The effect of acute cold exposure was assessed on broiler physiology, breast and thigh muscle metabolites, and meat quality. In total, 160 male birds at ages of 5 and 6 wk were exposed to temperatures of -9 to -15°C (cold stressed) and +20°C (control) in a simulated transport chamber for 3 h before slaughter followed by 0 or 2 h of lairage. Bird physiology parameters, including core body temperature, live shrink, blood glucose, and muscle temperature, were assessed. Core body temperature was monitored every minute using i-Button data loggers, and live shrink and blood glucose were assessed. Total glucose and lactate concentrations at 30 h postmortem, as well as ultimate pH (pH(u)), color, and water-holding attributes were evaluated on pectoralis major muscle of breast and iliotibialis muscle of thigh. Birds were grouped based on their microclimate temperature to control and cold-stressed groups (0 to -8, -8 to -11, and -11 to -14°C). Significant (P < 0.05) decreases in core body temperature and breast and thigh muscle temperatures were observed at simulated transport temperatures below 0°C. In addition, higher (P < 0.05) live shrink and lower blood glucose values were observed as a result of 3-h exposure to temperatures below 0°C, exacerbated as temperature decreased further below -8°C. Thigh muscle was almost depleted of glycogen reserve compared with a significant but small reduction in breast muscle glycogen when exposure temperature was below -8°C. Similarly, much greater effects were observed on thigh pH(u) and quality attributes compared with breast. In addition, 84% incidence of the dark, firm, dry quality defect was observed in thigh meat (pH(u) > 6.4, L* < 44) compared with 42% incidence of dark, firm, dry in breast meat (pH(u) > 6.1, L* < 46) when transportation temperature was below 0°C. Results of this study showed that thigh muscle was affected more severely than breast muscle by exposure to cold temperatures before slaughter.
During the winter in Western Canada, broilers are routinely transported in ambient temperatures ranging from 0°C to -40°C, yet there is little research in this area. This study examined the physiology and behavior of broilers undergoing simulated transport at typical Western Canadian winter temperatures. Groups of 15 broilers aged 32 to 33 d were exposed to an air stream regulated to -5, -10, or -15°C. Birds were placed into a typical transport drawer. Following baseline observations, the drawer was placed into a test chamber where cold air was drawn past the birds for 3 h. Three replications were conducted at each temperature. The birds adjusted their position within the drawer based upon the temperature distribution within the drawer. In comparison to the baseline period, exposing the birds to a cold air stream caused them to avoid the front plane (P = 0.003) which was the coldest area within the drawer. The birds did not adjust their usage of the middle (P = 0.308) and rear (P = 0.640) planes, because these were the warmer areas within the drawer. The total amount of space the birds occupied within the drawer did not decrease when exposed to the test chamber (P = 0.669). The core body temperature (CBT) did not vary and was within the known normal range during the normal (P = 0.528), pre-chamber (P = 0.060), and post-chamber (P = 0.285) periods. The CBT of the birds significantly decreased during the in-chamber period (P < 0.001) and then increased during the lairage period (P < 0.001). The shrink loss (P = 0.981) and amount of time to resume feed consumption (P = 0.357) were not affected by exposing the birds to temperatures of -5°C and colder. Exposing birds to temperatures of -5°C and colder had a negative effect on the CBT of the birds. However, the birds demonstrated behaviors which mitigated the negative effect that cold exposure could have on their CBT.
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