Introduction
The domestication of jungle fowl marked the beginning of selective breeding of poultry. The breeds showed a range of traits, including production traits such as body size, musculature, egg production, and egg color. Industrial breeding started with the hybridization of selected pure breeding lines sampled from these base breeds and continued with a more and more intense further selection of the pure lines. The different breeding and selection technologies at different periods of time for the genetic improvement of poultry were introduced. Techniques such as Mass selection, Hybridization, Pedigree selection, Artificial insemination, Osborne index, Family feed conversion testing, Selection index, Individual feed conversion testing, BLUP breeding value estimation, DNA markers are used over decades.
Genetic Strategies for the Improvement of Broilers
Breeders set breeding goals as a reflection of their expectations of future market demands with the ongoing changes of production and consumption trends. Broiler growth (body weight) has consistently been the prime selection trait, Family selection for livability and eradication of egg-transmitted diseases at the pedigree level may have contributed to the reduction of mortality. Indirect carcass measurements (breast muscle thickness) were applied to the male selection. In direct measurements, the sib information was used in the index, there is a higher intensity of selection which in turn increases the rate of inbreeding. Whereas, indirect carcass measurements provide their own performance information for the selection of candidates, which increases the accuracy of selection and consequently improve the genetic gain. It also reduces the rate of inbreeding.
Genetic strategies for ascites in broilers
Ascites syndrome has been a source of concern to the poultry industry. The genetic selection is the best solution for eliminating ascites syndrome in near future. With the advent of molecular genetic research on the genetic basis of ascites, we can see the potential for the identification of genetic markers that can be used to eliminate ascites from modern commercial broilers.
Genetic strategies for heat stress in broilers
Heat stress is one of the most important environmental stressors challenging broiler production worldwide. With the rapid development of the poultry industry worldwide, importation of high-performance stocks to, hot regions are continuously increasing. The use of improper genotypes in these regions results in large economic losses due to decreased growth rate, reduced protein gain and high mortality. Three major genes associated with heat tolerance were identified in poultry and they were naked-neck gene (Na) (reducethe feather coverage), frizzle gene (F) (modify the shape of the feather), and dwarf gene (dw) (reduces body size). Among these three genes, most notable is the gene for naked neck (Na), which produces heat tolerance by reduced feather coverage thereby increasing the rate of heat dissipation. Hence, specialized breeding programs using specific indicators of adaptation to heat should be added to commercial selection programs for rapid growth to improve broiler performance in hot climates.
Genetic strategies for layer improvement
Egg production has always been important for the selection criteria applied to egg laying stock. Egg numbers have increased from less than 270 to 340 eggs due to advancements in genetics. Traditionally part record selection was advocated as a means of shortening generation interval to increase genetic progress. Recently apart from part-production, annual production is also taken into account for selection decision. However, use of the whole record will double the generation interval. In order to optimize genetic gain/unit of time multi-stage selection is followed as it reduces the cost and efforts (by discarding inferior birds at early age) and generation interval is minimized.
Selection strategy egg production and for feed consumption
In layers improved feed conversion throughout the 20th century by selection on increased egg mass production and smaller body size. They are the most important traits involved in the variation of feed consumption. The most commonly used criteria for feed efficiency in laying hens are daily feed intake per hen, feed intake per egg, feed conversion (kg feed per kg egg mass), and egg income minus feed cost. Commercial poultry geneticists have also been selecting on residual feed consumption for improving feed efficiency. From the majority of the selection experiments from large commercial populations, it is apparent that most laying hens have a remarkable ability to adjust their feed intake to requirement. However, a significant residual component of feed intake has been shown to exist hence in recent years, because of high heritability and absence of significant negative effect on production parameters, residual feed consumption is used as selection criteria to improve feed efficiency.
Egg quality traits and its improvement strategies
Eggshell quality traits, amount of cuticle, color of eggs, protein content of eggs, gene for vitelline membrane, and traits related to aesthetics in eggs all are under selectable genetic control. Whereas a completely separate breeding programme exists for the production of white and brown-shelled eggs. Practicing selection for egg quality will continue to be one of the most important aspects of the breeding strategy for egg-laying hens. Genetics and genomics have identified new strategies to address egg quality including the use of very high-density genotyping to allow genome-wide selection which has potential benefits for measurements that can be performed in one sex.
Breeding for Diseases Resistance in Broilers and Layers
Salmonellosis, campylobacter, Marek’s disease, Newcastle disease avian influenza, and infectious bursal disease significantly affect the economy of the poultry sector. New opportunities have been arising in animal genomics and related technologies. With the availability of the draft chicken genome sequence, the genes that underlie the resistance loci can be identified and utilized. In recent years, advances in molecular genetics, the relationship between genes and their corresponding phenotypes, are beneficial for disease prevention and control. Most of recent strategies are now developed, combining structural, population, and functional genomics approaches.
Also, read | Poultry Breeding: Recent Molecular Approaches, Breeding Programmes, and Selection Methods
Conclusion
Genomics in poultry breeding has seen notable progress. The search for new measurements that more reliably reflect the traits which are the ultimate target of selection, whether it is a reduction in bacterial contamination, the resistance of the shell to damage or processing and nutritional qualities will be a major focus. In the future genomics could well play an important role in supporting breeders in selection programs. This will affect the structure of breeding programs and also impact the integration of breeding in the poultry production system. The new knowledge of the molecular basis of poultry phenotypes that are generated along the way will be used to engineer and redesign the poultry genome with novel technologies, and genetically engineered poultry breeds.
Authors:
Suyesha Kadam ¹*, Shriya Bhatt¹, Manas Arora¹, Mohit Bharadwaj2 and B.C. Mondal3
¹M.V.Sc. Scholar, 2PhD scholar and 3Professor
Department of Animal Nutrition, College of Veterinary and Animal Sciences, GBPUAT, Pantnagar, US Nagar, Uttarakhand-263145
*Corresponding Author Mail id: – Suyeshad26@gmail.com
