EFFECT OF ENVIRONMENTAL-TEMPERATURE ON BROILER-CHICKENS SUBJECTED TO GROWTH RESTRICTION AT AN EARLY AGE

An experiment was carried out to evaluate the effect of early growth r estriction (EGR) induced by feed restriction on the ability of male br oiler chickens to withstand exposure to high environmental temperature s. A 2 x 4 factorial arrangement of treatments was employed to determi ne whether such an exposure affects the beneficial effect of EGR on pe rformance and carcass quality. Chicks consumed feed ad libitum or were feed-restricted from 6 to 12 d of age (to achieve 60% growth of the a d libitum birds). From 4 to 8 wk of age, the chickens were kept in tem perature-controlled chambers at 25, 30, 35 C and a diurnal cyclic temp erature of 25:35 C. Weight gain, feed intake, and feed efficiency from 6 to 8 wk of age (after acclimatization to the various temperatures) and BW at 8 wk of age were significantly (P less than or equal to 0.05 ) depressed by the high temperatures (35 and 25:35 C) compared with va lues observed at 25 and 30 C. Early growth restriction did not affect these variables. Relative heart, liver, and breast meat weights at 8 w k of age were decreased significantly with increasing temperature. Rel ative liver weight was also decreased significantly in the EGR chicks, whereas breast yield was increased significantly in these birds. Rela tive abdominal fat pad size was not affected by increasing the tempera ture from 25 to 35 C, but it was significantly lower in chickens kept at 25:35 C than in those kept at 25 and 35 C. Early growth restriction significantly reduced the size of abdominal fat. Because no significa nt interactions between EGR and ambient temperature on the above menti oned variables were observed during 4 to 8 wk of age, it is concluded that EGR can not alleviate the adverse effect of high ambient temperat ure on performance, nor can high ambient temperature obliterate the be neficial effect of EGR in improving feed efficiency and reducing fatte ning.