Effects of Temperature During Rearing and Crating on Stress Parameters and Meat Quality of Broilers

Abstract

Two trials were conducted to study the effects of heat stress during rearing (trial 1) and crating (trial 2) on broiler stress parameters and fear, breast meat quality, and nutrient composition. The relationships between stress parameters and meat quality traits were also determined. Trial 1 consisted of 3 temperature treatments from 3 to 7 wk: control (temperature was 22°C); diurnal cyclic temperature (temperature was 28°C from 1000 to 1700 h and 22°C from 1700 to 1000 h); and constant high temperature (34°C; temperature was 34°C). In trial 2, broilers from the control and 34°C groups in trial 1 were used. Broilers in each group were placed in transport cages. The 9 cages from the control group were divided into 3 groups and placed into 3 rooms at 15, 22, or 34°C for 2 h. The 3 cages from the 34°C group were also held in the room at 34°C (34–34°C). Diurnal cyclic temperature had no effect on BW up to 5 wk of age. The effect of 34°C constant temperature on BW of broilers increased with age. Plasma levels of glucose and albumin increased by 34°C, but no dramatic change in levels occurred when those broilers were crated at 34°C. The heterophil:lymphocyte (H:L) was higher for the 34–34°C broilers and the control broilers in the 34°C room than those from the 22 and 15°C room. Breast muscle glycogen level decreased in broilers reared under diurnal cyclic or high temperatures. A lower pH and higher lightness (L*) and redness values and redness:yellowness were found in meat for broilers from both 34°C and 34–34°C groups. Higher H:L was associated with breast muscle pH according to first-order polynomial regression. The H:L had a significant effect on L* values, which were described by a second-order polynomial regression. Blood glucose level was positively correlated with L* and redness values. Duration of tonic immobility was neither influenced by rearing and crating temperatures nor associated with meat quality parameters.