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 degrees C); diurnal cyclic temperature (temperature was 28 degrees C from 1000 to 1700 h and 22 degrees C from 1700 to 1000 h); and constant high temperature (34 degrees C; temperature was 34 degrees C). In trial 2, broilers from the control and 34 degrees 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 degrees C for 2 h. The 3 cages from the 34 degrees C group were also held in the room at 34 degrees C (34-34 degrees C). Diurnal cyclic temperature had no effect on BW up to 5 wk of age. The effect of 34 degrees C constant temperature on BW of broilers increased with age. Plasma levels of glucose and albumin increased by 34 degrees C, but no dramatic change in levels occurred when those broilers were crated at 34 degrees C. The heterophil:lymphocyte (H:L) was higher for the 34-34 degrees C broilers and the control broilers in the 34 degrees C room than those from the 22 and 15 degrees 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 degrees C and 34-34 degrees 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.

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1. The objective was to evaluate the effects of brooding temperature on intestinal development, oxidative organ damage, and performance of chicks acclimated to high temperature during incubation. The effects of acclimation and brooding temperatures on slaughter weights of broilers under heat stress were also investigated. 2. Eggs were incubated at either 378 degrees C (INC(Cont)) or heat-acclimated at 395 degrees C for 6 h daily from d 10 to d 18 of incubation (INC(H)). Brooding temperatures at floor level were set at 32, 335 and 35 degrees C (Bt(32), Bt(335), Bt(35), respectively) for the first 5 d. The temperature was reduced gradually to 30 degrees C from d 6 to d 10. From 21 to 42 d, broilers from INC(Cont) Bt(32) and INC(H) Bt(32) and Bt(35) were divided into two groups; half from each group was exposed to daily cyclic higher ambient temperatures, while the other half was reared at control temperature. 3. INC(H) chicks had lower jejunum, but greater liver and residual yolk sac weights than INC(Cont) chicks on the day of hatching. Although INC(H) chicks from Bt(335) and Bt(35) had lighter body weights than Bt(32) on d 5, no significant differences were observed in the body weight of broilers among treatments at 10 and 21 d. 4. Similar jejunum protein, alkaline phosphatase, maltase, glutathione, and malondialdehyde contents of chicks from INC(Cont) and INC(H) suggested that heat acclimation during incubation has no effect on jejunum enzyme activity or oxidative status of chicks. 5. Taking into account INC(H) Bt(35) chicks having lower T(3) levels on d 5, lower heterophil/lymphocyte (H/L) ratios and similar weights at 42 d under heat stress compared with control broilers, the results suggested that although higher brooding temperatures had no effect on body weights of INC(H) chicks during the brooding period, those broilers may able to cope better with heat stress.

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The study aimed to investigate the effects of dietary supplementation of oregano essential oil (OEO) on the morphological development of small intestine of broilers with different feeding times (immediate, 24, 48 or 72 h posthatching delayed feeding) from d 0 to 14. The diets were supplemented with: no, 250 or 500 mg/kg of the OEO (OEO250 and OEO500, respectively). Fasting for 72 h significantly increased the weight and length of small intestine segments of broilers on d 14. The OEO250 and OEO500 significantly increased the jejunum villus height of chickens fed immediately and the duodenum villus height of broilers fasted for 48 h. The duodenum villus surface area of chickens fasted for 48 h and the ileum villus surface area of broilers fasted for 24 h were significantly increased by the OEO250. The OEO500 significantly enhanced the duodenum villus surface area of broilers fasted for 24 h and their ileum villus surface area fasted for 48 h. The crypt depths of small intestine segments of broilers fasted for 72 h were significantly reduced by OEO250 and OEO500. In conclusion, the dose of phenolic compounds in OEO reaching the small intestine might be enough for protecting the intestinal epithelial cells from damages of toxins and for removing the negative effects of delayed feeding on the morphological development of all the small intestine segments of broiler chicks on d 14.