Ram Singh Bibyan, Satish Kumar Rathee, Prajakta Kailas Sangale, Jannat Saini, Lovely Anant, Priyanka Patir and Harneet Kour
Animal Nutrition Division
ICAR- National Dairy Research Institute
Karnal- 132001 (Haryana) India
Email: carirsingh@yahoo.co.in
Mobile No. +91-9457602079
There is very basic philosophy in animal breeding that mating of best with best produce the best. Identification of superior animals based on production performance or phenotype, for breeding is known as selection and has been practiced for ages. Advancement in scientific knowledge in animal breeding has led to the expansion of poultry farming in last few decades. Currently, the genetically superior stocks having higher production potential, even under adverse climatic conditions, has transformed poultry sector from rural farming to full-fledged industry. Increase in productivity per bird is attributed to the combined crossbred and purebred selection (CCPS). Additionally, temperature is also the most important environmental factor affecting poultry production. Elevated temperature leads to reduced productive performance in both broilers and laying hens, particularly when accompanied by high relative humidity. High ambient temperature in tropical and subtropical regions adversely affects the growth and egg production performance in both broiler and laying chickens, respectively. Relative humidity and ventilation rate influence bird’s performance, particularly when they are reared in open sided poultry houses. Genetic approaches that aid in reducing or altering the extent of plumage cover has resulted to adopt in many hot regions. Fortunately, there are some major and marker genes which can reduce the deleterious effects of heat stress. Naked neck (Na) and frizzle (F) genes are the most notable. Therefore, the naked neck and frizzle genes can be a viable alternative for broiler and layer production particularly, in the tropical countries where summer temperatures are very high. Indigenous birds have desirable traits such as disease resistance; pleasantly flavoured meat and eggs, and the ability to cope up with adverse environmental conditions. Crossing indigenous strains with exotic commercial ones have the advantage of high egg production in the exotic strain and the adaptation of the indigenous strain to the Indian environment. Currently, efforts are on to improve the egg production of native chickens through crossbreeding.
Layers: For layer, the prime objective is “To obtain maximum number of saleable eggs per hen housed at low feed cost per egg or per kg egg mass and the eggs should have optimal internal and external qualities. Stock should have low mortality and high adaptability to different environments”. Breeders today select the poultry birds for the age at sexual maturity, the rate of lay, livability, egg weight, body weight, feed conversion efficiency, shell color, shell strength, albumen height, egg blood and meat spots, bird temperament, disease resistance and skeletal problems (osteomalacia and osteoporosis).
Broilers: For broilers, the breeding strategies concentrate on rapid growth and carcass traits. Different breeding and selection technologies at different period of time were employed for the genetic improvement of broilers. Breast muscle weight, meat quality and feed conversion rate (FCR) are major traits; in addition to these, thrust is also being given on skeletal abnormalities, metabolic disorders and welfare. The selection based on breast area measured through length and width of the breast using a pachymeter along with body weight resulted in a genetic gainof 277% per generation while keeping feed conversion and fertility in the actual levels. The nondestructive means like needle catheters, ultrasonic apparatus etc. were found more accurate for measuring the thickness of the breast muscle. The other non-invasive methods like computed tomography scan (CT scan), magnetic resonance imaging (MRI), and echography are more accurate for measuring the muscle thickness and dimensions of internal organs etc., but these methods are more expensive. Therefore, among the various non-invasive means, ultrasound offers a viable and advanced solution for breast muscle analysis.
Most of the high yielding exotic breeds have temperate origin or have been developed in temperate climatic conditions. India being a tropical country having vast hot and humid area around coastal regions is not suitable for full expression of its production potential. In the peak summer and humid months, high yielding stocks suffer from decreased feed consumption, low egg production and reduction in the feed efficiency. The egg quality is also being affected in these months. It is therefore desirable to produce and develop birds which will be suitable to the tropical environment. Heat tolerance can be improved through:
- more efficient thermoregulation
- through enlarged naked body surface
- lowering basal metabolism
- reduced feathering intensity
- creating specific colours by obtaining skin having melanin and non-pigmented feathers.
In last two decades, several major genes were identified which can be utilized for productive, adaptability to tropical climate and management conditions. Direct and indirect effects of some of such genes have been presented in table-1.
Table 1. Tropical relevant genes in local fowl
| S No. | Gene | Nature of inheritance | Direct effect | Side effect |
| 1. | dw (Dwarf) | Sex linked recessive &multiple allelic | Reduction in body weight (10-30%) | Reduced metabolism, improved fitness and disease tolerance |
| 2. | Na (nacked neck) | Incomplete dominant | Loss of neck feather, Reduction of secondary feathers | Improved ability for convection, improved adult fitness |
| 3. | F (Frizzle) | Incomplete dominant | Curling and reduction of feathers | Improved ability for convection |
| 4. | H (Silky) | Recessive | Lack of hamuli on the barbules, delicate shaft, long barbs on the contour feathers | Improved ability for convection |
| 5. | K (Slow feathering) | Dominant, Sex linked, multiple allelic | Delay of feathering | Reduced protein requirement, reduced fat deposition during juvenile life, increased heat loss during early growth, delayed immune response mechanism |
| 6. | Id (Non- Inhibitor of dermal melanin) | Recessive, sex multiple allelic | Dermal melanin deposition on skin and shank | Imnproved ability for radiation from shank and skin |
| 7. | Fm (Fibromelenosis) | Dominant with multifactorial modifiers | Melanin deposition on all over body, muscles and nerves, Imnproved ability for radiation from shank and skin tendons, mesenterium and blood vessel walls | Protection of skin against UV radiation, improved radiation from the skin, increased pack cell volume protein |
Systematic studies for identification of various genomes and major genes in our indigenous breeds are lacking. Attempts have been made to study some of the breeds at ICAR- Central Avian Research Institute, Izatnagar (bareilly) under the International collaborative project entitled “Evaluation of poultry genetic resources for creating genetic stock with improved adaptability, productivity and disease resistance in tropical environment”. Breeds/ecotype studied were Aseel, Kadakanath, Naked neck and Frizzle fowl.
Aseel: Aseel is a game bird well known for its pugnacity, high stamina, majestic gait and dogged fighting qualities. The remarkable endurance of Aseel during the most critical stages of fight is proverbial because it prefers death to dishonour. Aseel is also known for its plentiful delicious and flavoured meat. Being a game bird, it is considered to be the strongest and hence capable to tolerate the tropical stress. Being the largest bird among the native breeds and having the broader breast. This breed has been utilized for the development of exotic broiler breed.
Kadaknath: Kadaknath, locally known as ‘Kalamansi’ (having dark grey/blue meat) is an unique type of poultry breed of Madhya Pradesh. The skin, beak, shank, toes, soles of feet of males and females are dark grey colour. Even the comb, wattles and tongue also show a purplish hue. The shining blue tinge of the earlobes adds to its unique feature. The peculiarity of this breed is the black colour of muscles and tissues due to a rare genetic condition “Fibromelanosis”. The major genes identified in this breed are Slow feathering (K), silver gene (S), presence of recessive allele of inhibitor dermal melanin (id), presence of recessive allele of barring gene (b) and dwarf gene (dw) in the sex linked group and genes for fibromelanosis (Fm), recessive allele of dominant epistatic gene (i), mottling gene (mo) and lacing gene (la) in autosomal group.
Naked neck and Frizzle fowl: Naked neck and frizzle fowl ecotypes are available in vast coastal regions of the country including Andman and Nicobar and north eastern regions. As the name indicates these ecotypes have naked neck and frizzle genes.
Utilization of major genes at CARI, Izatnagar: Some of these genes have been successfully interogressed in the high yielding layers and broilers to increase the topical adaptability.
Naked neck (Na): Naked neck condition is caused due to an incompletely dominate gene (Na) that causes loss of neck feathers and reduction in the intensity of feathering from 30 to 40 % and thus helps in better heat dissipation and improved topical adaptability. Significant desirable effect of this gene is observed at 300C or higher environmental temperature. Due to low protein dietary requirement during juvenile growth and better topical adaptability, this gene has been utilized for the development of high yielding broiler CARIBRO (named after Central Avian Research Institute (CARI & Broilers), Mrityunjay and high yielding naked neck White Leghorn.
Frizzling (F): The frizzle gene (F) is an incompletely dominant autosomal gene which causes curvature in the rachis of feathers that curve outward away from the body and thus room between two feathers are made which helps in better heart dissipation. In homozygous, the curving is extreme and the barbs are extremely curled so that no feather has flat van and heterozygous have less curling. This gene is mostly useful in arid zones where there is chance of sunburn if naked neck is used. This gene has been utilized for the development of CARI Tropicana broiler, which possess both Na and F genes, and high yielding frizzle White Leghorn.
Slow feathering (K): Slow feathering (K) is a sex linked dominate gene, which is related to tropical adaptability and can be used for the day old sexing of chicks. This gene was identified in Kadaknath breed of native chicken and Jamuna strain of slow feathering line was developed for day old sexing.
BL-B II gene clone: BL-B II region of MHC of Aseel bird was cloned and sequenced. The knowledge of BL-B II gene sequence will be of much help in disease resistance as well as in characterization of MHC region of native germplasm. For a successful genetic improvement programme in poultry, we must consider a balance of characteristics related to growth as well as reproduction. Utilization of these specialized sire and dam lines in commercial layer and broiler enterprises minimizes the production cost and the gene recombination in these crosses produced a heterotic effect in progeny for different economic traits. While practicing the artificial selection, care is taken to minimize the inbreeding, to avoid its consequences in the population.