Apparent metabolizable energy needs of male and female broilers from 36 to 47 days of age.

Two experiments were conducted to examine AME(n) responses of Ross × Ross 708 male and female broilers from 36 to 47 d of age. In each experiment, 1,440 male and female broilers were randomly distributed into 96 floor pens (15 birds/pen; 8 replicate pens/treatment) sexed separately and were fed 6 levels of AME(n) ranging from 3,140 to 3,240 kcal/kg in increments of 20 kcal of AME(n)/kg, resulting in a 6 × 2 factorial arrangement of treatments. Body weight gain, feed intake, feed conversion, AME(n) intake, AME(n) intake per BW gain, plasma 5-triiodothyronine and thyroxine concentrations, mortality, and meat yields were evaluated during experimentation. Average temperature and RH were 20.3°C and 49.0% for experiment 1 and 26.1°C and 66.6% for experiment 2. In experiment 1, broilers fed progressive additions of AME(n) had lower (P ≤ 0.02) feed intake, feed conversion, and caloric conversion. Progressive increments of AME(n) did not influence plasma 5-triiodothyronine and thyroxine concentrations, carcass yield, or breast meat yield. No AME(n) × sex interactions were observed in experiment 1. In experiment 2, AME(n) × sex linear interactions (P ≤ 0.04) were observed for BW gain, caloric conversion, carcass weight, and total breast weight. Male broilers responded more to higher AME(n) levels than did female broilers. These data indicate that AME(n) needed for growth performance of broilers from 36 to 47 d of age differed between experiments.