The Combined Impact of Lairage Temperatures and Controlled Atmosphere Gas Stunning time on Meat Quality and Blood Metabolites

Abstract

Lairage, a holding area where poultry are kept prior to slaughter and controlled atmosphere stunning (CAS) are two factors associated with poultry processing that can influence both the physiological state of a bird, and the quality of the meat produced. Despite this, the possible impacts of both lairage temperatures and CAS together are widely unexplored. Understanding the potential effects is imperative to improving processing plant efficiency, enhancing meat quality, and optimizing processing conditions. For this study, the effect of lairage temperature and CAS on broiler breast meat quality and blood metabolites was investigated. A 2x2 experimental design was used to evaluate two simulated lairage environments (hot: 28.9°C and cool: 17.3°C) and two stunning durations (4.5 and 6 minutes). Broilers were exposed to the simulated lairage conditions for 1 hour. Blood samples were taken pre-lairage, post-lairage pre-stun, and post-stun. Using an iSTAT Alinity v, 13 blood metabolites were evaluated: PCO2 (mmHg), pH, PO2 (mmHg), HCO3 - (mEq/L), SO2 (%), TCO2 (mEq/L), Na (mEq/L), iCa (mmol/L), glucose (mg/dL), hematocrit (%PVC), and hemoglobin (g/dL). Following lairage birds were stunned using CAS and processed normally. After immersion chilling and deboning, breast fillets were evaluated at 2 and 24 h for pH, color, and drip loss. At 24 h and 7 d lipid oxidation readings were taken. At 2 h postmortem, birds stunned for 4.5 min had higher pH than those stunned for 6 min (P = 0.027), and at 24 h, birds from the cooler lairage environment had higher pH than those from the hot environment (P < 0.0001). Fillets from hot lairage birds were lighter and more yellow at both 2 h and 24 h postmortem compared to cool birds (P =0.0008). No differences were observed for drip loss or lipid oxidation. CAS time significantly affected blood gases (HCO₃⁻, pH, PCO₂, SO₂), electrolytes (Na, iCa), and glucose (P < 0.0001), with a glucose and hemoglobin interaction observed between lairage temperature 2 and CAS time (P = 0.034, P = 0.046). Hematocrit was higher in the 4.5-minute stunned birds (P = 0.008). This work aims to investigate how different lairage temperatures and CAS can influence broiler meat quality and blood chemistry, ultimately providing valuable insights for improving poultry processing practices.