Udk = 636.5:636.084.1 Evaluation of Growth and Carcass Traits between 42 and 58 Days of Age in Chickens Divergently Selected for Body Weight

The effect of divergent selection for high (H) or low (L) body weight at eight weeks of age for 25 generations on growth and carcass traits between 42 and 58 days of age was studied. The chicks were reared in individual cages under standard management conditions. Selection for low 8-week body weight has resulted in higher relative body weight increase for the period from 42 to 58 days of age compared to chickens from the high line. Body weight increased by about 72 % in the low line and by about 56 and 44 %, respectively in the males and females in the high line. In both lines of chickens dressing out percentage and the percentage of abdominal, subcutaneous and total fat increased with body weight, whereas percentage of m. pectoralis superficialis and m. pectoralis profundus remained roughly constant. Percentage of skin decreased with increasing of body weight. In both lines females had a higher percentage of total fat than males. There was evidence that total fat content increased independently of animal body weight with a certain age. Fixed age comparisons of feed conversion ratios showed no differences in feed conversion between the two divergently selected lines of chicks.