Performance of pureline broiler breeders fed two levels of vitamin E

Reported in this paper is an experiment designed to evaluate responses of t wo commercial broiler dam purelines (A and B) continuously fed 10 or 300 IU of vitamin E/kg from 168 to 441 d of age. Prior to Day 168, all pullets we re fed diets containing 10 IU of vitamin E/kg. During the early laying peri od, percentage hen-day ovulations and percentage hen-day normal egg product ion were similar for both lines and diets. During the latter part of the la ying cycle, there were differences between lines for these traits (A > B), as well as for BW and egg weight for which line differences were reversed ( A < B). Also during this period, percentage hen-day ovulations and percenta ge hen-day normal egg production differed between diets (300 > 10 IU/kg). T hese differences between diets were consistent with the greater number of f emales that entered lay and higher hen-housed egg production of the 300- th an 10-IU/kg group. Although during the laying cycle all females received a fixed amount of feed, BW gains were greater for Line B than A and for the 3 00- than the 10-IU/kg level of vitamin E. Heterophil (H):lymphocyte (L) ratios, percentage livability, and relative a symmetries of shank length and diameter were similar among groups. Pullets from Line B and those fed the higher level of vitamin E exhibited more fear than their counterparts. Head shaking did not differ between vitamin E lev els; however, there was a line-by-time of day interaction for this behavior . The 30-fold difference in dietary vitamin E was reflected by a 15-fold di fference in plasma vitamin E levels in both lines. For vitamin E level in t he yolk, however, there was a line-by-diet interaction. The interaction res ulted from no difference between lines at the 10 IU/kg level and difference s of 10- and 6+-fold in Lines B and A at the 300 IU/kg level, respectively. Overall, responses to continuous feeding of vitamin E at these levels were influenced by genetic stock, age, duration of feeding, and measurement cri teria.