Metabolism and Nutrition: Nutrition a -minerals and Vitamins the Vitamin a Requirement for Optimum Growth, Egg Production, and Hatchability in Japanese

wk). Birds grew 819 g during the 4 to 8wk period (CV = 15.0 %), as compared to only 389 g in the 8 to 12 wk period (CV = 15.3 %). Although there was no difference in the variation on a population basis, drastic changes are apparent when data was expressed in relative gains. The variation for relative gains ranged from a low of 17.2 % in the 4 to 8 wk period to a high of 41.0 % in the 16 to 18 wk period. Males which died had a 5 % lower growth trajectory by 4 wk of age as compared to males which survived past 38 wk. The mortality prior to 18 wk was low (total of 2 %). By 38 wk of age, mortality or culling now represented 19.5 % of the 550 males which had been placed. The major causes of death were male kills and septicemia. Growth profi le during rearing may have a role in determining which males will survive in the breeder barn.