Abstract
An experiment was conducted to determine the most appropriate light program and feeding level for the rearing of out-of-season pullets in the tropics and the effects on growth and sexual maturity. Data were obtained during an 18-wk rearing period from 880 Isa Brown medium-sized pullets. The pullets were randomly distributed between two groups subjected to either a constant light program (CLP) or a decreasing light program (DLP) in open houses. In each case, pullets were subdivided into five groups, which received the following feeding programs: control diet (T-1) with a feeding level suggested by the breeding company; 10% (T-2), and 20% (T-3) over the control diet; and 10% (T-4), and 20% (T-5) under the control diet. The variables studied were mean bird weight (MBW), tarsus-metatarsus length (TML), and age at sexual maturity. Under CLP and DLP, respectively, there were no significant differences in MBW among T-1 (1.46 and 1.5 kg), T-2 (1.51 and 1.49 kg), and T-3 (1.47 and 1.56 kg). However, T-4 (1.35 and 1.41 kg) and T-5 (1.26 and 1.29 kg) showed lower MBW (P<0.05). Until 10 wk of age, there were no differences in TML between the two light programs. Under DLP, bone growth at 18 wk was similar for all feed levels: 103,103,104,103, and 101 mm for T-1 through T-5, respectively. However, under CLP, TML of T-5 (101 mm) was less than that of T-1, T-2, and, T-3 (104 mm). Irrespective of light program, overfed pullets demonstrated growth patterns similar to those of the control at 18 wk of age, whereas restriction of feed resulted in less weight than that of control pullets, although bone growth was similar. Feed restriction of 10% (T-4) and 20% (T-5), under both light programs, delayed sexual maturity from three to 14 days compared to that of other treatments.