SauryaKarmacharyaB.Sc.Ag 5thsemesterClass Roll no.135 Exam Roll no.
387Agriculture andForestry [email protected] ABSTRACTThe poultry industry in Nepal is developing ata rapid rate in the present years in both numerical and economical terms.Observing, comparing and contrasting the data from the past with that of thepresent, it is clear that the most important traits of both broilers andlayers, which are also the most economically important, play a vital role notonly in poultry production but also in the genetic improvement of the species.The traits that are of monetary value are generally known as economic traits.Egg size, egg quality, age at maturity of the pullet, rate of lay are the majoreconomic traits of the layers whereas body size and confirmation, meat quality,feed conversion rate, growth rate arethe major traits of economic importance in broilers.
Literature review on thedata of these economic traits shows that average weight of broilers and averagenumbers of eggs laid by layers are increasing at an increasing rate after theshifting from older selection parameter (live weight) to the aforementionedmodern selection parameters of economic traits. Genetic and molecular researchon these economically important traits seems to be one of the most promisingsectors for the future of poultry industry.Key words: economic traits; poultry; broilers; layers;parameters of economic traits INTRODUCTIONPoultry is one of the most important sourcesof income due to the high economic values of meat and eggs.
Poultry productionalso contributes a good share to the national GDP (Recent data shows that thecountry has become self-sufficient in terms of eggs).The poultry industry is a rapidly developingeconomic sector, over 65,000 people are employed in commercial poultry farming.The size of Nepal’s poultry market has grown by 30 percent in the last fiveyears to Rs.20 billion now, and the GDP contribution of the sector stands ataround 4 percent, according to the latest data compiled by poultryentrepreneurs. The size of poultry population has significantly increased inthe recent years and the present population of the laying hens is 7290875(statistical data from MOAC, 2009/2010), the meat production from poultry 17551metric tonnes (MOAC, 2009/2010), the net egg production from laying hens 6,34,60,000(MOAC, 2009/2010). According to the Nepal egg producers’ association, poultryfarming contributes around 4 percent to the GDP of the national economy.
Selection of economically important traits ofpoultry by the breeders and farmers has played a major role in the rapiddevelopment of this sector. Further understanding of such economic traits willhelp maintain this development in poultry sector.Economic traits are thosewhich have monetary value in the livestock and poultry production.Generally, traits are of three categories, Qualitative, quantitative andthreshold traits. Most of the economictraits are governed by many pairs of genes so known as quantitative traitsor polygenic traits. Quantitative traits have more economic importance than thequalitative traits. The variations are observed among the individual fowl when theyare measured from most quantitative traits. If there is no variation amongindividuals, there would be no need to select or cull animals for geneticimprovement.
This is caused by genetic factors (VG), environmentalfactors (VG) and the interactions between genetic and environmentalfactors (VEG). i.e. VP=VG+VE+VEGThe genetic factor may alsobe determined by the interaction among genes and alleles. i.e.
VG=VA+VD+VI where,VA= variance due to additive effect VD= variance due to dominanceeffect VI= variance due tointeractions between genes In the past, live weight ofchicken was considered the most economically important trait. But in thepresent, selection is done on various parameters like feed conversion, eggs,hatchability, weight, breast meat, meat quality, immune response, growthprofile, skeletal integrity, heart/lung fitness, fertility and so on. Thisreview article discusses these economic traits that are considered for theselection of poultry for breeding and commercial purposes. METHODS AND METHODOLOGYPrimary and secondary sourcesof information were gathered by internet based research and internet literaturereview of the past journals, papers and articles. The thematic area of reviewranged from the traits of poultry concerning economic importance, breeding importanceand socio-economic importance.
These specific facts and data were studiedinside the periphery and context of Nepal.The method for the selectionof the traits of economic importance was through thorough review of the pastand present criteria of selection of such traits which is shown below:Past: Live weightPresent: Live weight,hatchability, eggs, heart/lungs diseases, breast meat, meat quality, immuneresponse, feed conversion, lung fitness, skeletal integrityThe review was done underthese parameters each for broilers and for layers. Specific traits for eithertype of chicken was studied which is elaborated under “Results and findings” RESULTS AND FINDINGSThe review findings isdiscussed under the two major headings: Economic traits of layers and Economictraits of broilersEconomic traits of layers The trait egg production ispolygenic in nature. It is a low heritable trait, while egg weight ismoderately heritable and influenced by the environment in which they weregrown. The components of egg production are as follows.1. Age at maturityIt is the age of the bird atwhich it lays the first egg.
Early maturing hens lay more number of eggs, but smallerin size compared to late maturing ones. Modern hen starts laying eggs at 2oweeks. After 72 weeks, the laying hens are culled. Peak period of laying is 5-6weeks after the laying of 1st eggs. Age at sexual maturity isdetermined by both autosomal and sex linked genes. 2.
Rate of layA hen is sexually mature whenshe lays her first egg. The sooner it starts to lay more the number of eggs arelikely to be produced. Probably many genes are involved in its inheritance andsome of these are sex linked.. It is easier to improve the age at the sexualmaturity as it is moderately heritable.
Too early maturity may not be desirablein commercial laying flocks as it affects egg weight. After 1st layingcycle, the laying rate is reduced. 3. PersistencyPersistency refers to theonset of molting at the end of the laying cycle. It is the measure of thelength of lying cycle. This factor is associated with egg production. Thelaying cycle of a hen is terminated by molting. The longer the laying cyclebefore the hen enters her laying cycle before the hen enters her molting period,the better she is for egg production.
The laying cycle should be about 300days. 4. BroodinessBroodiness is the conditionin which females stop lying and show the tendency for nesting. It is an idealcharacter for the propagation of species in wild conditions, but highlyundesirable for domesticated species for economic purpose. Broodiness isdetermined by complementary genes; also it has a sex-linked basis.
5. Egg quality:External quality of the eggis judged from its color, shape, texture and breaking strength (or shellthickness). The internal quality is assessed from the quality of albumen, yolkand the presence or absence of blood and meat spots. Most of the egg-qualitytraits, whether exterior or interior, are highly heritable and respond toselection quickly. White and brown are the most common egg colors.
Hens that lay rough or poorlytextured eggs with thin shells are usually not selected. Breaking strength ismeasured by shell thickness. Thick albumen is preferred to thin albumen, soalso eggs with high proportion of yolk.
Variation is noticed among strains,among families and individuals within a family for blood and meat-spots. 6. Body size:Small or intermediate bodyweight is preferred in layers. Optimum body size is very essential in layingchickens to obtain eggs of satisfactory size. Body weight at all ages is highlyheritable and can be improved by simple mass selection. 7. Feed efficiency:Most of the improvement in feed efficiency has been achievedas a correlated response to selection for high growth rate or egg production.Feed efficiency in layers is measured either as amount of feed consumed inkg/dozen eggs or as amount of feed consumed in kg/kg egg mass.
8. Fertility and hatchabilityFertility and hatchability for a flock are expressed aspercentage in relation to total eggs set. Hatchability can also be expressed inpercentage as a production of fertile eggs set. Breeds, strains, family as wellas individuals within a family differ with respect to fertility andhatchability.
Age of birds, season, nutritional status of flock, diseases andmanagement conditions affect both fertility and hatchability. To improvefertility in a flock the ratio of males to females should be kept optimum. Economic traits of broilers 1. Feed efficiency:Feed efficiency is a ratio of feed consumption to weight gainin broilers. Feed efficiency in broilers has improved considerably in recentyears as a correlated response to high growth rate. Better understanding aboutthe nutritional requirements and formulation of high energy rations have alsocontributed significantly for improving feed efficiency. 2. Growth rateRapid juvenile growth is very essential in meat-type birds.
It helps toreduce the cost of production by saving labor through theapplication of genetic principles and modern methods of feeding and managementit has been possible to develop rapid growing broilers which at 7-8 weeks weighalmost the same as 12 week old broilers weighed about 20 years ago. This hasreduced the marketing age and in most cases they are now sold as early as 6weeks. 3. Body size and confirmationBody size is usuallymeasured by weighing the birds.
Large body weight is very important inbroilers. Conformation refers to body proportions and is more important ifbroilers are not sold as whole birds. Conformation is determined both by bonestructure and fleshing. 4. Ascites resistanceThe rapid growth ofmodern broilers is associated with enhanced appetite and high metabolic rateand, consequently, high O2 demand. The tendency of broilers todevelop Ascites is heritable, but efficacious selection against ASsusceptibility (without affecting the normal expression of other importanttraits) requires identification of indirect selection criteria.5. Heat resistanceTheir higherproduction performance and feed conversion efficiency make today’s chickensmore susceptible to heat stress.
Vitamins and minerals to satisfy the specialneeds during heat stress have been proven advantageous. 6. Eviscerated yieldThe meat-to-boneratio, the skin-to-bone ratio are all considered an economically importanttrait in the broilers. Higher the eviscerated yield, higher the value of thefowl. 7. Skin and meat colorThe importance ofpoultry skin and meat color (both absolute and variations in color) in themarket place has been well established.
It has also been reported that thesecolors change over time. Further review of the economic traits showed that the most economicallyimportant trait in broiler (average weight) and layer (average no. of eggs) areincreasing at an increasing rate, which is shown in the graph below: It showed that the poultryowners are becoming more and more informant about the economic traits of bothbroilers and layers. CONCLUSIONTo conclude, the traits ofeconomic importance are those of the monetary values. The Growth in the averageweight of broilers and average number of eggs by layers from the past to thepresent times indicate that the farmers and the poultry owners are being moreand more informed about the traits with most economic importance such as eggsize, body growth and confirmation, feed efficiency etc.
The increasingcontribution of poultry industry in the national GDP also suggests the same.However, the potential ofdevelopment of such economic traits still remains unexplored as the research atgenetic level and molecular level research are not being conducted at the rateat which they need to be conducted for the full and optimum exploration of thetraits with economic importance. REFERENCES1.
DruyanS, Ben-David A, Cahaner A. Development of ascites-resistant andascites-susceptible broiler lines. Poult Sci. 2007 Jun;86(6), 12832.
LucasJ. Lara, Marcos H. Rostagno. Impact of Heat Stress on Poultry Production. NationalCenter for Biotechnology Information, U.S.
National Library of Medicine3. HayseP, William W. Marion. Eviscerated Yield, Component Parts, and Meat, Skin andBone Ratios in the Chicken Broiler. Poultry Science, Volume 52, Issue 2, 1March 1973, 718–7224.
PetracciM, Fletcher DL. Broiler skin and meat color changes during storage, PoultSci. 2002 Oct;81(10): 1589-975.
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DECUYPERE. Strategies for preventing heat stress in poultry.www.
researchgate.net6. Mishra B, Traits of economicimportance in poultry, bijeshmishra.wordpress.com/2013/01/27/traits-of-economic-importance-in-poultry/#more-16247. Dhakal S, Lamichhane S, etal., Traits of economic importance inpoultry and its implication in genetic improvement programme, https://www.scribd.
com/doc/48643480/Economic-Traits-of-Poultry ACKNOWLEDGEMENTThis review paper on thetopic “Economic traits of Poultry” is prepared as an assignment of course ANB301, Principles and Practices of Animal breeding. The review discusses on theeconomic traits of poultry (broilers and layers) and highlights its importancein the poultry industry of the country and in animal breeding. During reviewingand after the completion of the review paper, most of the things regardingeconomic traits of poultry were understood, of which Asst. prof. NirajanBhattarai, Department of Animal Breeding and Biotechnology is to be thankedimmensely.
I also extend my gratitudetowards my respected seniors Achyut Acharya and Bimochan Paudel of B.VSc. andA.H.
7th semester for guidingme. Last but not the least, I am the most thankful to my batchmates BishalModi, Kanti Thapa and Sushil Sapkota for helping me complete this review paper.Thank you!