Response to divergent selection for early growth of chickens fed a diet deficient in selenium

Three generations of divergent selection for 21-day growth response to a diet deficient in selenium (-Se) were bred using a meat-type chicken. The Athens-Canadian Randombred (AC) population of chickens served as the base population for this study. Mass selection was used to establish a -Se refractory line (SDR) and a -Se susceptible line (SDS). A genetic control line was maintained during the selection process to facilitate evaluation of the responses of the selected lines. The SDR males and females had an average of 17% increase in weight gain at 21 days of age when fed the -Se diet compared with the control line males and females fed the same diet for the three generations of selection. The SDS line had an average reduction in weight gain of 27% during the same period of selection. A difference of 25 g was observed between the mean body weights of SDR males and females and between the SDS males and females after one generation of selection. By the third generation of selection, the difference between SDR and SDS males had increased to 31 g, whereas the SDR and SDS females differed by 41 g. Early response to selection was asymmetrical because the response was greater in the SDS than in the SDR line. Response to selection, however, generally declined after the first generation. Realized heritability estimates for individual generations for this trait were variable (ranging from -.26 to .95), but cumulative estimates (.15 to .39) for growth through three generations were similar to those reported for chickens and quail.(ABSTRACT TRUNCATED AT 250 WORDS)