This experiment was conducted to investigate the effect of duration of feed withdrawal and full-feeding during high environmental temperature condition on broiler chicken performance and mortality rate. One hundred and twenty one-day old brown Shaver broilers were used in this study. The experiment consisted of four groups, each group included three replicates of 10 chicks each. The broilers were full-fed ad libitum in the control group 1 (FFC) while feeders were removed for three (at 9.00 a.m. and return it at 12.00 p.m.), six (at 9.00 a.m. and return it at 3.00 p.m.) or nine (at 9.00 a.m. and return it at 6.00 p.m.) hours per day in groups 2, 3 and 4, (FW3, FW6, and FW9) respectively from 2 to 7 weeks of age. The average indoor temperature was 26-38 °C. The obtained results could be summarized as follows:
No significant differences in the final body weight, feed consumption and cumulative feed conversion ratio were observed between full-fed and all restricted broilers. The broilers of all restricted-fed groups had fewer deaths than that of the control group. The mortality rate was 13.3, 10.0, 0.0 and 10.0% for groups 1, 2, 3, and 4, respectively.
No significant differences in carcass weight, its percentage, as well as the percentage of femurs, breast, wings, blood, feet & shank, heart, liver, gizzard, giblets, intestine, drumsticks & femurs fat, and total fat weight were found among all groups. However, significant (P≤0.05) differences were detected in the percentage of head, back, skin, proventriculus, spleen, gallbladder, abdominal fat, subcutaneous fat and breast fat of the groups. The broilers of all restricted-fed groups had significantly lower (P≤0.05) percentage of drumsticks & femurs as compared with that of FFC. It could be observed that, the FFC group had significantly higher (P≤0.05) neck fat as compared with all restricted groups, while it had significantly lower (P≤0.05) heart fat. The FW6 birds had insignificantly lower total fat than that of FFC birds. All restricted fed broilers (groups 2, 3 and 4) increased economical efficiency by 13, 99 and 2%, respectively as compared with FFC broilers. The FW6 group had the best economic efficiency (EE) value.
It could be concluded that, the most suitable feeding regime during high environmental temperature is the withdrawal of feed for 6 hours per day at 9.00 a.m. and return it at 3.00 p.m. from 2 to 7 weeks of age because it was best economically efficient than other feed restriction regimes. Also, using this regime was associated with a reduction in fat deposition and with no mortalities.