This section contains the following sub-sections related to breeds and breeding:
The organic standards and principles
Breed comparisons – table birds
Breeding for improved disease resistance
See also Rearing replacements
The organic standards and principles
EU Regulation 1804/1999 for organic livestock specifically states that in the choice of breeds or strains for organic systems must account must be taken of:
· the capacity of animals to adapt to local conditions,
· their vitality, and
· their resistance to disease.
In addition:
· Breeds or strains of animals should be selected to avoid specific disease or health problems associated with some breeds of strains used in intensive production.
· Preference should be given to indigenous breeds or strains.
Details of some of the specific disease tolerance/resistance characteristics of particular breeds are included in the appropriate disease sub-sections of this compendium. In particular, there is evidence of breed differences in the risk of feather pecking,
The Poultry Club of Great Britain classifies breeds into five categories;
· Hard Feather breeds that have their origins in the development of birds for cockfighting. The modern hard feather breeds (Old English Game Bantam, Old English Game and Modern Game) are primarily kept for the showing.
· The Soft Feather Heavy breeds were developed as table birds;
· The Soft Feather Light breeds were developed for their egg laying abilities.;
· True Bantam breeds are naturally small and have no large counterpart were initially developed for exhibition and ornamental purposes some have been developed as a utility breed.
· Rare breeds.
From McLean, Jones, & Frost, D (undated)
The breeds commonly used in commercial poultry are dominated by those supplied by large international, vertically integrated companies Hoffmann (2005). Hoffman describes the restricted access to pure parent line birds by selling F1 generation birds, and how this process allows the breeding company to remain the sole supplier of useful material. Whilst patents do not yet play a role in poultry breeding, in the future an increasing interest in for disease resistance might change this situation (Hoffmann (2005)).
The ancestor of the modern chicken breeds is the wild jungle fowl Gallus gallus. Moiseyeva et al. (2003) compared four postulated chicken breed lineages, egg-type, game, meat-type and Bantam, to each other and to the basic ancestral species of jungle fowls. The greatest similarity was found between G. gallus and the egg-type breeds of Mediterranean roots and/or true Bantams.
A comprehensive list of poultry breeds is provided at http://www.ithaca.edu/staff/jhenderson/chooks/chooks.html including photographs plus short descriptions of related breeds, classification, origin, physical features, potential production, egg colour, behaviour, brooding, hardiness and maturity characteristics.
Laying breeds that are suitable for free-range conditions, such as ISA Brown, Hyline and the more traditional breeds such as the Light Sussex and Rhode Island Red, are suitable for organic egg systems. Other breeds popular in some organic systems are Black Rocks and Hebden Blacks. A newer breed, Bovan Goldline has a reputation of being docile and a non-feather-pecker.
Sorensen and Kjaer (1999) compared New Hampshire, White Leghorn and ISA-Brown under organic experimental conditions and found the latter had the highest egg yield although cannibalism was several fold higher. As a consequence, they deemed the breed unacceptable under organic condition unless methods are found to control their behaviour. Rizzi et al (2004) compared egg production in two commercial hybrids (Hyline White and Hyline Brown) with two traditional Italian breeds (Ermellinata di Rovigo and Robusta Maculata) under organic conditions and found the hybrids to have superior productivity.
A common practice in conventional egg production is the use of hens for only one laying period in conventional production. Pryce et al., (2004) highlight the potential for using hybrids that are selected for production over several seasons. Using these hybrids may be appropriate for organic laying units, not just because of the high price of new layers but also because it is more in keeping with organic principles.
The breed of table bird suitable for organic systems are limited by the organic standards (Defra, 2006) requiring a minimum slaugther age of 81 days. Although faster growing breeds used in more intensive systems, such as the Ross/Cobb, are used by some organic producers, there is a risk that they may reach an unmarketable weight and may become so heavy that they could suffer musculo-skeletal problems. Although slower growing breeds are best suited to organic systems, there may be problems with availability and cost of these as day old chicks.
Examples of suitable slower growing breeds include: Sasso, Poulet Bronze, Poulet Grey, Sherwood Gold, Hubbard ISA 657, 257 and PAC57.
White-feathered broilers dominate world poultry meat production owing to their rapid growth and high feed efficiency. However, consumers' preference for colour-feathered and slow-growing meat-type quality chickens is growing in certain regions of the world Yang and Jiang (2005) . The 'Label Rouge' breed in France is perhaps the best example (see Production Systems).
Pryce et al (2004) give various reasons why broiler breeds bred for intensive conventional production are not well suited to the very different production conditions specified in organic standards.
· Genotypes that have been bred to suit intensive, indoor management systems focused on rapid growth, increased feed efficiency and increased processing yield.
· The high productivity of these strains depends on high levels of feed, health treatments and other inputs, the absence of which can result in disease and poor welfare.
· Most modern genotypes are bred to suit a specific market destination (e.g. well-fleshed birds processing and smaller birds roasting) within a short period of production, typically over 5-6 weeks and are thus not suited to organic production, which emphasizes a minimum period of 12 weeks to slaughter.
· Modern breeding has focused attention on the production of a single poultry product, either eggs or meat and hence the suitability of many hybrids for dual purpose production has been lost.
· Genetic selection for high productivity in conventional strains of broilers and layers has led to deterioration in animal health (Rauw et al., 1998; see Breeds and Health).
ADAS (2002) drew the following conclusions from Defra-funded project AW0221 regarding breed suitability:
· Breeds should be chosen for use in an extensive production system according to their growth profile when daytime access to feed is not restricted.
· Active and inquisitive breeds should be chosen for use in extensive production systems as they are likely to be better rangers and foragers than the less active broiler hybrids.
· Breeds that show extreme escape responses and ground peck in a stereotypic manner should be avoided as they will be more difficult to manage and there may be a risk of aggressive feather pecking.
· Feather colour may affect the chickens’ ability to hide from predators; white feathering may increase the risk of predation.
Breed comparisons – table birds
Many slow-growing genotypes are available in Europe, and researchers have suggested that although the growth performance of slow-growing birds is less efficient than that of fast-growing birds, slow-growing birds are more adapted to natural systems, and the quality of their meat is more appropriate for a specialty or gourmet market (Fanatico et al, 2005). ADAS (2002) characterised, across a wide range of breeds, suitability for use in extensive production systems (see Defra project AW0221).
Nielsen et al. (2003) compared Ross 208 and Labresse cross broiler strains fattened outdoors from 42 to 84 days under low and moderate energy feeds. The Ross 208 strain was found to have a faster growth rate, poorer litter quality, more dermal lesions and impaired mobility, poorer gait score and pectoral myopathies and were considered unsuitable for 12 week growth in free range production systems. The Labresse crosses were observed to use outdoor areas more frequently and used more of the outside area. However, feather pecking and cannibalism only occurred in Labresse crosses and the suitability for free-range meat-type poultry production of that particular cross-breed is questionable. Interestingly, more birds on the moderate energy feed regime were observed outside.
Ali and Brenoe (2002) compared a commercial broiler breed with the Barred Plymouth Rock and Jaerhon breeds under intensive (ad libitum feeding) and extensive (restricted feeding) systems from 7 to 20 weeks. Whilst the commercial breed performed the best under intensive conditions, under the extensive regime it lost the greatest potential body weight. Interestingly, males expressed their growth capacity much less than females under extensive conditions. It was concluded that both genetic and underlying size differences should be considered in breed comparisons, particularly when chickens are subjected to different feeding regimens.
Fanatico et al. (2005a and 2005b) evaluated slow, medium and fast growing genotypes and showed meat quality, growth performance and yield differences exist among genotypes with different growth rates and reared with or without outdoor access. In the slow growing breed only, the effect of outdoor access was to make the meat more yellow. Slow growing genotype had the highest feed intake and hence the lowest feed efficiency. Birds given outdoor access had greater bone strength in the tibia, and the faster growing genotypes had the highest bone strength. Slow growing birds had the lowest feed efficiency, the lowest breast yield and the greatest leg quarter yield. The slower-growing genotypes showed a good adaptation to the extensive rearing conditions, while the fast-growing genotype showed unbalanced muscle response to the greater activity and the oxidative stability of the meat was reduced.
Ristic (2003) compared slow growing genotypes ISA J457, J257, JA 57, Shaver RedBro and rapid growing genotypes, Sena Double Breast and Ross Mini with Ross 308 under conventional, free-range and organic farming methods and found that alternative production methods did not produce any significant improvement in organoleptic traits compared with conventional production. However, length of fattening period and broiler genotype influenced organoleptic properties in some cases. Ristic et al. (2004) also examined three slow growing hybrids suitable for organic production and recommended the fattening duration of at least 81 days can be shortened by virtue of the genetic potential.
A comparison of three traditional Italian breeds Bianca Saluzzo, Bionda Piemontese and Valdarnese Bianca showed that the breed that the slowest growing breed and the one deemed best suited to organic rearing conditions (Valdarnese Bianca) also had a stronger anti-predator response and was therefore probably also better suited to free-range conditions (Ferrante et al., 2005).
The characteristics of Polish breeds that would be suitable for organic production are described and efforts to conserve these breeds are discussed by Cywa-Benko (2000).
A German trial compared meat production from male brown layers hybrids (Meisterhybrid) with commercial fast growing broilers (Ross PM3) and found the costs and meat quality to be unacceptable (Damme and Ristic, 2003)
ADAS (2002) characterised, across a wide range of breeds, suitability for use in extensive production systems (Defra project AW0221). This took into account the effects of feed specification and diurnally fluctuating post brooding temperatures as would be experienced by outdoor chickens. The results indicate that across the range of breed-types available, domestically or through importation, it is possible to choose breeds on the basis of growth profile and desired market live weight at slaughter age, when feed is not restricted during the daytime. Breed differences were recorded in live weight, feed usage and FCE. There were four breed-types used, viz.fast growing, medium to fast growing, slow growing and very slow growing. Fast growing breeds were broiler hybrids Ross 308, Ross 508, and Ross YA x PM3. Medium to fast growing breeds were the commercial hybrids Hubbard ISA 757, ISA 957, Redbro, and Master Gris. Slow growing breeds were commercial hybrids Hubbard ISA 457, ISA 657, and Gris Barre. Very slow growing breeds were traditional UK breeds Light Sussex, White Sussex, Ixworth and White Dorking (ADAS, 2002).
There were breed and feed effects on mortality to 81 days of age. In fast growing and medium to fast growing breed-types mortality to 81 days of age was greater when fed high specification rations. A high number of fast growing birds were culled due to gait abnormalities post 56 days of age and in medium to fast growing breed-types the high specification rations tended to increase the incidences of ‘flip overs’ and leg culls. Feed specification did not affect mortality to 81 days of age in slow growing breed-types, but in the very slow growing breed-type, more White Sussex birds fed high specification rations died compared with other breed and feed treatment combinations and this was due to aggressive pecking (ADAS, 2002).
The traditional, lighter UK breeds were more active and showed more extreme escape responses when approached by a human than did the heavier breeds. Some of the UK traditional breeds ground pecked in a stereotypic manner. Gait was similar in all breeds when live weight was accounted for in the analysis.
Although some breeds tested positive at day old for Mycoplasma gallisepticum and/or Mycoplasma synoviae, all breeds tested negative at about 35 days of age. None of the samples taken tested positive for Salmonella spp.
“Animals in a population that have been genetically selected for high production efficiency seem to be at more risk for behavioural, physiological and immunological problems” (Rauw et al., 1998).
The increased incidence of heart failure syndrome and leg problems in intensively reared broiler chickens is an example of undesirable correlated responses to selection for body weight at a certain age, using a high selection intensity and a short generation interval common in commercial broiler production (Rauw et al., 1998)
Rauw et al. (1998) classed these negative genetic effects of breeding for high productivity into reproductive difficulties, disease and reduced immune performance and metabolic effects. For more see Pryce et al., 2004).
Breeding for improved disease resistance
There is considerable evidence of genetic variation in susceptibility, tolerance, resistance and immune response to many of the main diseases or conditions that affect poultry. An increase in the level of genetic resistance provides a possible means of enhancing protection of flocks (Bumstead, 1998).
Some health traits, such as ascites, are only partially correlated genetically with high production and therefore it is possible to select animals that not only perform well, but that also have good health. Metabolic disorders are strongly influenced by nutrition and environment but also have a genetic component. (see Pryce et al., 2004 and Thorp and Luiting, 2000).
Large differences in resistance to coccidiosis have been observed between genetic lines (Pinard-Van et al., 1998). Resistance to mortality and resistance to the carriage of S. enteritidis do not necessarily coincide within breed lines. Bolder et al (2002) showed that some lines suffer showed high mortality rates yet low levels of carriage. See conditions listed in Disease List for more on breed resistance to specific diseases.
Conventional breeding (selecting on phenotypic traits) is the easiest strategy for the genetic improvement of disease resistance, and has already been applied to Marek’s disease and Newcastle disease (Friars et al., 1972, and Gordon et al., 1971, respectively).
Pryce et al. (2004) view the inclusion of some traits important for health and welfare alongside more conventional traits in poultry breeding indexes can result in the production of breeding birds that meet the requirements for organic egg or poultry meat market. This combines requirements for high production whilst minimizing the risks of associated health and welfare.
Thorp and Luiting (2000) provide a discussion on the main poultry health problems that may have breeding solutions.
Breeding influences behavioural characteristics such as feather pecking and cannibalism and hence genetic selection can also be used to reduce the effect of these negative characteristics. Feather pecking and cannibalism have heritability estimates that justify consideration in an organic breeding programme (Kjær 1995; Muir, 1996; Kjær and Sørensen, 1997; Kjær et al., 2001). Pryce et al (2004) also view other behavioural characteristics, such as the ability to use roughage and reaction to predators, as being of potential benefit if included within organic breeding programmes.
Selection for production traits may cause side-effects on the physiology and behaviour of the birds with a potential influence on animal welfare (Vaisanen et al., 2005). Comparing crosses of red junglefowl and White Leghorn they concluded that selection for high production may also have side-effects on sociality and foraging which in turn could influence the general capacity of birds to cope with environmental challenges such as exploring a novel environment.
Most selection programmes only include productivity and tend to ignore animal welfare impacts. Breeding for productivity can result in welfare-negative competitive production situations (Muir and Cheng 2004). They show that selection procedures that account for competitive interactions (i.e group selection and advanced models that account for indirect genetic effects (competition)) have resulted in dramatic improvements in liveability, productivity and welfare. Selection for high production may simultaneously have side-effects on sociality and foraging which could influence the general capacity of birds to cope with environmental challenges such as exploring a novel environment (Vaisanen et al., 2005)
Global gene expression profiling and QTL scans should enable the mapping of genetic pathways that control growth, development, and metabolism of chickens. Gene mapping is an emerging technology which will have broad applications for poultry breeding programs (i.e., use of molecular markers) and for future production systems (i.e., the health and welfare,of birds and the quality of poultry products), including progress associated with crossing fast and slow growing lines (Cogburn et al., 2003; Yang and Jiang, 2005; Ellegren, 2005 and Fumiere et al ., 2003).
Indirect selection via genetic markers has great potential and has already been used for control of Marek’s disease (Thorp and Luiting, 2000). Particular research emphasis has focused on typing the MHC (major histo-compatibility complex) genes, which exert major genetic control over host resistance to disease. Although there is potential for transgenesis to become available for the control of avian disease, it is very unlikely that this would be considered acceptable in either conventional or organic farming because of public opinion.