Comparing Slow-Growing Chickens Produced by Two- and Three-Way Crossings with Commercial Genotypes. 1. Growth and Carcass Traits

Abstract

This study compared growth and carcass traits of slow- and medium-growing chickens produced by two- and threeway crossings with those of commercial fast- and slow-growing chickens at 8, 10 and 12 weeks of age. In total, 2,240 mixed male and female day-old chicks from each of six different genotypes [two-way crossings (S1 and S2), threeway crossings (S3, S4, S5 and S6), commercial fast-growing (F), commercial slow-growing (CS)] were randomly allocated among four compartments of the same house.The rapid growth occurred in the commercial fast-growing F genotype (1,985 g at 42 days), followed by the S3 and S4 three-way crossings (2,294 g and 2,268 g, respectively at 49 days), the S1 and S2 two-way crossings and the commercial slow-growing CS genotype (1,946 g, 1,988 g and 2,100 g, respectively at 56 days) and the S5 and S6 three-way crossings (2,175 g and 2,079 g, respectively at 84 days). The F genotype had the highest live weight and lowest feed consumption at 8, 10 and 12 weeks, followed by the S3 and S4 genotypes, the CS, S1 and S2 genotypes, and the S5 and S6 genotypes (P < 0.05). Live weight and feed consumption increased and feed-conversion ratios worsened with increasing slaughtering age (P < 0.05). F genotype birds had the highest dressing percentages and breast ratios (P < 0.05), whereas the two-way crossing S1 and S2 genotypes had the highest abdominal fat ratios(P < 0.05) and the three-way crossing S5 and S6 genotypes had the highest leg ratios. Leg ratios of the commercial CS and two-way crossings S1 and S2 genotypes were similar. Carcass traits and abdominal fat ratios differed significantly by age (P < 0.05). © Verlag Eugen Ulmer, Stuttgart.