Selection for body weight at eight weeks of age. 20. Production traits and the B and C alloantigen systems

The current study evaluated influence of genotypes of the B and C alloantigen systems on production traits in lines of White Plymouth Rock chickens. Lines had been selected previously for high (HWS) or low (LWS) 8-wk BW and after 27 generations of selection, a random sample of each selected line was used to initiate subpopulations in which selection was relaxed. For the present study, blood typing was used to identify allelic frequencies for the B and C systems for five consecutive generations of selection (Generations 30 through 34) and three consecutive generations of relaxation (Generations 5 through 7). Haplotypes for the B complex were assigned designations B32, B33, B34, and B55 and alleles of the C system were assigned C8, C9, C1O, and C11'. Production traits for males were BW at 4 and 8 wk of age, and for females were BW at 4,8, and 38 wk of age, age and BW at production of first egg, percentage of normal eggs, and percentage of normal hen-day egg production. There were no differences in production traits among B genotypes or among C genotypes, although some time trends in gene frequencies suggested that more subtle effects may be resent