Multitrait index selection without restriction and with different levels of restriction in broiler dam line pullets

This study was conducted on 1663 progeny produced from 40 sires of brioler dam line. The traits recorded were 5^/-nucleotidase (5^/-N), intestinal alkaline phosphatase (IAP) and glutamate pyruvate transminase (GPT) enzymes at 6 weeks of age and body weight at 6 weeks of age (BW6), and at 20 weeks of age (BW20), age at first egg (AFE), egg production upto 40 weeks of age (EP40) and egg weight at 32 weeks of age (EW32). The data were analysed by using Harvey's mixed model least squares technique. One hundred twenty multitrait selection indices were constructed combining seven traits (excluding GPT) in all possible combinations considering aggregate genotype of BW6, BW20, AFE, EP40 and EW32 with selection intensity as 1.40. Twelve restricted selection indices were also constructed imposing 100, 50 and 25 per cent restriction on BW20 and AFE individually as well as in combinations simultaneously, to avoid undesirable change in these traits. The index IR₈ combining BW6, BW20, AFE, EP40, EW32, 5^/-N and IAP with 100 per cent restriction on BW20 was considered to be the best index having heritability and R_IH value as 0.895 and 0.825, respectively. Through the application of this index response per generation would be 46.94g, 0.00, -1.32 days, 3.23 egg and 0.48g. in BW6, BW20, AFE, EP40 and EW32, respectively.