Physiological responses of Manchega suckling lambs: Effect of stunning with different CO2 concentrations and exposure times

Four groups of Manchega breed suckling lambs, stunned with different CO2 concentrations and exposure times (G1: 80% CO2 90 s; G2: 90% CO2 90 s; G3: 90% CO2 60 s; G4: 80% CO2 60 s) plus an electrically stunned control group (G5), were used to determine (1) the physiological responses (hormonal, haematological and biochemical blood parameters) of animals after stunning and (2) the stunning effectiveness in each group. No significant differences were found among groups for hormonal levels. Within haematological parameters, significant differences among groups were only found for haemoglobin (P < 0.05) and leucocytes (P < 0.01), with lowest values in both groups stunned with 90% CO2. There were significant differences between groups (P < 0.01) for urea and total protein, creatinine and LDH (P < 0.05; lowest and highest, respectively, for G1) and for sodium (P < 0.001; lowest in G3). Stunning effectiveness was highest in G5, G3 and G1 groups and lowest in G2 and G4 (100%, 90%, 89%, 50% and 43%, respectively). According to discriminant analysis, sodium, leucocytes and creatinine marked the differences among stunning groups.