ISSN 1313 - 8820Volume 6, Number 1

March 2014

2014

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Tsanko YablanskiFaculty of AgricultureTrakia University, Stara ZagoraBulgaria

Co-Editor-in-Chief

Radoslav SlavovFaculty of AgricultureTrakia University, Stara ZagoraBulgaria

Editors and Sections

Genetics and Breeding

Atanas Atanasov (Bulgaria)Nikolay Tsenov (Bulgaria)Max Rothschild (USA)Ihsan Soysal (Turkey)Horia Grosu (Romania)Bojin Bojinov (Bulgaria)Stoicho Metodiev (Bulgaria)

Nutrition and Physiology

Nikolai Todorov (Bulgaria)Peter Surai (UK)Zervas Georgios (Greece)Ivan Varlyakov (Bulgaria)

Production Systems

Dimitar Pavlov (Bulgaria)Bogdan Szostak (Poland)Dimitar Panaiotov (Bulgaria)Banko Banev (Bulgaria)Georgy Zhelyazkov (Bulgaria)

Agriculture and Environment

Georgi Petkov (Bulgaria)Ramesh Kanwar (USA)Martin Banov (Bulgaria)

Product Quality and Safety

Marin Kabakchiev (Bulgaria)Stefan Denev (Bulgaria)Vasil Atanasov (Bulgaria)

English Editor

Yanka Ivanova (Bulgaria)

2014

ISSN 1313 - 8820 Volume 6, Number 1March 2014

Review

Blue-green coloured eggs in Gallus gallus domesticus

H. Lukanov*

Department of Animal Science – Nontruminant and other Animals, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria

Abstract. Chicken eggs with blue-green coloured eggshells have been known for centuries. The pigmentation is due to deposition of biliverdin IX and biliverdin zinc chelate in eggshell and underlying membranes during their formation. The deposition of pigment is determined by a dominant autosomal gene, marked with О. According to most recent research, the gene responsible for this mutation is SLCO1B3. In the world, there are some breeds and breed groups of chickens that lay eggs with blue-green eggshells. During the last two decades there has been an increasing interest in non-traditionally coloured eggs in West Europe, North America and Japan. Consequently, some egg-laying chicken strains laying blue-green eggs have been created. All non-purebred and hybrid layers producing blue-green eggs are collectively called Easter Eggers and contribute to the maintenance of biological diversity in domestic chickens.

Keywords: Easter Eggers, egg shell colour, “blue egg” gene, biodiversity, Araucana

AGRICULTURAL SCIENCE AND TECHNOLOGY, VOL. 6, No 1, pp , 20143 - 10

Introduction American chickens is multiple: some phenotype traits have come from birds imported from China while others from Japan, India and the Philippines. Storey et al. (2011) and Crawford (1990) suggested Domestic chickens laying eggs with blue-green eggshells have that ear tufts were a spontaneous mutation of domestic chickens in been known since the Middle Ages. Most probably, the origins of South America. The mystery was finally solved after the discovery of these birds are much back in time. Chickens laying such eggs were

reared by the aboriginal population of South America and Oceania. Today, they are still encountered on this territory under the general name Rapanui/Olmecs.

It is suggested that these attractive birds were brought to South America more than 1500 years ago from southeastern Asia. Proofs for existing contacts between Asia and South America in the Pre-Columbian era are the names of areas similar to Chinese names, similarities in architecture, arts, weapons, religious rituals and language. Three thousand years B.C., the Chinese grew peanuts,

thand people in India – maize during the 12 century, which are native crops of South America (Crowford, 1990). On the other hand, there is evidence about ancient communication between South America and Polynesia islands based on the distribution of the sweet potato in the Pacific region ( Green, 2001;

). The remnants of a big Chinese ship, dating back to 1431, have been discovered around the west coast of South America. Probably, these transpacific communications between Asia and

thSouth America had existed long before the 15 century (Cushing, 2009, Storey et al., 2011). Another possible proof of common origin is the occurrence of domestic chickens laying green eggs in both southeastern Asia (China, Malaysia, Indonesia, Myanmar) and South America and Oceania. Birds with marked fibromelanosis, used in rituals and folk medicine, are encountered on both continents (Johannessen, 1982; Crawford, 1990; Storey et al.,

remnants from plants, domestic and wild animals and chickens in the 2011). Some mutations in domestic chickens as the pea comb, lack El Arenal-1 site, 5 km away from the Chilean coast in the Arauco of tail, frizzle and silky feathering, are specific for Asian and some province (Figure 1), dated back to XI–XV century (Storey et al., African and South American breeds. Other mutations are specific 2007; Storey et al., 2011). The findings included about 83 bones and mainly for European breeds – polydactyly, crests, rosecomb, double bone fragments (Storey et al., 2007; Quiroz et al., 2008, cited by comb –and they were not described in early American flocks Storey et al., 2011). By means of carbon radiolabelling, three of the (Crawford, 1990). According to some authors (Carter, 1998; Pearse bones were dated back to the period between XIV–XV century, i.e. and Pearse, 2010, cited by Storey et al., 2011) the origin of South

Hather and Kirch, 1991; Ladefoged et al., 2005

3

* e-mail: dr_lukanov@abv.bg

Figure 1. Map showing Polynesia and the western coast ofSouth America with the localization of El Arenal-1 (Storeyet al., 2007)

Hawaii

Equator

Easter Island

New Zealand

Vanuatu

Niue

Tonga

American Samoa

CookIslands

El Arenal 1

4

before Europeans came to the continent (Storey et al., 2008a; Iberian domestic chickens, used for fights and as food (Greenlee, Storey et al., 2011). Remnants from domestic chickens were also 1939; Termer, 1951; Carter, 1971). Indians used chickens and their discovered in the Polynesia island, the oldest being found in Vanuatu eggs for religious, but also for commercial purposes instead of and Santa Cruz and dated back to 3100 years ago, as well as in money and gold and for paying taxes to European intruders Samoa and Tonga (2900 years ago) (Beavan-Athfeld et al., 2008; (Crawford, 1990; Storey et al., 2011).Storey et al., 2008a, 2010, 2011). According to some novel The earliest evidence from Europe about hens laying blue-investigations, the origin of chickens reared in South America is green eggs from 1526 is given by the Spanish general and naturalist Polynesia (Storey et al., 2007; Gongora et al., 2008; Storey et al., Cabot (Lukanov et al., 2012). These unique chickens spread from 2008b; Terry, 2011). The facts are supported by contemporary Spain to other countries in Western Europe. In XVIII century, they comparative tests of DNA of ancient chicken relics from Polynesia were described in England and the other Western Europe countries. islands and birds reared there at present. The evidence tracing the The occurrence of chickens of unusual appearance on Spanish pathway of domestic chickens from Asia to the west coast of South ships, laying green eggs was reported by Dutch pirates (Cushing, America is irrefutable and supports the thesis of numerous 2009). The first reports about tailless chickens in Europe are from researchers (Carter, 1971, 1975; Johannessen, 1981, 1982; the same period, as they were probably imported from South Langdon, 1989; Crawford, 1990). America to Europe by Dutch pirates (Storey et al., 2011).

Having studied mitochondrial DNA in domestic chickens and It was in the beginning of the XX century that these hens started red junglefowl, Liu et al. (2006) observed several haplotypes specific drawing attention again. Prof. Salvador Castello Carrera from Spain for Asian chicken breeds. These data and ancient remains from has exhibited them on the First World Poultry Congress held in 1921 domestic chickens in Vanuatu, Samoa and Tonga allowed Storey et in the Hague, Netherlands as „Gallus inauris” (Castello, 1924). The al. (2010) and Dancause et al. (2011) to determine haplogroup E as occasion of the exhibition is his meeting with Dr Bustros in 1914, who specific for Polynesian and Chilean fowl since older times. made exceptional efforts for conservation of indigenous birds reared

th thThere is still no reliable scientific explanation as to how, where by South American Indians by the end of 19 and the early 20 and when the unique egg pigmentation in these chickens appeared century. The birds exhibited at the congress resembled modern and what their origin was (Storey et al, 2011). Two main theories Araucana with three specific traits: green eggs, ear tufts and lack of about the origin of Easter Eggers exist. The supporters of the most tail (Storey et al., 2011). Unlike the Araucana, they had a leaf-shaped popular modern theory based on analytical methods (Borrell, 2007; comb. Dr. Ruben Bustros selected the birds from two native Indian Storey et al., 2007; Gongora et al., 2008; Terry, 2011) affirm that the breeds, part of the breed group Rapanui/Olmec – Collonocas and birds encountered in South America were of Polynesian origin in Quetros. These two sub-breeds were reared by Araucana Indians which the green junglefowl (Gallus varius, Shaw, 1798) is involved. and other related tribes in the territory of Chile and Peru. Collonocas According to the second theory, which is rather of historical laid green eggs and were rumpless, while Quetros had ear tufts significance (Castello, 1921, cited by Cawley, 1979; Punnett, 1933), coded by a lethal gene. Dr. Bustros saw these unique birds during his the chickens laying blue-green eggs were hybrids between pheasants and red junglefowl (Gallus Gallus, Linnaeus, 1758), one part of the progeny was fertile and female crosses laid blue eggs. Later, Castello (1924) suggested that the unique traits of South American chickens were result of breeding ancient South American domestic chickens and chickens of Spanish origin. The most recent studies using weight molecular markers of a part of chromosome I, where the O locus of Chinese Dongxiang and Araucana was base, Wang et al. (2013) affirmed the presence of separate parallel appearance of this mutation on both continents.

Over 16 breeds and breed groups of chickens laying blue-green eggs, possessing unique traits, are known in the world. The conservation of these birds is important for maintaining the global genetic diversity of Gallus gallus domesticus.

History of modern Easter Eggers

The first testimony of chickens laying blue-green eggs dates thback to the early 16 century. Ferdinand Magellan was the first to

describe these birds in 1519 after he got accosted in the Santa Lucia bay on the west South American coast (Cushing, 2009). Latcham (1922, cited by Storey et al., 2011) also provide early facts for the presence of hens, ducks and turkeys in South America land. It is believed that Magellan brought on his ship birds laying blue-green eggs reared by Guarani indigenous people. Upon his return to Spain, the birds were imported to the Old World. Some European

thconquistadors from the early 16 century describe these chickens in the country of contemporary Argentina and Brazil (Nordenskiöld, service at the State Chilean Army in 1880. Later, he brought with him 1922). Later, in 1532, Pizarro told about chickens reared by Indians representatives of these groups and after nearly a decade of in Peru (Storey et al., 2007). On their way back, Spanish and selection (Figure 2), created the birds exhibited by Prof. Castello in Portugal conquistadors brought with them to South America mainly

Figure 2. Mr Ruben Bustros with a Gallus inauris rooster,showing well-developed ear tufts (Castello, 1923)

5

1921. Castello (1924) described three types of chickens, typical for Chile: a Chilean chicken of the bantam type laying blue eggs; a non-rumpless chicken, laying green eggs and a chicken with ear tufts, laying blue eggs only seldom. Latcham (1922) describes a frizzle mutation in Chilean chickens, probably imported by the Portuguese (Storey et al., 2011). The chickens in South America were reared in a semi-wild state almost over the entire continent, without purposeful breeding (Latcham, 1922; Castello, 1924). Dr. Bustros was the only one to put the beginning of selection against the background of theoretical knowledge by the end of 19th century.

thAt the beginning of the 20 century, American selectioners

1933) and ducks (Wang et al, 1995). The mutation was also observed in Japanese quails (Ito et al, 1993). Figure 4 shows the main types of eggshell colours in Gallus gallus species.

Biliverdin IX is a heme derivative, synthesised due to the catalytic activity of heme oxygenase I (HMOX1) and it plays a significant role in systemic biochemical pathways (Lang and Wells, 1987; Zhao at al., 2006; Wang et al, 2011b). In two independent studies, Zhao et al. (2006) and Wang et al. (2009) confirmed the imported from South America birds resembling the chickens presence of high biliverdin and low protoporphyrin levels in the green selected by Dr. Bustros. On the basis of imported birds, the modern eggshell of Dongxiang chickens. Unlike mammals, in birds, fish and breed Araucana was created and named after the eponymous native amphibians, biliverdin is not converted to bilirubin because of the low tribe (Figure 3). Along with the establishment of American activity of biliverdin reductase (Wang et al, 2011b).Araucanas, the Cream Legbar was created in the United Kingdom

The mechanism of deposition of the brown pigment on the basis of birds imported from South America (Lukanov et al., th protoporphyrin in some bird species is explained by Braid et al. 2012). During the middle and the second half of the 20 century, all

(1975). The green colour of the eggshell is due to biliverdin other chicken breeds laying blue-green eggs were founded and deposition by shell glands on eggshell membranes and eggshell established. (Kennedy and Vevers, 1973). According to Wang at al. (2007) the It is generally acknowledged that chickens laying blue-green deposition of biliverdin and protoporphyrin on the shell occurs in a eggs should be termed Easter Eggers. The name comes from the synchronous manner. Kennedy and Vevers (1973) consider the O fact that the representatives of the breed group Rapanui/Olmec gene as a member of a specific enzyme system which catalyses were reared by the indigenous population of the Easter Island in a heme oxidation to biliverdin. Maines (1997) determines heme semi-wild state and corresponds to the modern proofs of their origin.oxygenase (HMOX) as the primary enzyme promoting the conversion of heme to biliverdin, free iron and carbon oxide. The Factors determining the eggshell colourenzyme is encountered under two forms: HMOX1 and HMOX2. Later, Liu et al. (2005) outline heme oxygenase-1 (HMOX1) as a According to Poole (1963), the primary pigments responsible specific enzyme catalysing heme breakdown to biliverdin and thus, for egg colour in wild and domestic birds are protoporphyrin IX, eggshell colouration. These assumptions were affirmed by Wang et biliverdin IX and zinc biliverdin chelate, as later confirmed by al, (2010a) by reporting a significantly higher expression of HMOX1 Kennedy and Vevers (1976) and Ito et al. (1993). Kennedy and in hens laying blue-green eggs compared to those laying brown Vevers (1976) detected also traces of coproporphyrin III.. The eggs. pigments are deposited mostly in superficial eggshell layers (Zhao at

Wang et al. (2013) established that the SLCO1B3 gene (solute al., 2006; Wang et al., 2007). Pigment depositions in eggshells are a carrier organic anion transporter family, member 1B3) was result of heme oxidation products (Wang et al., 2011а). Kennedy and responsible for this specific eggshell colouration. It belongs to the Vevers (1973) found out that Araucana chicken eggshells contained family of organic anion-transporting polypeptides (OATP), acting as biliverdin IX, zinc biliverdin chelate and protoporphyrin IX. Later membrane transporters of organic compounds, including bile salts.more detailed studies in more than 100 avian species have shown

In their studies on the morphology of eggs with green, white and that blue eggs contained only biliverdin IX and zinc biliverdin chelate intermediate colours from domestic Taiwan ducks, Wang et al (1995) whereas the colour of brown eggs was due to large amounts of established significant differences in eggshell structure in the protoporphyrin (Kennedy and Vevers, 1976). Apart from some wilds, different genotypes. Green eggs had a finer shell surface texture, the blue-green egg colouration is reported in domestic fowl (Punnett,

Figure 3. Araucana fowl painting from The NationalGeographic Magazine, April, 1927

Figure 4. Blue-green egg (left) and brown, and white-shelled eggs (right)

6

more compact and fine palisade layer, more regular and smoother mammillary layer. They demonstrated also that green eggs were with thicker shells compared to white eggs. The chemical analysis of eggs showed higher lecithin content and lower cholesterol content in yolks of green eggs.

Genetic features in the inheritance of the green eggshell colouration

Punnett (1933) was the first to investigate the genetic background of green chicken egg pigmentation and to determine its inheritance in an autosomal dominant manner. The gene responsible for this mutation in chickens is called Oocyan (O). It is located in the proximal end of the short arm of chromosome I of fowl genome and codes for the blue-green egg colour (Hutt, 1949; Crawford, 1990; Bitgood et al., 2000; Wang at al., 2011a). Many researchers (Bruckner and Hutt, 1939; Bitgood et al., 1980; Bitgood et al., 1983; Bitgood et al., 2000; Bitgood, 1985; Crawford, 1986) outlined the close linkage of the O gene with the gene responsible for pea comb (P) occurrence or as recently termed – SOX5 (sex

factor which has provoked the appearance of the blue-green egg determining region Y-box 5). Bitgood et al. (1983) and Bartlett et al. phenotype after having studied all 21 single nucleotide (1996) have determined the distance between О and Р to 4.28±1.3 polymorphisms over the entire SLCO1B3 genomic region in cM and 4.5±0.1 cM, and earlier, (1939) Araucana, Dongxiang, Lushi and 9 other chicken genotypes. demonstrated the close linkage of both loci for the first time. Another Homozygous chickens (O*LC/O*LC) had more saturated eggshell gene in close proximity to the O locus is ALEV1 or ev1 (avian colour than heterozygous ones (O*LC/O*N).leukemia endogenous virus element 1) – at a distance of 1.8 сМ and

4.1 сМ between loci О and Р (Bartlett et al., 1996). According to Zhao Biological diversity in poultry farminget al, (2007) two single-nucleotide polymorphisms in the ALEV1

region were associated with the expression of blue-green shell After World War II, high-producing egg laying and meat-type colouration in domestic fowl. Wang at al. (2011а) discovered a

strains almost became largely predominant in productive poultry single nucleotide polymorphism (g.67419892-67419904del13), breeding. For a rather short period of time they replaced the associated to blue-green eggs at a distance of 2 cM from the О locus. purebred lines issued by several chicken breeds (Lalev et al., 2011; Liu et al. (2005) suggested that the gene coding for HMOX1 Nikolov and Gerzilov, 2011; Muir and Aggrey, 2003; Delany, 2004). synthesis was the potential О gene. Despite the production of a Lines descending from two breeds: White Cornish and White much larger amount of HMOX1 with substantially higher activity in Plymouth Rock are the most widely used in industrial broiler chicken chickens laying blue-green eggs (Wang et al., 2011b), the gene production. The leading white egg laying hybrids are obtained on the responsible for the synthesis of the enzyme HMOX1 is found on a basis of White Leghorn highly productive lines. The colourful layer relatively large distance from the О locus, but probably interacts with hybrids based on feather sexing are produced mainly on the basis of the О gene (Wang et al., 2010a).breeding Rhode Island Red sires to Rhode Island White hens Three candidate genes for the expression of biliverdin (Delany, 2006; Davita et al., 2009; Lalev et al., 2012; Lukanov et al., pigmentation of eggshells were outline by Wang at al. (2010b): 2013).SLCO1C1 (solute carrier organic anion transporter family, member

The alarming concentration of global genetic resource 1C1), RECQL (RecQ protein-like) and IAPP (islet amyloid accompanied by the extinction of numerous breeds and breed polypeptide). In a later investigation, Wang at al. (2011a) suggested groups has recently become more and more important (Hammond, the need for a more detailed investigation between the IAPP gene 1994; Delany and Pisenti, 1998; Pisentiand blue-green eggs.

). It should be noted that there is no The first report for an EAV-HP insertion in the SLCO1B3 region established chicken breed laying blue-green eggs which has (solute carrier organic anion transporter family, member 1B3) in two disappeared, on the contrary, their popularity is increasing at a genotypes of Chinese chickens responsible for the blue-green shell global scale. Efforts for preserving the genetic diversity in poultry colouration was made by Wang et al, (2013) and the authors outlined breeding could provide appropriate genetic material for future trends the SLCO1B3 gene as responsible for the mutation. The research in poultry farming ( Notter, 1999; Delany, 2003; Hillel team has studied four candidate genes (SLCO1C1, SLCO1B3, at al., 2003). The global changes of the climate, the altered feed LOC418189 and SLCO1A2) in the О locus, which could determine crops, economic criteria, emerging dangerous diseases in some the expression of the specific eggshell colour in Araucana and areas, the new market requirements related to poultry welfare Dongxiang. This mutation allows the expression of SLCO1B3 in (Council Directive 1999/74/EC) are important prerequisites for a uterine shell glands only in chickens laying green eggs (either homo- serious approach to the problem. One of the essential elements of or heterozygous) but is absent in shell glands of the other modern European livestock husbandry is the welfare of poultry and phenotypes. Figure 5 shows the location of the locus O in the preferential rearing in free-range production systems (Belorechkov, chicken chromosome 1. An interesting fact is the presence of EAV-2010; Gandini et al., 1998; Cassandro et al., 2004; De Marchi et al., HP (chicken endogenous retrovirus elements group) insertion in 2005).both Red Junglefowl and Sonnerat's Junglefowl (Sacco et al., 2001).

In EC member states, the organically produced products are Wang et al. (2013) believe that EAV-HP is the exact mutagenous

Bruckner and Hutt

Barker, 1999; et al., 1999; Ruane, 1999; Delany, 2003

O'Brien, 1994;

Figure 5. Refined localization of O on the chickenchromosome 1 (Wang et al., 2013)

SLCO1C1L1

Physicaldistance (Mb)

0.53

0.53

0.54

0.12

0.75

0.51

0.37

Recombinationfraction

LODscore

0.06 11.62

9.25

10.2615.84

15.84

10.26

11.10

5.27

0.06

0.040.02

0.02

0.04

0.04

0.07

L2

L3L4

L5

L6

L7

L8

SLCO1B3

LOC418189

SLCO1A2

SOX5(pea comb)

evl

O

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gaining increased popularity (Castellini et al., 2008). During the last eggs from happy hens (Van Horne and Bondt, 2003; Van Horne, two decades, the adaptation potential and production traits of 2003; Van Horne and Achterbosch, 2008) would probably raise the different chicken breeds and crosses in free-range systems are interest to eggs laid by Easter Eggers. extensively studied (Barna et al., 1995; Thear, 1997; Duran, 2004; The appearance and maintenance of these breeds and hybrids Beaumont et al., 2004; Sandilands and Hocking, 2012) with regard is a useful trend towards conservation and enrichment of the genetic to organic produce (Krawczyk et al., 2000; De Marchi et al., 2005; diversity of industrial and exhibition poultry framing. An interesting Ferrante et al., 2005; Rizzi et al., 2007; Krawczyk, 2009). fact is that green eggs are preferred to white and brown eggs on the

On a global scale, a lot of chicken breeds and groups laying Chinese market (Wang at al., 2011). Nevertheless, against the blue-green eggs are known – Araucana Standard and Bantam, background of the global poultry meat and egg produce and the British Araucana Standard and Bantam, Cream Legbar, Java leading significance of the economic effect, traditional egg-laying Bantam, Ameraucana Standard and Bantam, Schijndelaar (Figure and meat-type hybrids would be dominating to satisfy the increasing 6), Rapanui/Olmec, Dongxiang (Punnett, 1940; Lukanov et al., demand for cheap poultry products. On the other hand, the studies 2012а; Lukanov et al., 2013), as well as several less popular breeds on the compatibility of some chicken breeds and their crosses, such as Lushi (Wang et al., 2013), Pama, Isbar, Svrljig chicken including those laying blue-green eggs, with industrial production (Lukanov, 2012). During the last years Dongxiang chickens have systems in developed countries or their fitness for use in regions with been used to investigate the intrinsic genetic and biochemical challenging climate, feed availability, epizootic and economic mechanisms of blue-green egg colouration (Zhao, 2006; Wang et conditions, should be encouraged. Despite the increasing al., 2009; Wang et al., 2011; Wang et al., 2013). Apart from this urbanisation on a global scale, the production of poultry products in mutation, the representatives of the aforementioned breeds are also backyards would preserve its importance in the future (Alders and carrying genes determining other phenotype traits such as crests Pym, 2009; Mc Leod et al., 2009). The maintenance of genetically (Cr), polydactyly (Po), ear tufts (Et), beard and muff (Mb), valuable populations is therefore a primary goal for National Gene rumplessness (Rp), fibromelanosis (Fm). This diversity of Funds. genotypes will undoubtedly contribute to the maintenance and enrichment of the genetic diversity in chickens.

In some European countries (United Kingdom and Germany), Conclusionhigh-production layer hybrids have been created with regard to blue-

green egg production: Heritage Skyline (United Kingdom), There is solid evidence for the Polynesian origin of South Needwood Blue (United Kingdom), Fenton Blue (United Kingdom),

American chickens, brought to the western coast of South America Sapphire (United Kingdom), Gruneleger® (Germany). All British before its European conquest. The blue-green egg colouration is hybrids were based on Cream Legbar and have a similar phenotype. due to deposition of pigments biliverdin IX and zinc biliverdin chelate An exception is the hybrid Sapphire, which is with white plumage. during the eggshell formation. The mutation is provoked by an EAV-The German Gruneleger® was created from Araucana and White HP insertion in the SLCO1B3 gene situated in the О locus of the Leghorn breeds, and their phenotype and production traits resemble poultry genome's chromosome I. The genotype and phenotype those of Leghorns. In Japan, egg-laying hybrids producing blue-variety provided by these breeds and breed groups could assist in green eggs have also been created, and the most popular among maintaining the genetic diversity of Gallus gallus domesticus. them probably is the Blue egg layer G7. In the USA, hybrids on the

basis of Araucana and White Leghorn are also under selection (Lukanov et al., 2013). Now in Bulgaria the possibility of receiving the blue egg laying hybrid on the basis of a Rhode Island Red and ReferencesSchijndelaar breeds is explored. Figure 7 presents a 4-month-old pullet from this project. The ban on rearing layer hens in Alders RG and Pym RAE, 2009. Village poultry: still important to conventional cage systems within the EC (Council Directive millions, eight thousand years after domestication. World's Poultry 1999/74/EC) and the consumers' demands in Western Europe for Science Journal, 65, 2, 181-190.

Figure 6. White Schijndelaar rooster (orig.) Figure 7. Schijndelaar/Rhode Island Red cross pullet for production of blue-green eggs (orig.)

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Review

Genetics and Breeding

Nutrition and Physiology

Production Systems

Blue-green coloured eggs in Gallus gallus domesticusH. Lukanov

Investigation on the resistance of doubled haploid sunflower lines to some biotic factorsM. Drumeva, P. Yankov, N. Nenova, P. Shindrova

Usage of cluster analysis for grouping hybrids and evaluation of experimental mutant maize hybridsM. Ilchovska, I. Ivanova

Biological fertility and milk yield in Bulgarian Dairy Synthetic Population sheep according to breeding lineN. Stancheva, I. Dimitrova, S. Georgieva

In vivo digestibility of cereal-based diets supplemented with sunflower vs. rapeseed mealM. Yossifov, L. Kozelov

Histometrical parameters in third eyelid (Harderian) gland of the common pheasant (Phasianus Colchicus Colchicus)D. Dimitrov

Studies on some cherry clonal rootstocks in nurseryG. Dobrevska

Parameters of "yield – irrigation depth" relationship for sunflower grown in the region of Plovdiv A. Matev, R. Petrova

Optimization of thickness of thermal insulation for roofs of turkey's housesR. Georgiev, V. Dimova, K. Peichev, Р. Georgiev

Sulfo technology for multiplication of sunflower hybrids resistant to tribenuron metil-based herbicidesC. Melucă, N. Pîrvu, T. Nistor, R. Sturzu, A. Stoilova

Influence of universal liquid fertilizer MaxGrow on yield and quality of durum wheat (Triticum durum Desf.) cultivar Progress G. Panayotova, A. Stoyanova

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Effect of different types of main soil tillage on the vertical distribution of maize seeds in the soil layer and on the development of the plantsP. Yankov, M. Drumeva

Analysis of energy consumption for artificial lighting of rooms for fattening of pigsV. Katsarov, K. Peychev

Influence of Herbagreen mineral fertilizer on seed production of cucumber, melon and zucchiniN. Velkov, V. Petkova

Soil properties and salt content of soil from Inland salt meadow near Radnevo townM. Todorova, N. Grozeva, D. Dermendgieva

Botanical composition of the main pasture types in Sakar and Strandja regionV. Vateva, K. Stoeva, D. Pavlov

New data for Leucoagaricus and Leucocoprinus (Agaricaceae) in BulgariaM. Lacheva

Development and characteristics of accessions of Eragrostis tef (Zucc.) Trotter in the South DobrudjaH. Stoyanov

Possible adverse effects of tetracyclines on the human health and the environment

Y. Koleva, T. Dimova, G. Angelova

Contemporary assessment of the development of the genus Chaetoceros in the Bulgarian coastal watersD. Petrova, D. Gerdzhikov, G. Kostadinova

Ecological assessment of the phytoplankton community in the Bulgarian Black Sea coastal waters D. Petrova, G. Kostadinova, D. Gerdzhikov

Biopolymer matrix systems for incorporation of biologically active substancesS. Dyankova, A. Solak

Agriculture and Environment

Product Quality and Safety

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thmance in dairy cows,IX International Conference on Production Diseases in Farm Animals, Sept.11 – 14, Berlin, Germany, p. 302 (Abstr.).Thesis:Penkov D, 2008. Estimation of metabolic energy and true digestibility of amino acids of some feeds in experiments with muscus duck (Carina moshata, L). Thesis for DSc. Agrarian University, Plovdiv, 314 pp.

The Editorial Board of the Journal is not responsible for incorrect quotes of reference sources and the relevant violations of copyrights.EthicsStudies performed on experimental animals should be carried out according to internationally recognized guidelines for animal welfare. That should be clearly described in the respective section “Material and methods”.

Volume 6, Number 1March 2014