of housing laying hens. In 1981 the Swiss animal welfare agency implemented procedures stipulated by the federal document. According to these, laying hens should be provided with an area of minimum 800 cm2 per bird, a protected place for nesting, and perches. In 1998, Sweden passed a regulation according to which cages must be provided with nests, perches and litter, which aligns with the EU - 1999/74/EEC Directive. Sweden was the first country to use furnished cages in commercial egg production (since 2000). More than 30% of laying hens are raised in furnished cages and over 60% kept as free-range and on deep litter. According to the 2002 amendments to the Decree on the farm animal welfare, keeping laying hens in cages was banned in Germany as of 2007.
Croatia initiated adjustment of farming rules with EU legislation on her way to accession as a member state. Currently, Croatia's regulations on conditions which must be adhered to by farms and animal protection provisions (Official Gazette of the Republic of Croatia 136/05) identifies alternative keeping systems for laying hens. Some researchers in Croatia (Vučemilo et al., Reference VUČEMILO, VINKOVIĆ, TOFANT, PAVIČIĆ and HAĐINAC2003; Senčić and Butko, Reference SENČIĆ and BUTKO2006; Matković et al., Reference MATKOVIĆ, VUČEMILO and MATKOVIĆ2007; Vučemilo et al., Reference VUČEMILO, MATKOVIĆ, VINKOVIĆ, RADOVIĆ and BENIĆ2008; Radović, Reference RADOVIĆ2011; Crnčan et al., Reference CRNČAN, RANOGAJEC and DEŽE2014) have been recently paying special attention to the impacts of the cage system and alternative housing systems, with particular stress on productivity, health and welfare of laying hens and economic viability of each system.
Indigenous breeds are much more convenient for extensive and semi-intensive rearing conditions and, consequently, organic production of meat and eggs. Sorensen and Kjaer (Reference SORENSEN and KJAER2000) studied the potential of traditional breeds for organic egg production in Germany. These authors studied two breeds (New Hampshire and White Leghorn), products obtained by their interbreeding (crossbreds), which tended toward higher egg laying capacity, and line hybrid Isa Brown. The highest egg production from 18 to 43 weeks of age was achieved by Isa Brown laying hens. Mortality of Isa Brown was significantly higher (16%) compared to other traditional breeds and combinations (0.0-1.1%). The assumption was made that it is difficult to achieve high egg production rates while at the same time maintaining good health of hens. The authors concluded that the attempts to create alternative breeds/hybrids have not yet resulted in conceiving an ideal organic hen. Grobbelaar (Reference GROBBELAAR2008) and Grobbelaar et al. (Reference GROBBELAAR, SUTHERLAND and MOLALAKGOTLA2010) studied some productive characteristics of three indigenous South African breeds, Leghorn, and Bare necked hen during a 52 week production cycle. In total, 138.9 eggs with average mass of 55.10 g (bare necked hen) and 279.5 eggs with 60.50 g mass (Leghorn) were produced per housed laying hen.
As in many European countries and elsewhere in the world, most commonly used breeds in Serbia are local (indigenous) hens (Banat Naked Neck, Sombor Crested, and Black Svrljig hen), pure populations of Rode Island, New Hampshire, Amrock, Plymouth Rock breeds, as well as crosses obtained from these breeds (Pavlovski et al., Reference PAVLOVSKI, ŠKRBIĆ, LUKIĆ, KRNJAJA, BIJELIĆ and TRENKOVSKI2010). Tolimir et al. (Reference TOLIMIR, ANOKIĆ, MITROVIĆ, MILOJKOVIĆ and MAŠIĆ1997), Đermanović et al. (Reference ĐERMANOVIĆ, ĐEKIĆ, MITROVIĆ, RAJOVIĆ, MITROVIĆ and PANDUREVIĆ2012), Rakonjac et al. (Reference RAKONJAC, BOGOSAVLJEVIĆ-BOŠKOVIĆ, ŠKRBIĆ, PERIĆ, DOSKOKOVIĆ, PETROVIĆ and PETRIČEVIĆ2017). Mašić and Pavlovski (Reference MAŠIĆ and PAVLOVSKI1994) reported that different housing systems for hens with equal feeding have little effect on the egg quality. However, Pavlovski (Reference PAVLOVSKI1990) presented research results showing substantial advantages for the extensive over the battery system in terms of egg quality, expressed as Haugh units. Some contribution to this subject was given by Tolimir et al. (Reference TOLIMIR, ANOKIĆ, MITROVIĆ, MILOJKOVIĆ and MAŠIĆ1997) who studied internal and external egg characteristics of some indigenous hen populations from eastern Serbia. They reported that the internal and external egg characteristics of indigenous breeds were significantly different compared to data pertaining to the hybrid laying hens used in industrial egg production. Đermanović et al. (Reference ĐERMANOVIĆ, ĐEKIĆ, MITROVIĆ, RAJOVIĆ, MITROVIĆ and PANDUREVIĆ2012) published a detailed report with results of a comparative study of the productive and reproductive characteristics of two breeds (New Hampshire and Sombor Kaporka) hen which are raised in Serbia in large numbers. These breeds are raised in semi-extensive housing systems and demonstrated satisfactory productive and reproductive characteristics suggesting that both breeds can be effectively used in organic poultry production. Rakonjac et al. (Reference RAKONJAC, BOGOSAVLJEVIĆ-BOŠKOVIĆ, ŠKRBIĆ, PERIĆ, DOSKOKOVIĆ, PETROVIĆ and PETRIČEVIĆ2017) conducted a study on the effects of the housing system (floor and organic), genotypes (Isa Brown and New Hempshire) and hen age on egg mass and share of the basic egg parts. Egg mass increased with hen's age, and share of albumen and yolk was significantly affected by the housing system, genotype and hen's age (P≤0.05). In comparison to organic hens, those kept on the floor laid eggs with smaller relative levels of albumen and larger share of yolk (P≥0.05). The eggs of the New Hampshire hens had a smaller share of albumen and a larger share of yolk compared to the Isa Brown genotype (P≥0.05). Yolk share increased and albumen share decreased with hen's age.
Meat production in different housing systems of broilers
In contrast to the industrial fattening of the broiler chicken, nonindustrial production of broilers in the EU countries implies chicken fed with special feed and kept in different extensive systems (in barns, free-range, traditional free-range, unlimited free-range and organic production).
Mitrović et al. (Reference MITROVIĆ, LATINOVĆ and ĐERMANOVIĆ2006a) reported that protraction of the fattening duration from 44 to 62 days resulted in higher final body mass, better FCR and mortality of the broiler chicken, while decreasing the daily growth and the production value index. Calculation of the phenotype correlation coefficients supported this conclusion. In a similar manner, results obtained by Mitrović et al. (2004; Reference MITROVIĆ, ŠKRBIĆ, BOGOSAVLJEVIĆ-BOŠKOVIĆ, OSTOJIĆ and ĐERMANOVIĆ2005b; Reference MITROVIĆ, LATINOVĆ and ĐERMANOVIĆ2006a; Reference MITROVIĆ, PUPAVAC, ĐERMANOVIĆ and OSTOJIĆ2010a; Reference MITROVIĆ, ĐERMANOVIĆ, RADIVOJEVIĆ, RAJIĆ, ŽIVKOVIĆ, OSTOJIĆ and FILIPOVIĆ2010b), Đermanović and Mitrović (Reference ĐERMANOVIĆ and MITROVIĆ2004), Pandurević (Reference PANDUREVIĆ2008), demonstrated that the protraction of the fattening duration results in increase of the final body mass, some slaughter parameters remain practically unchanged, while FCR and mortality increased. This lowered the profitability of the broiler chicken fattening, i.e., the production value index.
As in the egg production context, numerous authors investigated options of using pure, autochthonous breeds, as well as hybrids (slow-growing and fast-growing) reared in different housing systems for the purpose of organic meat production and in line with EU directives for organic poultry production. The aim of the research carried out by Pavlovski et al. (Reference PAVLOVSKI, ŠKRBIĆ, LUKIĆ, VITOROVIĆ, PETRIČEVIĆ and MILOŠEVIĆ2009) was to determine the growth of the body mass and slaughter characteristics of the Naked Neck chicken of different strains (white, black, grey), raised in Serbia, and Farm Q hen which is a French hybrid of the Naked Neck hen, fattened from day 91 to day 98 of age, in extensive systems. Bogosavljević-Bošković et al. (Reference BOGOSAVLJEVIĆ-BOŠKOVIĆ, MITROVIĆ, DJOKOVIĆ, DOSKOVIĆ and DJERMANOVIĆ2010) studied slaughter characteristics and the chemical composition of the hybrid Hybro G broiler (fast-growing) meat, which were fattened to day 56 of age in two different housing systems (‘extensive indoor’ and ‘free range’). In addition, Bogosavljević-Bošković et al. (Reference BOGOSAVLJEVIĆ-BOŠKOVIĆ, MITROVIĆ, PETROVIĆ, ĐOSKOVIĆ and DOSKOVIĆ2008a; Reference BOGOSAVLJEVIĆ-BOŠKOVIĆ, MITROVIĆ, RADOVIĆ, DOSKOVIĆ and ĐERMANOVIĆ2008b) studied the chemical composition of the meat from chickens raised exclusively in barns and in the free-range system. Results indicated that the free-range system was more favourable in terms of higher protein and lower fat in both white and dark meat of the chicken, with higher levels of fat and slightly lower proteins observed in the meat of females. In a similar manner, Mitrović et al. (Reference MITROVIĆ, ĐERMANOVIĆ, PUPOVAC, OSTOJIĆ and RAJOVIĆ2011a; Reference MITROVIĆ, BOGOSAVLJEVIĆ-BOŠKOVIĆ, STANIŠIĆ, DJERMANOVIĆ, DOSKOVIĆ and RAKONJAC2011b; Reference MITROVIĆ, OSTOJIĆ, DJERMANOVIĆ, PANDUREVIĆ and JEŽ2011c; Reference MITROVIĆ, BOGOSAVLJEVIĆ-BOŠKOVIĆ, DJERMANOVIĆ, PERIĆ, JOKIĆ and PANDUREVIĆ2012) carried out a parallel study of fattening and slaughter characteristics of two domestic strains (White Naked Neck hen and Black Svrljig hen) fattened in semi-intensive system until 84 days of age for the purpose of organic meat production. At the end of fattening period, the broilers of both sexes of the White Naked Neck strain had statistically significantly larger (P<0.05) share of thigh and drumstick (34.29 vs. 33.93%), and smaller share (P<0.01) of the back and pelvis (26.34 2 vs. 6.97%), while the body weight was insignificantly larger (1587.07 vs.1562.28 g), and the yield of the ready-to-roast carcasses was similar (61.73 vs. 61.99%). Besides, the authors reported larger live mass, processed carcasses, head, neck, back and pelvis share, thigh and drumstick, legs and internal organs (stomach, heart, liver) in male units, while the female units had larger relative share of processed carcass, breasts, wings and abdominal fat.
Many authors have conducted research with an aim to identify the most suitable breed, strain or hybrid for organic production of the poultry meat in a particular housing system accompanied with adequate nutrition and optimal duration of the fattening period. Van Marle-Köster and Webb (Reference VAN MARLE-KÖSTER and WEBB2000) studied characteristics of six native lines, including Bare neck breed and one commercial hybrid (Cobb), fattened to 77 days of age. Sabbioni et al. (Reference SABBIONI, ZANON, BERETTI, SUPERCHI and ZAMBINI2006) examined yield of carcasses and breasts, thighs and drumsticks share of male commercial hybrid (Hy-Line W 36), fattened in open (4 m2/laying hen) to around 210 days. Body weight ranged between 2142 g and 2212 g, yield of carcasses between 62.07% and 63.33%, breasts between 14.97% and 15.20%, and the share of thighs and drumsticks ranged from 33.0% to 34.0%. Significantly lower weight in the case of the Italian breed Robusta maculata (1,670 g) was reported by Castellini et al. (Reference CASTELLINI, DAL BOSCO, MUGNAI and BERNARDINI2002a) for the 81 days of fattening. Grashorn (Reference GRASHORN2006) studied two slow-growing (Isa S 457 brown feathered and Isa J 957-white) and two fast-growing strains (Hubbard JV-white and Ross 308-white) fattened to 84 days of age. Faria et al. (Reference FARIA, BRESSAN, DE SOUZA, ROSSATO, BOTEGA and DA GAMA2010) examined carcass characteristics of male and female broilers of two strains (P. Pedres and P. Pelado), slaughtered at the age of 65, 75, 85 and 95 days and raised in semi-extensive systems, while Castellini et al. (Reference CASTELLINI, MUGNAI and DAL BOSCO2002b) studied effects of two fattening systems (conventional and organic) on the yield of carcasses and meat quality of the Ross hybrid male broiler chicken, fattened from 56 to 81 days of age. Additionally, noteworthy research was conducted by Lichovníková et al. (Reference LICHOVNÍKOVÁ, JANDÁSEK, JŮZL and DRAČKOVÁ2009) who offered a comparative presentation of the fattening and slaughter results of two genotypes of male chicken - Isa Brown (slow-growing) and Ross 308 (fast-growing), grown until day 90 of age.
Mikulski et al. (Reference MIKULSKI, CELEJ, JANKOWSKI, MAJEWSKA and MIKULSKA2011) studied fattening and slaughter characteristics of the slow-growing - SG (Hubbard JA957) and fast-growing - FG (Hubbard F15) hybrids kept in closed housing (I), and in free-range (O) fattened until 65 days of age. At slaughter weight, body weight of the slow-growing hybrid (SG) raised in a closed housing and the one raised in free-range was equal (3.64 kg), while the mass of the fast growing (FG) hybrid was similar (O - 4.40 kg, I - 4.41 kg) in both systems. Housing system (fattening) made no impact on the final body mass of either genotype. However, slow-growing broilers had insignificantly smaller slaughter yields; ready to roast (SG-76.02% and FG-76.42%), and significantly smaller (P<0.05) breast musculature (SG-23.13% and FG-24.73%), thighs (SG-9.83% and FG-10.16%), as well as drumstick musculature (SG-13.76% and FG-14.89%). Furthermore, meat from free-range chickens (O) was of darker colour (breast and drumstick), had higher level of protein in the breast (O-24.73% and I-23.79%), and drumstick (O-19.43% and I-19.01%), as well as better water binding capacity, than the chicken raised in a closed housing (I). The meat of the broilers raised in free-range had lower levels of fat in breast (O-0.82%, I-1.14%) and drumstick (O-7.22%; I-7.56%) than the meat of the broilers raised in closed housing, and for this reason was less juicy. Sirri et al. (Reference SIRRI, CASTELLINI, BIANCHI, PETRACCI, MELUZZI and FRANCHINI2011) conducted an in-depth analysis of the production of organic poultry meat, in line with the EU legislation (Council Directive 1999/74/EC), of three hybrids (strains) - Cobb 700 (FG), Bare neck hen (MG) and Brown Classic Lohmann (SG). The duration of fattening was 81 days (FG and MG), and 96 days (SG). The fattening of the Brown Classic Lohmann (SG), which is also used for egg production, was extended for 15 days in order to achieve final body mass appropriate for the market. The genotype selection in organic production had significant impact on slaughter values and meat characteristics (final body mass, processed carcass mass, slaughter weight, yield and share of the main parts, pH, colour, drip loss, cook loss, and collagen share) and the chemical composition of the breast and drumstick meat. Finally, it was generally concluded that the genotype had significant impact on the functional (organoleptic) characteristics and nutritional value (chemical composition) of the meat.
Conclusions
Poultry production in Serbia has fluctuated in the recent past for several reasons. On a global level, poultry production in the world and EU countries in the past two decades was marked by changes instigated by the consumers. In line with the consumers' requests for the food to be not only cheap and tasty, but also ecologically acceptable and safe, it became imperative to ensure environmental protection as well as poultry welfare. This was achieved by respecting clearly defined legal regulations (directives and regulations) and application of relevant international standards (HACCP, ISO). EC Directive 1999/74/EEC stipulating minimum standards for protection of laying hens kept in cages banned further investing into new conventional systems after year 2003 and prohibited their use after 2012.
In Serbia, according to the law on animal welfare (2009) stipulating space and furnishing of the space intended for keeping, raising and trading animals for production, systems of keeping, breeding and trading particular types and categories of animals, as well as the content and method of record keeping (Official Gazette of the Republic of Serbia 6/10, 57/14), laying hens can only be kept in furnished cages or one of the so-called alternative systems.
Many authors have investigated the options of using pure, autochthone breeds, as well as hybrids (slow growing and fast growing) bred in different systems for the purpose of organic meat production and in line with EU directives for organic poultry production. Although there is increased interest in breeding autochthone poultry breeds and strains in order to maintain them and include them in organic broiler meat production in semi-intensive, semi-extensive and extensive systems, not many studies have dealt dealing with this issue, i.e. management systems in relation to poultry meat production, have been published in Serbia (in contrast to developed countries, particularly EU members).
It can be concluded that the poultry production in Serbia should evolve towards its inclusion in the global trends which are defined by consumers' request; product quality, new EU regulations (poultry welfare) and environment protection. Current problems need to be solved by conducting an in-depth comprehensive analysis which will serve as a basis for short term and long-term strategies. Programmes should be developed to replace the current spontaneous poultry production with a clearly defined planned production, while investigating options for development of other branches of poultry breeding and organic production. Harmonisation with EU regulations should be carried out in a comprehensive manner, with scientific and expert analysis of the possible impact of the implementation of this regulation in the context of our conditions. It is important to raise awareness of the health and safety of the products, which should be achieved by permanent education of both producers and consumers. Adhering to above requirements will ensure successful development of egg and poultry meat production in Serbia.
