title: Broiler chicken thigh and breast muscle responses to cold stress during simulated transport before slaughter.
abstract: 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.
authors.affiliation: Department of Food and Bioproduct Sciences, College of Agriculture and Bioresources, University of Saskatchewan, Saskatoon, Saskatchewan, Canada, S7N 5A8. Samira.dadgar@usask.ca
authors.forename: S
authors.initials: S
authors.lastname: Dadgar
authors.forename: T G
authors.initials: TG
authors.lastname: Crowe
authors.forename: H L
authors.initials: HL
authors.lastname: Classen
authors.forename: J M
authors.initials: JM
authors.lastname: Watts
authors.forename: P J
authors.initials: PJ
authors.lastname: Shand
mesh_terms: D000003:Abattoirs; D000822:Animal Husbandry; D000818:Animals; D002645:Chickens / Q000502:physiology*; D003080:Cold Temperature; D058639:Cold-Shock Response; D008297:Male; D008460:Meat / Q000592:standards*; D008834:Microclimate; D018482:Muscle, Skeletal / Q000502:physiology*; D010369:Pectoralis Muscles / Q000502:physiology; D013848:Thigh / Q000502:physiology; D014186:Transportation