General management
The study was conducted at Bangladesh Livestock Research Institute, Savar,Dhaka to estimate the selection response of Non-descript Desi (ND), Hilly (H) and Naked Neck (NN). Day-old chicks collected from the hatchery were weighed and leg banded individually. After that all the chicks of three genotypes were transferred into the brooder, which were cleaned and disinfected earlier. One-week later leg bands were removed and wing bands were provided all the experimental birds and 5% glucose solution was supplied for the first three days. The chicks were brooded and reared up to 16 weeks of age with individual wing band in a brooding and growing house with standard feeding and management. The photo period for brooding period was started at 24 hours/day reduced @ 1 hour/week. Depending on season and day length photo period was also maintained for layer birds. All the chicks were vaccinated as per schedule suggested by the veterinarian. After 16 weeks of age all female and male birds were transferred into individual cage. Artificial Insemination was practiced and male and female ratio was maintained as 1: 6 for all genotypes.
Basis of selection
Records obtained from 359 progeny for Non-descript Desi (ND), 235 progeny for Hilly (H) and 296 progeny for Naked Neck (NN) belonging to 3 generations (2004-2006). In each generation, selection was performed two times i.e. first time at 16 weeks of age on the basis of body weight and physical appearance and second time at 40 weeks of age on the basis of egg production, egg weight, sexual maturity and body weight using selection index and individual culling method. The target of selection is mainly to increase egg production 2% per generation and to increase egg weight 1 gm per generation. In each generation, 40 to 46% birds were selected for ND, H and NN. As a part of breeding activities individual records were kept to evaluate the individual performance. Data has been collected from the genotypes on the basis of the following selection index parameters:
- Age at sexual maturity (days)
- Body weight (g) at 40 weeks of age
- Egg production (%) (168-280 days)
- Egg weight (g) at 40 weeks of age
The selection Index was computed by the following equation:
Selection Index (I) = b1x1 +b2x2 +…………. + bnxn
Where; x1, x2,…….xn represent the phenotypic value for the trait
b1,b2,…….bn denote the relative weight given to each of the trait
Expected response to selection estimation
Expected Response in three types of native chicken for egg production, egg weight, body weight and age at sexual maturity was estimated for each generation using following equation:
R =1/2 h2 × Sf
Where,
(R) = Expected Response in mass selection
h2 = heritability, h2 of EP, EW, ASM and BW was considered as 0.15, 0.50, .40 and .50 (Poultry Breeding Manual)
Sf = Selection Differential for dam).
Data recording
Data for egg production, egg weight, age at sexual maturity and body weight were recorded. Daily egg production was recorded twice a day (11:00-12:00 AM and 3:00-4:00 PM). Egg weight was recorded individually at 40 weeks of age for five consecutive days and calculated the average egg weight. All the eggs were identified individually. On the basis of data collected hen-day egg production (HDEP %) was calculated for 23th week to 52th week.