Genetic selection and organic production in poultry farming
To select most suitable birds, different techniques have been used, at different times, depending on the procedural instruments, the mathematical knowledge or the evolution of the genetic science available.
Authors: Jaime Borrell and Eduard Torres
Índice de Contenidos
- 1 Introduction
- 2 Traditional selection system
- 3 Quantitative selection system
- 4 Genetic selection system
- 5 Crossings and selective parameters
- 6 The origins of current poultry breeds
- 7 The conservation and improvement of native breeds
- 8 Molecular genetic selection system
- 9 Future criteria
- 10 Introduction of organic rules in birds breeding
- 11 Conclusions
The current breeds, lineages, poultry lines and hybrids come from wild breeds originating in South and Southeast Asia. Although they initially arrived in the West for various purposes (combat birds, decorative birds or egg producers), European breeders and later scientists saw in these animals an extraordinary potential of meat and egg production to feed a growing human population.
To select most suitable birds, different techniques have been used, at different times, depending on the procedural instruments, the mathematical knowledge or the evolution of the genetic science available.
A first phase based on observation and empirical success-error trials was established.
The second selective phase was based on the quantification of the productive parameters (saving the daughters of the most productive hens) followed by a third phase based on genetic and mathematical knowledge. In recent years, selective concepts related to molecular genetics have been introduced.
These different historical stages are reflected in the current selection programs of the research groups, public or private, so that the majority is based on the crossing of 4 races until reach F4, a commercially exploitable hybrid
In the following sections we describe each step:
- Traditional phenotypic and empirical selection
- Quantitative selection
- Genetic selection
- Criteria of crossings previous phases
- Molecular geneticselection
- Future criteria
Traditional selection system
The traditional selection, based in Asian breeds, was carried out during the nineteenth century based on the fixation of phenotypic characters from one or several breeds. Depending on whether the sons looked the same as the parents, it was considered that we were facing a race and not a hybrid.
The traditional basic genetic selection program uses 4 pure breeds or lineages F0 (pedigree): A, B, C and D, that reproduce with exclusively numerical effects.
Thus, F1 (great-grandmothers) are still 4 pure races A, B, C, and D, that begin to cross.
The most frequently used breeds are:
- For white egglaying birds, we start from 3 or 4 lineages of a single white Leghorn breed, as it is the best laying breed. Sexing is done by observing the cloaca (Japanese style).
- For colored egglaying birds, we start from 3 breeds, Rhode Island Red or New Hampshire if it’s male and Plymouth Rock Barrada if it’s female. The chick obtained is self-sexable by the feather color. (White spot in the forehead due to the effect of the gene related to barred plumage in adult males).
- For poultrymeat production, a White Cornish male (adds weight and precocity) is joined with a female from two lineages of White Rock (which provide better conformation of carcass and breast).
Quantitative selection system
The quantitative selection system is based on “saving” for the next generations the daughters and sons of those most productive parents.
Thus, the F2 (grandmothers) is composed of AB mails, AB females, CD males and CD females.
Basically, it is about saving the daughters and sons of the animals with the greatest laying (egg selection) or of greater weight (meat selection).
We should point out that males can be selected as carriers of characters related to laying or females with characters related to meat production. Likewise, we must bear in mind that in this time Mendel’s principles are already known but the structure of DNA and the existence of genes are unknown.
Genetic selection system
The F3 (parents) is composed of males (M1H1) x (M2H2) and females (M2H2) x (M1H1). That they cross giving rise to the commercial hybrid F4 (M1H1M2H2).
Crossings and selective parameters
The crosses described so far can be done in different ways:
- Birds crosses of different races.
- Crossbreeds of consanguineous lines of the same race from brother x sister crossing.
- Crossbreeds of consanguineous lines of different race.
- Crossings of birds of the same generation.
- Crossings of related birds of different generation.
The number of individuals usually used, is 25 roosters for 250 hens per batch.
These techniques seek by phenotypic and quantitative selection of individuals, the accumulation of favorable genes and the reduction of the presence of unfavorable genes.
F0 and F1 birds are selected by evaluating their phenotypic condition along with their genetic history (pedigree). We will always choose the best individuals from a population.
F2 selection is carried out bearing in mind the heritability of the characters in males and females.
Thus, individuals with the favorable characteristics of greater heritability will be selected.
There are different objectives depending on whether the final production is; reproductive, meat production or egg production.
1.1. Number of eggs per sequence without broodiness.
1.2. Egg weight.
1.6. Weight and age of arrival at maturity.
1.9. Heat adaptation (stress tolerance).
1.10. Bird flu outbreak survivors.
- Meat production
2.1. Daily gain weight, Studies (Guilt 1974) have shown that a better conversion rate in breeders influences on dairy weight gain (GDP) in the next generation.
2.2. Weight at 10, 20, 30 days. Fox studies (1954) show that food consumption in breeders influences the weight of the next generation.
2.3. Food efficiency. Thomas studies (1958) show that the conversion rate between 4 and 10 weeks in breeders influence the conversion rate in the next generation.
2.4. Carcass yield and breast performance.
2.6. Bone density.
2.7. Feather: coverage and speed.
2.8. Heat adaptation (stress tolerance).
2.9. Disease resistance.
- Egg production
3.1.Egg productionmarketable per bird
3.2.Persistence of laying without broodiness
3.4.Conversion eggper kg of egg
3.6.Internal eggquality (Haug units)
3.7.Shell quality (strength and thickness)
3.9.Acceptance laying in nests
This objective must adapt to the changing demands of the poultry industry and consumers. It is considered that genetics should work 5 years in advance.
The mating can be carried out in group breeding or directed in cages by couple or by artificial insemination.
The using selection method is carried out among siblings, through family averages, which will be used for the evaluation of each individual. If the pressure is high, the selection is accelerated, but variability is lost. If the pressure is low, selection speed is lost. The rule of prudence is to select 25% of individuals (never less than 20 or more than 30).
The origins of current poultry breeds
Domestic animals come from wild individuals through the complex process of domestication, on which great questions still arise. Time, playing in favor of the natural selection imposed by the environment and natural genetic changes (crosses, mutations), has been differentiating the species, but the breeders are the consequence of the action of men on the populations of existing domestic animals in his territory.
Genetically different races have developed under the effect of the interaction between man-made selection and adaptation to the environment.
The possibility of genetic characteristics manifestation is conditioned environmental circumstances, whether natural (orography, climate) or artificial (accommodation, food, and management; therefore, under very harsh conditions of feed, health and management, there would have been no productive selection, but adaptive. And so, the native race continued, while the majority were little evolved production systems, demonstrating its superior adaptation to the environment.
Commercial animal husbandry has introduced new elements of confusion by mixing different terms and removing them from their true scope. This is how we speak cheerfully about varieties, lineages, lines, synthetic breeds, hybrids (interracial mestizos or interlinear crossing) etc., without specifying exactly what is considered as such.
Therefore, when talking about birds, it is very common to confuse the terms when referring to a group of animals with specific characteristics. Even in some articles it seems that the author is not clear about what a breed is, when referring to a group of animals with specific characteristics. The concepts are mixed such a way that sometimes it seems that the concept “breed” has no entity on its own.
In this work we consider that a “breed” could be defined as “the subset or population of individuals of the same species that have common and different characteristics from the other populations of that species and whose descendants are practically identical to the parents and resemble each other more than any individual of another breed” (Jordana).
Thus, we accept that a native breed is the consequence of adaptation and selection by man in a territory with certain geographical conditions (orography, climate), in a specific environment (cultural, social and economic development) and under generally harsh conditions of feed, accommodation, health and management, that did not facilitate a productive selection, but adaptive.
Today it is required that, who defines a race (Breeder, Association, Experts), to do so meets a minimum of requirements that ensure the specificity of the characteristics that define a race and its hereditary transmissibility, and that can be synthesized in three points:
- The breedconstitutes a homogenous set of animals of the same species, whose morphological characteristics respond to those of previously established pattern.
- These morphological characteristics, which serve to define the animals of a breedand differentiate them from the rest of the same species, must be easily perceptible.
- The characteristics must be genetic; that is, transmitted by inheritance from generation to generation.
Over time, and following human migrations, races were diversified and distributed through the different territories. Today, there are 67 breeds of hens registered in five countries or more. 26 of them originated in Europe.
Since the mid-twentieth century, a small set of high-yielding breeds has spread throughout the world and has often displaced traditional races. But this “improvement” is not free. When high performance breeds and intensive production systems replace local breeds and local production systems, the constant flow of genes reduces the genetic diversity of the population.
We cannot accuse “globalization” in general, and much less, intensive poultry production of this reduction in genetic diversity, have the causes have been many and diverse:
- The use of exotic germplasm
- Changes in production systems
- Changes in producer preferences due to socioeconomic factors
- Different catastrophes (droughts, famines, epidemics of diseases, civil conflicts and wars)
- Development interventions
- Specialization (attention to a single productive feature)
- Genetic introgression
- Technology and biotechnology development
- Political instability
Summarizing, three broad categories can be distinguished:
- Trends in the livestock sector
- Quantitative and qualitative changes in the demand for livestock products and services
- Changes in the availability of natural resources, external inputs and labor
- Changes affecting nationally and internationally livestock trade
- Changes in the political environment that, directly or indirectly, affect the character of livestock production systems
- The low valorization of local breeds
- Catastrophes and emergency situations
- The epidemics of animal diseases and the measures to combat them.
(Adapted from Rege and Gibson and Tisdell; 2003)
Poultry companies have dedicated a lot of time and effort to achieve the production levels of current lineages, curiously from native breeds, and today these breeds are the main support of the poultry industry.
Today, 19 of 67 main lines of commercial strains dominate the worldwide distribution of hens. As the interested companies keep the secret information of improvement, there is no data on the provenance of theses strains. However, it seems that most derive from White Leghorn, Plymouth Rock, New Hampshire y White Cornish (Campbell y Lasley, 1985).
The Leghorn breed, which appears in the first place as the most widespread breed worldwide was selected in the US from Italian chickens from region of Tuscany, embarked in the port of Livorno, from which it took the name (Livorno, in English is Leghorn) in the year 1835 bound for the US. And crossed with other races, possibly of Spanish origin, all chosen for their high laying. Today, most white-shell eggs depend on leghorn hens, although industrial laying hens come from the crossing of several specifically selected lines.
Most of the commercialized broilers today are the result of a cross between a white Indian Fighter cock (also called white Cornish) and a white Plymouth Rock hen.
The Plymouth Rock breed (the quintessence of an American breed), comes from a cross of Dominica and Black Java (and other Asians such as Cochinchina and Brahma), which was developed in the mid-nineteenth century (1960). The Rhode Island Red breed, classic type (the American icon hen) was originated around 1845 in the state of Rhode Island, crossing the native hens with Malay Combatant and Cochinchina.
And the use of native breeds in commercial strains continues. Lately, the rise of the farms of “breeding in freedom” or “free-range hens” has made these companies fix their attention to this market, offering special lineages or lines.
Currently most of the breeds used in free-range or ecologic poultry farming are industrial hybrid breeds resulting from the crossing with the Rhode Island Red breed. Although, due to its rusticity and heat resistance, the naked neck” lineage have become popular based on the introduction or the “NA” gene through crossbreeding with the French “Frozen naked neck” breed or with other populations with the same character, descendants of those discovered in 1873 in Transylvania by surgeon J. Clush.
Altogether, today, big genetics companies offer a full range of possibilities, for which they keep jealously protected their farms of purebred cattle and are the first interested in maintaining the genetic variability of birds to be able to create, by means of adequate crossings, new lines that can adapt to new market situations.
The native breeds still have great values, and not only because of their role in the creation of new commercial strains or what they represent as a living memory of our history culture.
- The native breeds belong, in general, to genetictrunks far removed from the industrial breeds and, therefore, are the responsibility of a genetic diversity that is worth keeping.
- Even in the strictly productive area, improved breeds, with high productions, also require excellent handling and feeding conditions to demonstrate their qualities and, in not-so-favorable environments, or do not perform economically because they condition prohibitive costs, or are incapable to prosper.
- Many of the native breeds are vital for foodsecurity and the livelihoods of the populations that maintain them. They are more resistant and less likely to be prey to disease and are low risk proposal for pastors.
- The native breeds are populations well adapted to specific means. It is possible that in better conditions they will not produce as much as their high-performance relatives, but in the extreme environmental conditions in which they developed they can produce under conditions in which other races do not survive.
- They are also an integral part of their environment contributing to maintaining biodiversity. Many of them, play a central role in the cultures of the population who raise them.
- A lot of them have unique characteristics, and a specific geneticvalue such as, major genes of economic importance, superiority in some productive character, level of resistance superior to certain diseases or tolerance to extreme climates, and represent an important source of genetic diversity that can be used against to outbreaks of pests and diseases and climate change.
- They are also usually populations with Good prospects of heterosis and complementarity for possible crossing with other races.
- Last but not least, it is important to highlight the qualify on many of the products that can be obtained from their exploitation, which present differential values that may allow them to obtain a higher price in the market that makes their economic exploitation possible.
The conservation and improvement of native breeds
It is clear that the perspectives of a breed depend largely on its present and future role in livestock systems. As circumstances change, some races are marginalized and face de danger of extinction unless action is taken. Therefore, preservation actions are not accompanied by an economic return for the farmer have their problem and their cost, which has to be assumed by someone. And we don’t mean only to the economic cost.
It is not about the conservation or selection of the (foundational nucleus) of commercial lines, but about promoting a conversation and improvement action on poultry farms. From the technical point of view, the most suitable system for the conversation of the animal genetic heritage is the maintenance of animals in their natural environment, in the hands of the farmers that have been exploiting them and that have shaped their current type. However, this generates some socio-economic problems due to the scarce possibilities of probability of some races and their degree of risk of disappearance, which advise not to leave the preservation of breed exclusively in the hands of farmers.
The need to convince the intervening parties (farmers, society and rulers) of the usefulness of making an expense for which there is no immediate benefit. Even more if there is the possibility of performing an improvement action with other breeds or more productive crosses. Therefore, obtaining and managing possible economic support is complex, and administrative and financial mechanisms are not always adapted to the characteristics of these actions.
When we act on a certain number of farms, selection programs can increase the frequency of desirable genes for the productivity and profitability of local breeds significantly. These programs undoubtedly be essential if you want your results to facilitate a viable option for the economy of the participating farmers. Selection programs should take into account the maintenance of genetic variation within the breed, as well as the risks associated with a high level of consanguinity and, for these and other reasons, it is essential to have the close help of a University Department of Poultry Genetics.
With his participation, a detailed study should be carried out to characterize the breed and farms in which it is currently. It must be pretended, in addition to establishing the morphological characteristics and their food and ethological requirements, determine their population structure, their morphological and genetic homogeneity the existence, or not of a race or racial grouping on which one can act and, above all, its chances of survival over time in the current conditions of exploitation. Based in this study, it is necessary to decide which or which of the possible actions are feasible and want to be carried out, depending on the possibilities (mainly economic).
As it has been reiterated, a basic point to improve the economic perspectives of the breed is the improvement of livestock productivity, without losing the characteristics of rusticity, adaptability and others that are their own. Therefore, together with the mere appreciation of morphological characters, which will provide us with a uniform population, attention should be paid to those that are linked to desirable productive or physiological characteristics.
The actions of genetic improvement require a minimum number of animals to achieve appreciable advances in the population, without the presentation of negative factors. Therefore, the first action will be to obtain a sufficient number of animals, coming from different farms, to preserve the population of the consanguineal depression and maintain an inbreeding level of less than 0,2% per year.
To avoid consanguinity, this number should not be les tan 72 birds of each sex. With de exception that, in front of a group as uneven as the “Creole chicken” it is necessary to characterize and value a very high number of birds to achieve a minimum of individuals with the necessary racial uniformity.
If what is intended is to apply, in addition, an improvement program, at least 300 controlled hens per improvement line and per generation will be needed. If what is intended is to provide birds for restocking to the producers, the number of breeders must be increased accordingly, or collaboration agreements with the same producers must be established.
Over the last century, a series of “breeders associations” were created in many countries that carried out various actions to promote and improve the breeds they maintained on their farms, as they had previously done in England, Netherlands and Belgium.
However, the use made in practice of the “genetic improvement” of native breeds is far, sometimes, from what geneticists or the poultry industry understand, among other things because the selection and improvement of breeds Poultry does not always seek, as a basic objective, a productive improvement.
In the “Ornamental Poultry Farming”, breeders’ associations organize various beauty contests that value animals according to canons totally dissociated from productivity, and even positively value characteristics linked to genes with negative effects on animal production or life, but listed in the “pattern” as defining the breed in question.
The “pattern” is nothing more than a description of the REAL bird, which can be seen, but whose characteristics are transmissible and, therefore, appear in their offspring. In ALL his offspring. All breed selection and improvement actions must preserve both the genetic base and the “pattern” that defines the breed. They should not imply, in any case, endanger the survival of the race, nor should it convert exploitation into a “zoological garden” or an “ethnological museum”. Otherwise, it would be obtaining “another poultry population”, different from the initial breed.
In zootechnics, the contests are morphological-productive. An animal is more “beautiful” if its morphology and historical data predict good productive and economic performance. Beauty is functional and “individual’s own” although its predictable in their descendants.
In livestock production, the really “beautiful” is that which is “useful”, not simply the “beautiful” and less the “extravagant”, although it responds to a function of genetic preservation and has an economic purpose. Both purposes can coexist and share facilities, but their PATTERNS, their IMPROVEMENT PROGRAMS, their SELECTION PROCESSES and their OBJECTIVES must be different and not confused. Never forget that it is about getting a COLLECTIVE IMPROVEMENT, not an individual benefit.
Both productive and ornamental breeding have contributed and contribute to the diffusion and preservation of the breeds and may have an economic benefit, but the purpose is different and, usually, incompatible.
As an example of a Good preservation work, to avoid the disappearance of valuable breeds with unique genetic endowments, the Spanish Government has been carrying out various actions to preserve local breeds, both birds and mammals since the middle of the century in the so-called “Livestock Stations”. These were programs of a regional nature and lack of coordination at the state level until 1975, when in the Poultry Farm La Encin belonging to the Department of Animal Genetic Improvement of INIA, began the current Conservation Program of Spanish Breeds, in accordance with the need to maintain the genetic diversity of domestic species (www.inia.es).
In Catalonia the conservation of native hens’ breeds began in 1976, through the collaboration of the various administrations (Autonomous, State and Municipal) with livestock associations, so it already has a history of more than 40 years if we refer to the Prat breed and 33 if we refer to the breeds from Penedès and Empordà.
Since 1993 a production scheme has been offered in Prat Leonada hen, Black hen from Penedès and Red hen from Empordà, from which one chicken of each breed is obtained that has reduced the breeding time by seven weeks to obtain 2,1kg of live weight, has increased the volume meat, is still very suitable for breeding in the wild, the meat retains good organoleptic characteristics and the breeder from which it comes has increased by 35% the number of chicks produced per year of egg lying. The products obtained are endowed with designation of origin.
As proof of the economic return that can be achieved, apart from marginal productions, at this time we can talk about the existence of four brands in the Catalan market, three of which are with designation of origin: Chicken and Capon of the Prat breed, “Penedès cock” and “Empordà chicken”. They are productions as of the improved final products to which we have referred, reproduced and raised by groups of the areas of the origin of the breeds. The fourth, “Gall Sendra de Pota Negra”, is a registered trade name that has been given to a company that breeds the Black hen from Penedès breed in the Baix Camp (which does not belong to the Penedès region) and therefore you cannot use the designation of origin.
With regard to actions at the State level, conservation programs are priority objectives together with genetic improvement programs, balancing a response to the appropriate selection with a minimum effective size to avoid the loss of genetic variability.
Initially, closed lineages of the different Spanish breeds of hens that were disappearing were created due to the replacement by the more productive commercial hybrids.
Simultaneously, the conservation program was given a dynamic character, as a consequence of the increasing importance of production of alternative quality to the industrial one, which meant a recovery of native breeds well adapted to over littered or outdoor production systems.
The conserved breeds are from five different groups:
- Traditional production hens productivas tradicionales (Castellana Negra, Andaluza Negra Barrada, Andaluza Perdiz, Prat Leonada, Prat Blanca).
- Ornamental hens with defined international pattern (Andaluza Azul, Menorquina Negra, Española Negra Cara Blanca).
- New produtive hens (Vasca Roja Barrada, Villafranquina Roja).
- Hens used in the manufacture of artificial fly for fishing (Leonesa Parda, Leonesa India).
- synthetic (Castellana Codorniz), obtained from the cross between the Castellana Negra and Prat Leonada.
There is also a synthetic population of White Leghorn created with three different lineages, as a control in genetic studies, and a recessive brunette line very useful in genetic characterization studies.
Maintenance is done in genealogical chicken coops (in which paternal and maternal genealogy can be controlled) and non-genealogical, with balanced mating (one female of each male chosen at random contributes to the offspring with one male, another randomly chosen contributes with two females, and the rest contribute with one female each) or with cyclic changes of roosters, varying the effective size between 100 and 300 for the different breeds. All chicken coops have trap nests and use a ratio of 1 rooster for every 5 hens.
Genetic studies are of four different types:
- geneticsexing of day-old chicks (unresolved in white egg laying birds anb white plumage meat birds).
- internal and external eggquality.
- molecular markers.
In the first Group, INA has developed three crosses based on the barred, silver, and dermal melanin gene. In the second group, a population with low cholesterol content in the egg, and others with high shell hardness or very dark color without high incidence of internal spots on the yolk was formed. In the third group, three indicators are being evaluated: muscle immobility, leukocyte ratio, and fluctuating asymmetry of bilateral morphological characters. Finally, in the fourth group the genetic distances between the Spanish breeds and other populations have been calculated, and markers related to egg quality and resistance to stress are being located.
The conservation program has provided newborn chicks to numerous poultry farmers.
The Works of conservation and genetic improvement oh hens of IRTA (Institute of Agricultural Research and Technology, Reus, Tarragona), through a specific program began in Catalonia in 1976, with Prat breed. In 1982, in the current Unit of poultry Genetics of the IRTA, the recovery of the other two racial groups began: the hen from Penedès and the hen from Empordà. So, the program already has a history of more than 40 years if we refer to the Prat breed and 33 if we refer to hen from Penedès and hen from Empordà.
In 1984 a population of the Prat breed from the Association of Breeders of Prat de Llobregat was incorpored to the Poultry Genetic Unit. In this way, a program of conservation, definition, characterization and genetic improvement of Catalan chicken breeds was born.This story authorizes us to take the actions carried out by the “Mas Bové” from IRTA as a guide to the procedures to be followed for the selection, improvement and distribution of specimens of a native bird breed. And is fair to pay tribute to the person of Mr. Amadeo Francesch Vidal, recently deceased, promoter, maintainer and “alma mater” of these programs.
Poultry populations, at the beginning of the program, were not on equal terms. While Prat entered the program in a state of very acceptable morphological uniformity, it was not so for hen from Penedès and hen from Empordà that they simply constituted racial groupings, which bore the basic characteristics referred to in the literature and in the popular voice.
It seemed that the best way to proceed was to divide populations into uniform varieties looking for homozygosis of some basic color genes. The first works were based on genetic study of the color in the populations of Penedès hen and Empordà hen in search of these genes and subsequently obtain their homozygosis.
Likewise, the standards that force the selection of this morphological uniformity were elaborated, and which, presented by Francesch, have been recognized even in the Entente European of Poultry.
Once the study and obtaining in homozygosis of color genes to achieve uniform varieties for recognition as a breed was concluded, it was considered that a conservation guarantee for these breeds could be their use for alternative productive purposes, since there was a certain growing demand of what has been called differentiated chickens preceding from a traditional and artisan breeding. This corresponded to the demand of some chickens in which rusticity for the breeding in freedom and slow growth coincided, which increased the quality of their organoleptic characteristics.
The demands of the producers to have some lines that offered better characteristics in the conformation of the carcass yield led the IRTA to gradually modify its improvement program. As indicated, the main objectives of improvement have two purposes: Meat production and egg production, and increase the number of chicks per brood and year of laying, as well as the speed of growth and conformation of the carcass yield.
The production scheme that has been offered since 1993 in Prat Leonada Black hen from Penedès and Red hen from Empordà allows to obtain, from each breed, a chicken that:
- has reduced the breeding time by seven weeks to obtain 2,1 kg of live weight.
- has increased the volume of meat, remains very suitable for breeding in freedom.
- meatretains Good organoleptic characteristics.
- the breeder from which it came has increased by 35% the number of chicks produced per laying year (A. Francesch, Zootec. 47: 141-148.1998).
- the products obtained have obtained the designation of origin, according to EU standards.
La evolución del programa y los resultados obtenidos se exponen a continuación en una revisión actualizada del programa y sus resultados, según el trabajo realizado por A. Francesch, siguiendo las pautas marcadas por la organización de la IX Reunión Nacional de Mejora Genética Animal. (Mejora genética de razas de gallinas catalanas, A. Francesch, IRTA. Centre de Mas Bové. Unitat de Genètica Avícola – Apartat 415 – 43280 REUS).
In 1993, using the data collected up to that time and using REML, an estimate of variance components (Francesch et al., 1997 b) and the response to the selection (Francesch y Iglesias, 1995) was made. This laid groundwork to continue in a multi-character selection using BLUP methodology. The characters that have been considered from that moment have been the number of eggs at 39 weeks of age, the weight and shell color of the egg at 25 weeks and the live weight at 11 weeks. For the number of eggs has been sought the rising, for the live weight, egg weight, and for the shell (hen from Penedès and hen from Empordà), the absence of decrease.
It is observed that the final products of the Penedès hen and Empordà hen breeds have shortened the breeding time by 6,5 weeks to achieve the minimum slaughter live weight, which would be around 2,1 kg. Specifically, they have gone from 18 to 11,5 weeks of life. In the Prat breed the reduction has been 6 weeks, having passed from 20 to 14. All this is accompanied by a reduction in 2,4 points of the conservation index, standing at 3,1 in the hen from Penedès and hen from Empordà breeds and 3,8 in the Prat. According to the characteristics of the carcass yield, the final products have a better conformation that manifests itself in a greater angle of breast and better performance in pectoral muscles. On the other hand, it is not observed that the genetic improvement has had an impact on increasing its fattening, nor on variations in the pH of the meat, nor on cooking losses.
Results in the improvement of the breeds of Black hen from Penedès, Prat Leonada and Red hen from Empordà since 1986 to 1998, in variations of the number of chicks produced by hen and year of laying, weight at 14 weeks of life and conversion rate to achieve 2,1kg of live weight.
Chicks x hen x year of laying
Black hen from Penedès 114-155
Prat Leonada 102-134
Red hen from Empordà 118-163
Live weight (kg) of chickens at 14 weeks of age
Black hen from Penedès 1,6-2,2
Prat Leonada 1,5-2,0
Red hen from Empordà 1,6-2,3
Conversion rate of chickens to achieve 2,1kg of live weight
Black hen from Penedès 4,3-3,0
Prat Leonada 4,9-3,5
Red hen from Empordà 4,5-2,9
Regarding the organoleptic characteristics of the meat, it is also not observed that the genetic improvement has resulted in a modification of the attributes of smell, flavor and texture that have been considered. Only the fact of being able to sacrifice the younger improved chickens is what makes finding a small difference, but significant, in obtaining a greater tenderness, less fibrosity and some variations in flavor attributes, which on the other hand suggests that it contributes to improving the products.
In the maternal lineages, the main character, which is the laying, has manifested an interesting response in all breeds, but at this time higher in the Prat breed than in the other two, which is accompanied by a significantly higher genetic tendency in this breed and inferior in the hen from Empordà, leaving the hen from Penedès located in an intermediate level differentiating itself from the other two, although with an answer, at the present moment, very close to the Prat breed.
Average productive characteristics of the improved breeders of Red hen from Empordà (ER), Black hen from Penedès (PN) and Prat Leonada (PL).
Weights and average biweekly conversion rates of 2 to 20 weeks of life of improved chickens of the breeds, Red hen from Empordà (ER), Black hen from Penedès and Prat Leonada (PL).
Status of conservation and improvement of genetic material
The conservation of these breeds, at the moment, is based on an interrelation between three factors that are: a genetic heritage; a traditional, handmade and quality production; and some breeder associations.
The existence of the element allows that of the other. The conservation of genetic heritage allows the conservation of a traditional production and vice versa. Both elements allow the existence of breeders who on the one hand contribute to the maintenance of genetic resources and on the other a traditional production.
IRTA conserves and disseminates genetic material while advising breeders. It is necessary to separate this activity into two sections:
- Conservation and dissemination of unimproved populations.
- Genetic improvement and its diffusion.
Conservation and dissemination of unimproved populations
It is clear that only a few populations of Black hen from Penedès, Prat Leonada and Red hen from Empordà entered the genetic improvement program, and that, in addition, as we have seen, each breed consists of other varieties that have not been subject to improvement. Specifically, 6 in the hen from Empordà (white, red, blonde and 3 white-blonde), 4 in the hen from Penedès (Black, partridge color, brunette and barred-golden or cuckoo) and 2 in the Prat (Leonada and white). Of these varieties, IRTA maintains a population of hundred hens and 25-30 roosters.
A biannual replacement of the populations with free mating is carried out, considering that the problems that may appear as a result of inbreeding can be solved either by resorting to external breeders or, in extreme cases, to the crossing of populations of the different varieties and then return to the purity.
As an additional precaution, a remnant of fertile eggs is preserved for fifteen days, that is, there is a constant stock of eggs in preservation where the oldest are 15 days old and those of the day replace the group that has turned 16 days old. In this way, an emergency incubation can carry out if there is a problem in the conservation populations.
Fertile eggs and day-old chicks are supplied to interested breeders. In this way, external populations are constituted.
Genetic improvement and its diffusion
On the other hand, populations that are already giving improved final product are still selected. 350 hens are controlled per generation of each of three maternal lines of Black hen from Penedès, Prat Leonada and Red hen from Empordà to which a selection coefficient of approximately 35% applies. Its genetic evaluation is carried out using the BLUP methodology and laying characters at 39 weeks of life and egg weight at 25 weeks are considered. Possible variations of other characters such as live weight at 11 weeks of life, hatchability and eggshell color are also controlled.
The selection coefficient, of the order of 7%, is much more intense in rosters. Once the pairings have been made preventing the crossing up to the level of half-brothers, the BLUP genetic value of each of the future families is predicted, only the roosters of the better 50% are raised, to which an individual selection by live weight is applied at 11 weeks of life and the best two of each family are left.
The paternal lines are also selected. About 700 animals of each breed are controlled per generation. The selection coefficients are similar to those of the maternal and in this case the characters to which selection is applied, and that here can be measured in both sexes, are the live weight at 11 weeks of life and the breast angle at the same age.
The reproduction for the obtaining of the final product crossing roosters of the paternal lines with hens of the maternal ones is practiced by breeders outside the IRTA. In this way, what is genetic improvement is separated from what is obtention from the final product.
Coming from the elite of the population, males from father lines and females from mother lines are supplied to external entities through a collaboration agreement that includes advice. These breeding centers produce broiler chicks, sometimes for themselves, sometimes to be supplied to other breeders.
Apart from marginal productions, at the moment we can talk about the existence of four brands in the market, three of which are with designation of origin: Chicken and Capon of the Prat breed, Penedès Rooster and hen from Empordà. They are productions from improved final products to which we have referred, reproduced and raised by groups of the areas of origin of the breeds. The fourth, Sendra rooster of black paw, has been given to the Black hen from Penedès breed, a company that breeds in a different region (the Baix Camp region) and therefore cannot use the designation of origin.
(Amadeo Francesch, IRTA. Mas Bové Center. Unit of Poultry Genetics) Work presented at the IX National Meeting of Animal Genetic Improvement, 1998 and zootechnical archive vol. 47, no. 178-179
Molecular genetic selection system
The genome of the hen has been studied starting from the Asian Red Jungle Fowl breed. This is the original hen species from which domestic hens descend and has 39 pairs of chromosomes. The current genetic improvement begins in 2004 and incorporates concepts of molecular genetics based on the knowledge of the 39 pairs of chromosomes. Of these, 11 pairs contain the majority of the genetic material (macrochromosomes) and of which the first 5 contain the genes or locci of greater selective interest. The selection is made with the help of computers, which work on the transmission of Single Nucleotics Polymorphism (SNP) markers, giving the process faster. This constant evolution has managed to produce more meat in less time, in the same physical space, with less waste elimination per kg of meat produced due to improved food efficiency and increased growth rate. Consequently, the environmental impact has been reduced (20-25% greenhouse gases).
About 50 locci in meat production and 20 locci in egg production have been identified. Let’s look at some examples of this selection:
- The dwarfism gene (DW) produces a 25% reduction in body weight in breeding females. If it intersects with a normal male DW the offspring will be normal. The advantage is that breeding female consumes less feed, reducing the production costs of the broilerson.
- The NA gene of chromosome 3 related to the bare neck for broilerbreeding in warm weather. It is associated with longer chins and less subcutaneous fat. It is used in birds raised in the tropics. Improves the duration of the laying series and its lengthening. Sometimes it has been used in combination with the “de” gene that seems to enhance its effect on production and relative increase in egg weight concerning to body weight.
- The gene related to docility to reduce cannibalismin laying birds.
- The gene related to intestinal well-being.
- The self-sexing gene is called the S (silver) gene in laying birds. It is linked to sex (the female has a V or X chromosome), it is recessive. If the male has a Z it is normal. If it has 2 Z it is not silver, it is yellowish.
Se considera que la introducción de un gen en una población tiene repercusión 1.4 generaciones del número de individuos de dicha población. Esto supondría una repercusión infinita pero la práctica señala un límite práctico de 70 generaciones.
There is also a limit when the selected value has a negative effect on other values as occurs between:
- Growth, laying and immunity.
- Breast development and mechanical locomotor disorders (tibial dyschondroplasia and bone deformations) by changing the bird’s center of gravity and relative cardiovascular insufficiency that hinders the diffusion of oxygen and nutrients causing deep muscular myopathy.
- Increase in bone calciummetabolism that cause osteoporosis in layers lines and breeders.
- The 24 hours circadian rhythm influences negatively layers with a 26 hours ovulation cycle.
It is considered that poultry farming in park, will need to study the improvement in characters not considered so far as:
- Shape and size of the peak in layers to reduce “social” cannibalism.
- Organoleptic preferences of eggand meat in consumers of non-cage and organic.
- Conservation and introduction of genes of naturally resistant birds (unvaccinated survivors) to especially viral (influenza and infectious bronchitis) and bacterial (salmonellosis) diseases.
- Recovery of chicken lineage “slow” growth (e.g. 2.5kg in 60 days).
Introduction of organic rules in birds breeding
ECOLOGY is, possibly, one of the most commonly used terms and, often, incorrectly in relation to its significance.
According to the dictionary, “Ecology” is the part of biology that studies the relationships of living beings in a given area, with each other and with the environment in which they live.
And “Organic” is everything that is not harmful to the environment. Or, all those who defend and protect the environment.
Well, natural agriculture, indigenous agriculture, family agriculture, peasant agriculture, are types of natural agriculture that seek balance with the ecosystem, are sustainable agricultural systems, which have been maintained over time in different regions of the world seeking to meet the demand for natural and nutritious food for people and animals, so that the agricultural ecosystem maintains the balance.
The native poultry breeds are perfectly integrated in the environment, feed on natural products and proximity, and require less medication because their resistance to diseases is greater.
Is there anyone who says that this is not ecology?
The emergence of a so-called “social environmentalism” has introduced into organic production some factors that have nothing to do with the quality of the product or the production process. These types of movements understand that environmental problems have their origin in an increasingly globalized model of production and consumption, from which other social problems also drive, and that must be transformed, if the ecological crisis is to be avoided.
This form of production, in addition to contemplating the ecological aspect, includes in its philosophy the improvement of the living conditions of its practitioners, in such a way that its objective is attached to achieving the integral sustainability of the agricultural production system; that is, to establish itself as a social ecological and economically sustainable agrosystem.
The native breeds are part of a social, organic and economically sustainable agrosystem and, in addition, contribute to the empowerment of local farmers and improve their diet.
Is there anyone who says that this is not ecology?
To request help for their “SOCIAL” purpose, various entities carry out awareness campaigns, public or legal complaints against those actions that harm the environment, while elaborating concrete and, according to them, viable alternatives, in each of the areas in which those who carry out their activity. The confusion between environmentalism, anti-capitalism, social movements and anti-system that often accompanies these campaigns makes the discussion of these positions remain out of this issue.
In other cases, self-qualifying as “environmentalist” or “ecological” is not enough. You can be an environmentalist, produce organically and not be able to market organic products. Because, to market using the label of “Organic Production” is required to be approved and registered as such.
- Comply with THE REGULATION (Includes the use of organic supplies).
- Spend an adaptation period.
- Overcome periodic external controls.
- Use a specific logo on the label.
According to this Regulation, “organic or biological agriculture (or Poultry Production) is a production system of an autonomous agricultural exploitation, based on the optimal use of natural resources, without using synthetic chemicals or genetically modifies organisms (GMO); neither for fertilizer, nor to fight pests or for cultivation. Achieving organic food in this way, while maintaining the fertility of the land and respecting the environment. All this is a sustainable, balanced and economically maintainable way”.
Is this the only organic?
Organic production is also known, according to the countries, as “ecological”, “biological”, “natural” and other names. This happens because the literal translation of English would not make sense.
“Organic” does not mean “rudimentary” and even “deficient”, but the opposite, since the prohibition of the use of certain substances requires a greater effort in the control and prevention of diseases. In organic production some risks can be minimized (such as the presence of antibiotic residues) but others are increased (such as the spread of diseases and parasitism).
It must be borne in mind that there should be no differentiation as regards the health, safety and quality of the food produced since the regulations require the same requirements and levels in any production system. What differentiates some products from other is that, the production system.
Having said this, any poultry producer, however small, should try to make their production systems as environmentally friendly and “ecological” as possible (in a board sense), and administrations should thus simulate it. But, the decision to market the products covered by this logo must be taken after a thorough technical, economic and commercial study. In this study, we must compare the costs of belonging an associative entity and have periodic inspections and with the additional benefits that commercialize a certified product can offer.
Are organic foods healthier, safer and better for health?
No, “today, there is no indisputable scientific evidence that demonstrates that organic foods -also called bio- are better for health than conventional ones”. At least, that is what a new evaluation of Nutrimedia shows, the UPF Scientific Communication Observatory project –in collaboration with the Ibero-American Cochrane Center and the support of the Spanish Foundation for Science and Technology (FECYT)-, which scientifically analyzes the degree of certainty of messages and beliefs about food and health.
“While the beneficial effect of eating fruits and vegetables is well documented scientifically, for now it is not possible to know if the organic version of these products provides additional benefits for the body”.
And they justify their conclusion that, on one hand, there are little researches that has studied the effects of organic products on health and, on the other, that the degree of certainty of the results of the research available thereon is very low. The available studies are observational and also have important methodological limitations, which reduces the confidence in their results. “Nutrient differences are generally small and probably not relevant for populations that follow a correct diet”.
The current selection programs incorporate all the phases that the poultry industry has historically followed to get prom the Asian wild races to hybrids currently being exploited on the farms.
- Poultry selection is based on 4 techniques: phenotypic, quantitative, genetic and molecular.
- The phenotypic selection allowed to create native breeds from wild breeds imported from South and Southeast Asia to Europe and North America.
- The quantitative selection has allowed to improve the productive qualities of the European and North American breeds through crosses producing hybrids of maximum productivity.
- Genetic selection allowed the introduction of selective criteria based on the heritability of the characters and the relationship between apparently unrelated characters, as well as the use of computers.
- The selection by molecular genetics has allowed to select, in hybrids, specific genes that exaggerate the anatomical development of breast or calcium metabolism to the point of reaching the limit of pathological situations.
- The need to go to organic breeding in the coming years to reduce pollution and feed 10.000 million people Will force us to create a new modality that could call organic genetic. It will include anatomical modifications of the beak, organoleptic composition of meat and eggs, reduction of waste and emissions and resistance to diseases.
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