Formation of foundation stock
Bangladesh Livestock Research Institute (BLRI) since its inception did initiate programs for the conservation and development of Indigenous Chicken through several poultry development projects. As a part of selection and improvement of indigenous chicken, the Poultry Production Research Division (PPRD) of BLRI to date collected 5 types of Indigenous Chicken to continue the said breeding program. But during those phases selection was performed mainly on the basis of phenotypic characteristics of birds. The individuals were not selected on the basis of their selection index value/breeding value.
Selection criteria
In foundation generation and in 1st and 2nd generation, selection were practiced at 2 (two) stages of birds life, firstly at 8 weeks of age, selection was performed on the basis of breeding value for 8 week body weight and secondly, at 40-weeks of age, on the basis of an index comprising the following traits: i) Age at first egg (days) ii) Body weight (g) at 40 weeks of age iii) Egg production (%) at 168-280 days iv) Egg weight (g) at 40 weeks of age
Multi-trait selection
The maximum economic merit of an individual can not be assessed by evaluating it on the basis of only one trait. The choice of traits becomes complicated when the traits chosen are negatively related at genetic level. Traits also differ in heritability and their economic values. Therefore, to optimize all these factors Selection Index proposed and developed by Hazel (1943) giving due weight-age to genetic correlation, heritability and economic worth was used.
Statistical analysis
The data used in the present study were from three different genotypes and sample sizes were unbalanced. The number of birds varied from class to class and subclass to subclass. Hence, it fulfilled the characteristics of a non-orthogonal factorial design and all recorded data were analyzed by General Linear Model (GLM) procedure using SPSS 11.5 for Windows. For all statistical purposes the theory of Snedecor and Cochran were followed.
Birds were arranged based on generation, genotype, batch and sex. Initially, the general linear model (GLM) procedure of SPSS 11.5 was used to adjust all fixed effects as well as to test all possible full linear models. Duncan’s multiple range test (DMRT) was used for mean comparisons.
Prediction of expected selection response
Expected genetic progress due to selection in a generation for egg production, egg weight, body weight and age at sexual maturity was estimated for G0, G1 and G2 using the following equation.
R =1/2 h2 × Sf
where,
R = Expected response
h2 = heritability of EP, EW, AFE and BW
Sf = Selection differential for the selected females
For 8 week body weight,
R = h2 × S
where,
R = Expected response in mass selection
h2 = heritability of 8 week body weight
S = Selection differential.