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Abstract
1. Genetic parameters were estimated in a base population of a closed experimental strain of fowl. Data were obtained on 21 245 Iranian native hens (breeding centre for Fars province) subject to 8 successive generations of selection. This population had been selected for body weight at 12 weeks of age (BW12) and egg number during the first 12 weeks of the laying period (EN), mean egg weight (EW) at weeks 28, 30 and 32, and age at sexual maturity (ASM).
2. The method of multi-traits restricted maximum likelihood with an animal model was used to estimate genetic parameters. Resulting heritabilities for BW12, EN, EW and ASM were 0·68 ± 0·02, 0·40 ± 0·02, 0·64 ± 0·02 and 0·49 ± 0·02, respectively.
3. Genetic correlations between BW12 and EN, EW and ASM were 0·11 ± 0·33, 0·54 ± 0·21 and −0·12 ± 0·03, respectively. Genetic correlations between EN and EW and ASM were −0·09 ± 0·03 and −0·85 ± 0·01, respectively, while between EW and ASM, it was 0·05 ± 0·03.
4. The overall predicted genetic gains, after 7 generations of selection, estimated by the regression coefficients of the breeding value on generation number were equal to 22·7, 0·17, 0·04 and −1·38, for BW12, EN, EW and ASM, respectively.
5. A pedigree file of 21 245 female and male birds was used to calculate inbreeding coefficients and their influence on production and reproduction traits. Average inbreeding coefficients for all birds, inbred birds, female birds and male birds were 0·048, 0·673, 0·055 and 0·047%, respectively. Regression coefficients of BW12, ASM, EN and EW on inbreeding coefficient for all birds were equal to 0·51 ± 0·001, 0·31 ± 0·003, −0·51 ± 0·003 and 0·03 ± 0·001, respectively.
Acknowledgements
This research was carried out at the Animal Science Research Institution of Iran and Department of Livestock Affairs, Ministry of Jihad-e-agriculture and with the help of Shiraz University (Department of Animal Science). Finally, we thank M. Sargolzaei for kindly providing the ‘PEDIGREE’ program.