Impact of pre-slaughter stress on hematological and biochemical parameters in non-ambulatory non-injured pigs

In Brazil, more than 57 million pigs are transported annually to slaughterhouses, and approximately 0.02% (approximately 11,500 pigs) experience severe fatigue, indicating compromised animal welfare. This study assessed the hematological and biochemical parameters in pigs during the pre-slaughter period, comparing animals with non-ambulatory, non-injured (NANI) syndrome with those without the condition upon arrival at the slaughterhouse. Blood samples were collected from 71 pigs (36 NANI and 35 non-NANI) to assess the indicators of stress. Both groups showed mean values for albumin, creatine phosphokinase (CK)-total, CK-MB, cortisol, fibrinogen, and leukocyte, segmented leukocyte, and erythrocyte counts above the established physiological reference ranges. The NANI pigs, however, exhibited significantly higher levels of CK-total (109,573.3 vs. 37,103.33 U/L), cortisol (11.83 vs. 8.94 mcg/dL), and lactate (15.49 vs. 11.85 mg/dL), as well as increased erythrocyte-related parameters (15.23 vs. 13.96 g/dL for hemoglobin; 44.93% vs. 41.96% for hematocrit), lymphocytes (39.5% vs. 31.61%), fibrinogen (677.78 vs. 444.44 mg/dL), and segmented cells (59.96% vs. 46.78%). Conversely, non-NANI pigs showed higher glucose levels (101.22 vs. 79.33 mg/dL). These findings suggest that pre-slaughter handling procedures, including loading, transport, and unloading, induce considerable physiological stress, particularly in pigs affected by NANI syndrome.