Development of pure lines with higher immune competence, faster growth rate and lesser physiological disorders is the need of today’s stock. Though evaluation of these traits is expensive and time-consuming, molecular markers are playing important role. Attempts to identify candidate genes related to meat flavour, muscle fibre, lipid metabolism and other physical characters have brought great potentials for future breeding of quality chickens. A number of resources and approaches are now well established, including markers and maps (both genetic and physical), QTL mapping, comparative mapping, EST and BAC resources. Organic egg and meat production has increased continuously over the last decade and will be in the lime light in poultry market in near future.

Environment plays an important role in poultry yield. This could be the housing provided, the climate around to which the bird is subjected like temperature and humidity, quality of feed, the microbial challenge or the compound effect of these factors. A set of environmental factors can be defined and provided to realize the optimum genetic potential of the birds. Construction of closed houses with environment control equipment can maintain optimum conditions. Commercial stocks are obtained by three or four way crosses from their grandparent and parent lines.

Overview of the industry and their effect on society:

Livestock production is growing faster than any other agricultural sub-sector with the prediction that by 2020 livestock will account for more than half of total global agricultural output in financial terms. Demand for, and production of, livestock and livestock products in less developed countries is expected to double over the next 20 years (Delgado et al., 1999). This process has been termed ‘livestock revolution’. This revolution has resulted in industrialisation of livestock production which now changed from being the traditional local multi-purpose activity to an increasingly market-oriented and vertically-integrated business (Delgado et al., 1999). In India the value of livestock output grew by 6 percent per annum in real terms between 1985 and 1992 (World Bank, 1999) where dairy and poultry industries contributed the major share of this growth. In India, poultry is one of the fastest growing segments of agricultural sector which is marked by an increase in the size of the poultry farm. Earlier broiler farms used to produce a few hundred birds (200-500 chicks) per cycle on average whereas now units with less than 5,000 birds are becoming rare, and units with 5,000 to 50,000 birds per week cycle are now common. The production of agricultural crops has been rising at a rate of 1.5-2 % per annum while that of eggs and broilers has been rising at a rate of 8-10 % per annum (Mehta et al., 2003).

Family poultry, which is based almost entirely on native birds, has been by-passed by the poultry revolution and appears to be a stagnant low-productivity sub-sector. The percentage of native birds in the total poultry population has dropped from 50% about 30 years ago to about 10% now (Rangnekar and Rangnekar, 1999). Currently, more than 85 percent of total egg production and 60 percent of broiler production are from improved poultry birds in the organized sector (Mohanty and Rajendran, 2003). Poultry meat and eggs are currently one of the cheapest available sources of animal protein for urban Indian consumers. Large commercial integrators, which are primarily responsible for the fast growth of the Indian poultry sector, are providing consumers with low priced poultry products. Poultry meat and eggs provide more proteins than swine, cow milk, beef and lamb per unit of intake (GoI, 2005). Thus, greater availability and affordability of poultry meat and eggs could contribute to enhanced nutrition and poverty reduction (Dolberg, 2003; Mack et al., 2005; Permin et al., 2001), given that rural and urban households allocate more than 15 and 19 percent or their food expenditure to animal source food respectively, although primarily to milk and dairy products (GoI, 2008). The Government of India estimates that about 2 million people are employed, fully or partly, along the poultry value chain and that an increase in annual per caput availability of one egg or 50 gm or poultry meat generates about 20,000 to 25,000 full time jobs (GoI, 2005). Between 1996 and 2006, the wholesale prices for poultry meat and eggs have been declining or remained constant respectively, whereas they have increased for all other livestock commodities (Fig. 1). This suggests that supply-side factors are stronger determinants of the recent trends in the consumption of poultry products in India than demand-side factors (GoI, 2006; Rabobank, 2008).

Figure 1: Wholesale prices for selected food products in India (1996-2006).

Fig. 1 Source: GoI (2006)

The structure of India's poultry industry varies from region to region. Small-scale and integrated large-scale producers account for a growing share of output. Although it is extremely important to understand the future consumption growth in poultry meat and eggs, it has received little attention from the researchers (Sharma and Yeung, 1985; Sinha and Giri, 1989; Gandhi and Mani, 1995) both in India and abroad. There are a limited number of earlier attempts that looked into animal product consumption in India. These include Sinha and Giri (1989), examining the consumption of livestock products for three states of Gujarat, Punjab and Tripura, Gandhi and Mani (1995) discussing the importance of livestock product demand in India till the late 1980s and Dastagiri (2004), addressing some general aspects of livestock product demand using data only up to 1993. However, none of these studies offer a comprehensive picture of animal product consumption in India and they are also quite dated. An evaluation of India’s animal product consumption with the latest available data is wanted.

Market, institutional imperfections and failures constrain the sector from more effectively serving the society to reduce malnutrition and poverty in India. Large commercial producers are dominating small scale rural producers in term of product cost and efficiency (Ali, 2007; GoI, 2002). A major constraint affecting the growth of the poultry industry in India is the lack of basic infrastructure such as storage and transportation, including cold chain. This results in wild price fluctuations in the prices of poultry products, i.e., eggs and broilers. Another constraint to growth is an inefficient marketing system. The presence of so many market intermediaries harms both the producer and the consumer. A third problem relates to the price availability of feed resources. Maize or corn plays a major role in broiler production, as it constitutes 50 to 55 percent of broiler feed. As the broiler industry is growing at the rate of 15 percent per annum, the demand for maize is thus likely to increase. Presently India grows only 11 million tonnes of maize and only 5 million tonnes are available for poultry, which is not sufficient if the current growth rate of the industry is to be maintained. Large commercial integrators are unable to consistently supply rural areas because live-bird sales dominate the poultry market in India and moving live birds over long distances is prohibitively costly, due to transport, shrinkage, and mortality costs (Landes et al., 2004; Mehta and Nambiar, 2007). Low prices for poultry from large commercial integrators, therefore, primarily benefit urban consumers. As a result, urban consumers eat 2.8 and 4.5 times more eggs and poultry meat than their rural counterparts (Mehta et al., 2003).

Nutrition concern:

Nutrition being a multi disciplinary science requires the knowledge of biochemistry, immunology, physics, genetics, food science, molecular biology, microbiology, physiology, behavioural science and statistics. During last century, considerable research in poultry nutrition leads to important milestones which have been documented by Larbier and Leclercq (1994). Nutrition science has changed its emphasis from the effect of feed on the whole animal to the impact of individual nutrients on selected organs and tissues at the cellular level. The livestock feed industry is an integral and growing segment of the food supply chain. Adequate, physiologically balanced nutrition is vital to the health, fertility and optimal performance of birds which, in turn, provide a growing global human population with essential dietary protein and energy sources. Steinfeld et al. (in FAO, 2006) reviewed that bird welfare, food safety and environmental protection which is having global impact has to be considered alongside cost for production due to feed.

The science of microbiology is important as large indigenous microbial population in the gastro-intestinal tract of birds affects the host’s nutrition; influence their appetite and therefore food intake, as well as the animal’s ability to metabolize nutrients. The introduction of high-density pelletized feed operations in India has resulted in modernization and much improved production efficiency in the poultry sector. Availability of raw materials has increased in recent years due to elevated production levels of grains and oilseeds and, currently due to improved cultivation of maize varieties (Balakrishnan in FAO, 2004). Today, most poultry feed is manufactured by employing a combination of technologies i.e. grinding or rolling, heat moisture and pressure by pelleting, expanding or extruding, and applying heat via anaerobic pasteurizing conditioners. The range of raw materials incorporated into modern poultry diets is continually changing over time due to a number of factors, which were identified by Kersten et al. (2005) as price changes and fluctuations, component price dynamics, availability of raw materials, government regulatory permissions, and customer supply and demand. Information about emerging feed-processing technologies and some of the potential problems involved in achieving feed end-product quality has been documented (van der Barneveld, 2001; Thomas and var der Poel 2001 and Kersten et al, 2005). There is a direct link between animal-feed quality and hygiene issues and the safety of foods of animal origin when consumed. Therefore feed production and manufacture should be considered as an integral part of the food production chain (Tielen, 2005) and it should therefore be subjected to quality assurance and food safety systems (Manning et al., 2006a; Manning et al., 2007). The complexities of factors which determine nutrient intakes and causative reasons and hypotheses for under- or over-consumption, have been reviewed extensively (Forbes, 1995; van der Heide et al., 1999; Forbes, 2006). Birds have precise requirements for nutrients, both macro and micro, and energy-yielding components. Therefore, knowledge of their feed-intake capacity is essential if dietary concentrations are to be appropriate. An understanding of the complexities and interacting mechanisms that control feed intake is, therefore, essential in designing nutritional programmes and production systems.

The provision of quality protein devoid of any essential amino acid (EAA) deficiency is particularly critical in the early nutrition of young poultry (Dibner, 2006; Noy, 2006). There has been and continues to be research interest regarding the most deficient (limiting) amino acid in the diet and the quality of the protein mixture from which it is supplied. Amino acids represent the most costly feature of poultry diets and therefore continuous studies to establish more precise nutrient requirements are merited (Wijtten et al., 2004). Many experiments have sought to elucidate the efficiency with which EAA are utilized by the bird to support improved levels of egg, meat and broiler breeder production (Gous, 2006; Ciftci and Ceylan 2004; Kidd et al., 2004). Various interactions between vitamins, between vitamins and minerals, and between minerals, particularly trace elements as reported by Leeson and Summers, 2001 are important with regard to the nutritional integrity of diets, and which can have negative effects on poultry performance if ignored. Research focus has recently been on the dynamics of calcium utilization by laying hens (Lichovnikova, 2007) and the importance and role of selenium in the maintenance of bird health (McCartney, 2006) and broiler-breeder fertility (Renema and Robinson, 2006).

Poultry disease and prevention:

Rapid growth due to genetic selection, intensive feeding and management systems are the main cause of various skeletal disorders and metabolic diseases causing mortality (Julian, 1998). Gardiner et al. (1988) found a clear relationship between body weight and mortality, in particular to mortality caused by the Sudden Death Syndrome (SDS). Differences between breeds in mortality have also been reported by many authors (Tarrago and Puchal, 1977; Neupert and Hartfiel, 1978; Proudfoot et al., 1979; Seemann, 1981; Ehinger, 1982; Sailer, 1985; Grashorn, 1987; Bergmann et al., 1988). It is also well documented that in male broiler (which grow faster than females) the mortality is about twice as high as in females (Cassidy et al., 1975; Seemann, 1981; Proudfoot et al., 1982; Bergmann et al., 1988; Greenless et al., 1989; Hulan et al., 1989). One of the most important causes of mortality in modern broilers is SDS, and in some countries ascites. The peak of both mortality from SDS and ascites is usually after the second week of age. It has been reported that various management and feeding measures such as feed restriction, lighting programmes, mash vs. pellet feeding and low protein and energy diet reduces early growth and level of mortality in broilers (Gardiner, 1971; Hulan and Proudfoot, 1981; Scholtyssek, 1987; Tiller, 1984; Petersen, 1988).

Skeletal disorders and leg weakness is a very common problem in poultry industry. Chondrodystrophies which is characterised by decreased bone mineralisation and increased porosity of cortical bones (Williams et al., 2000) is caused by nutrient deficiencies. Femoral head necrosis (FHN) is a severe degenerative disorder affecting mature broilers. Though outwards sign of leg deformation is lacking, they are reluctant to walk and while walking they place their wing tips on the ground to support themselves. It has been reported that coagulase positive staphylococci are mainly responsible for FHN in bacterial osteomyetitis (Thorp et al., 1993). Synovitis which is characterised by arthritis may be of bacterial or viral origin (Reece, 1992). Infectious stunting syndrome (ISS) also known as runting and stunting syndrome, pale bird syndrome or ‘helicopter disease’ is caused by picornavirus-like particles (Reece and Frazier, 1990). This condition is characterised by poor uneven growth and sometimes accompanied by sighs of enteritis. Bone deformity or Angular limb deformity characterised by either outward or inward angulation of the limb at the intertarsal joint is the most common long bone distortion seen in broilers. Dyschondroplasia, tibial dyschondroplasia and rickets are a few bone diseases caused in poultry. Provision of adequate dietary calcium, phosphorus and vitamin D will prevent rickets under normal conditions, in the absence of malabsorption syndromes. Degenerative disorders of joints occur in broilers but are usually more prevalent in birds grown to greater ages and weights for breeding purposes. In older birds, destructive cartilage loss or osteoarthrosis in the hip joint is common (Hocking et al., 1996). These problems are less apparent in feed-restricted birds. This finding may indicate that continuous genetic selection for fast growth is resulting in poorer bone quality especially in mail birds which grows faster.

Avian muscle is similar in structure with mammalian tissue. The circulating activities of a number of enzymes are raised in muscle damage or myopathy. These enzymes include lactate dehydrogenase, aspartate aminotransferase (AST) and aldolase. Creatine kinase (CK) is most commonly used for the diagnosis of muscle damage because of its very high activity in and high specificity for muscle. This enzyme has been widely used in the diagnostic interpretation of various avian pathologies (Siller et al., 1978; Hollands et al., 1980; Tripp and Schmitz et al., 1983), acute heat stress (Ostrowski-Meissner, 1981) and transportation stress (Mitchell et al., 1992). Elevation in the circulating concentration of troponin T is taken to be specific for heart muscle damage. Deep pectoral myopathy (DPM), Oregon disease or green muscle disease is a degenerative myopathy of the deep pectoral muscle in broilers and turkeys. The muscle is inflamed and oedematous with localised haemorrhages, pigmented green and contains large amounts of necrotic tissue. The problem is caused by ischaemia during exercise caused by raised intramuscular pressure. It is accompanied by large increases in plasma CK and AST activities (Siller et al., 1978). Muscular dystrophies in broilers can have either genetic (Hudecki et al., 1995) or nutritional causes. Nutritional muscular dystrophy is caused by deficiencies of antioxidants, particularly vitamin E and selenium (Cheville, 1966; Hassan et al., 1990). Ascites in broilers is characterised by a dilatation and hypertrophy of the right side of the heart, affecting both the atrium and the ventricle. It develops rapidly, and typical signs are cardiac failure and several changes in liver function, causing an accumulation of ascitic fluid, with or without fibrin, in the abdominal cavity (Riddell, 1991). It mainly affects fast growing broiler chickens, and is known to be the primary cause of death in birds reared at high altitude (Maxwell and Robertson, 1998). Maxwell and Robertson (1998), in a worldwide survey in 1996, estimated the incidence of ascites to 4.7 %, which makes it one of the major causes of death in broilers.

Sudden Death Syndrome (SDS) is a major cause of mortality in broilers and was first described in the early 1980s. It is characterised by sudden vigorous wing flapping, muscle contractions and obvious loss of balance. In the final phase the birds fall on their back or to the side and die. Because of the rapidity of the death and the typical posture of the dead birds (80 % are found lying on their backs; Bowes and Julian, 1986), SDS has also been called “sudden death” or “flip-over-syndrome”. Infectious Bronchitis (IB) is a viral disease which is characterised by lesions in the respiratory system (trachea, bronchi, lungs and air sacs), and can infect kidneys, and the ovaries in adults, producing intense respiratory symptoms (King and Cavanagh, 1991). Avian Pneumovirus infection was first described in turkeys. In broilers this pneumovirus infection is associated with the so called Swollen Head Syndrome with sinus inflammation and blindness, and sometimes signs of nervous dysfunction with twisted necks. Mycoplasma gallisepticum is the predominant mycoplasma infection in Chronic Respiratory Disease (CRD). It affects bronchi, lungs and air sacs. It also affects several production parameters, and makes the birds more susceptible to other diseases and infections, such as IB, Avian Pneumovirus infection and E. coli (Stipkovits et al., 1993).

Poultry genetics and breeding:

Research funds are very limited for poultry research. The Central Avian Research Institute (CARI) and Project Directorate on Poultry (PDP) are premier poultry research institutes, dedicated to implement different poultry breeding research programmes related to egg and meat type chicken. The mandate assigned to PDP and CARI are to coordinate and monitor ICAR sponsored research programmes and to undertake applied research on genetics and breeding of poultry and conservation of improved poultry germplasm with supporting research on other aspects. As a result molecular breeding will totally change our current practices of selective breeding for different species of poultry. It is expected that methods of assessing the genetic variability at the genome level rather than at the phenotypic level will be the basis of selective breeding within next 10 years. Molecular basis of poultry phenotypes will be used to engineer and re-design the poultry genome with novel technologies and genetically engineered poultry stocks for egg and meat production. Poultry has been the research material for many advance biotechnological works. Many research works carried out on poultry had bagged the Noble Prizes. Among the major contributions from poultry are; the first evidence for viral induced tumor came from chicken (Nobel prize, 1966), reverse transcriptase enzyme was isolated from Avian Leukosis virus (Nobel Prize, 1975), oncogenes in virus are from host cells (Nobel Prize, 1989) and major two arms of immune response, the T and B cells were first discovered in chicken. The chicken cells may also serve as suitable model for production of antibodies. With the changing scenario of research and development poultry is now emerging as a bio-factory for production of various pharmaceuticals, vaccines and proteins of foreign origin. The characteristics such as high rate of prolificacy, easy handling, short generation interval, comparatively economic maintenance, easy procurement, ease in preparation of primary cell cultures, dichotomy of immune system and nucleated erythrocytes make the chicken a suitable animal model for immunogenetic and molecular studies.

Molecular techniques to identify and specify quantitative trait loci (QTL) have advanced rapidly. Functional genomics where we study expression patterns of multiple genes simultaneously is helping to expose the further gaps between genotype and phenotypes. Presently there is increasing interest in breeding for increased disease resistance. With the availability of the draft chicken genome sequence, the genes that underlie the resistance loci can be identified and utilized. Proteomics will soon become as important to poultry researchers as it has to human researchers.

The main objectives while breeding of layers are to increase efficiency of egg production per hen housed, optimal external and internal egg quality, low feed cost per egg or per kg egg mass and low mortality and high adaptability to different environment. Genetics progress might be possible due to high positive genetic association between part and total egg production (Mallikarjuna, 1998). Micro satellite markers and expressed sequence tags are useful tools to enhance continuous selection. Feed efficiency can be utilised to reduce feed cost. Residual feed consumption (RFC) was first introduced in laying hen where it is used in the selection of commercial lines since many years. The QTL approach is expected to bring new data on the genetic control of appetite and variability of RFC. Disease resistance is often cited as the next great challenge facing poultry geneticists. Immunization against infectious diseases has proven to be one of the most cost-effective methods of controlling economic losses in poultry. Unfortunately, even today poultry birds continue to suffer from a large number of infectious diseases out breaks. Disease resistance is usually mediated by innate and acquired immunity. It is unlikely that disease resistance will be the sole selection criterion, thus resistance trait will need to be included in the overall-breeding goal.

DNA plays an essential role in bird’s system. It is the master molecule that contains the most essential information to propagate cells, organs, and the bird itself. The major detriment to molecular genetics at present is cost and speed of the analysis. However, as the technology progresses, expense can decrease by orders of magnitude in a few years now. Molecular genetics could greatly benefit the behaviour traits. Poultry welfare issues are becoming a major concern that poultry breeders will need to address in future. Selection to improve poultry well-being is difficult and requires either direct measurement of traits related to well being or indirect measurement using group selection. Research is urgently needed to better understand in elimination of cannibalism, aggression, panic behaviour and the consequences of the unbalanced-ness of the modern layer as compared to its wild ancestor. Genomics could well play a key role in this, both in unraveling the biological mechanism and in supporting the poultry breeders in selection programs. It will be more important for future layer breeders to include a variety of possible production environments in breeding strategies. Elson (2002) in an article on poultry industry development from 1962-2012, mentioned about the possibility of abolition of cage management system in many of the European countries due to pressure applied by the animal welfare activities. Considering the changing scenario of poultry management system, the recording of eggs will become more cumbersome job in future. Therefore, under present circumstances there is a growing interest for floor laying type due to possible ban on cage production.

The major constraints on applying biotechnologies have been enumerated by Madan (2003) which are absence of an accurate and complete database on livestock and poultry owners so that programmes can be implemented. The fact that many poultry species and breeds are unique to the developing world; each has its own distinct developmental, production, disease resistance and nutrient utilization characteristics.

CONCLUSION:

Poultry has served mankind in different ways. Apart from being the source of high quality and nutritious proteins, poultry has significantly contributed in research and development activities. Feed optimization, regular up gradation in feed micronutrient composition and maintenance of hygienic conditions in cages can avoid some of the poultry welfare issues and certain diseases. Poultry death due to infections disease is one of the major threat and challenge in poultry industry. Further research in this aspect is needed in order to create disease resistant birds. Recent biotechnological techniques hold great promises for diversified use of poultry. These newer techniques may provide safe and efficacious tools for disease management and more precise tools for estimation of genetic variability for improving production or disease resistance. Genetic modification methods may pave the way for diversified use of poultry as well as may lead to new horizon of poultry production. The future research strategies may, therefore, be focussed on identification of QTLs through genome wide scan, microarray analysis for elucidating the biological pathways and deciphering the genes involved in particular biological event/process, allele mining for identification of new but useful alleles having effect on phenotype. The genetic modification through driven approach like transgenesis and knocking down a gene and other approaches like RNAi and use of CpG motifs also hold great promises not only for augmenting poultry production and protection but also for diversified use of poultry. Recently, uses of recombinant cytokines as immuno-modulator, adjuvant and growth promoter have been advocated. These biotechnological tools used in combination with breeding methods may help in developing the genetically robust stocks having higher production level.

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Received on 10.05.2011

Modified on 12.05.2011

Accepted on 17.05.2011

Research J. Science and Tech. 3(3): May-June. 2011: 129-136