Feeding Regimen, Dietary Vitamin E, and Genotype Influences on Immunological and Production Traits of Broilers

Many functional changes occur during the first 2 wk after a broiler hatches, a period that continues to be an increasing proportion of a broiler's life. Breeding programs are designed to produce a broiler with high potential for growth, yield, and feed efficiency, traits that may compromise health status under husbandry designed to maximize this genetic potential. This experiment compared performances of two broiler lines differing in growth and yield, when reared to 12 days of age under full and diluted feeding regimens containing three dietary levels of vitamin E. Traits measured included body weight (BW), feed efficiency, and allomorphic measures of breast, shank, spleen, bursa, heart, gizzard, ceca, and lung. For bilateral traits, asymmetries were measured. Data were obtained for mortality, response to sheep red blood cell antigen, heterophils, lymphocytes, and response to an E. coli challenge. Responses to dietary feed restrictions and levels of dietary vitamin E during the first 12 days after hatch were noted at market age. There was a trade-off between growth- and health-related traits with responses to husbandry programs, age, sex, and genetic line.