Effect of the pre-slaughter logistic chain on some indicators of welfare in lambs

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The present study analyzed the effects of the pre-slaughter logistic chain on some indicators of welfare and meat quality in commercial light lambs at two different seasons. A total of 144 male lambs of the Rasa Aragonesa breed were sampled in a 3 × 2 factorial design, testing three different stay times at a classification centre (CC). The CC had a central barn for weight classification with a curved race system and scale. Lambs at (or at times over) the correct commercial weight were kept in holding pens in the central barn. Lambs below commercial weight were sent to fattening pens in two large lateral barns (with 50 pens of approximately 18 m2 each for about 40). The groups were classified as G0 (only a few hours at the CC), G7 (7 days of fattening at the CC) and G28 (28 days of fattening at the CC). Two replicates were performed per treatment and two replicates were carried out in the different seasons (summer and winter). The approximate age and weights of the lambs were 100 days and 28.3 ± 0.25 kg (G0), 93 days and 25.5 ± 0.25 kg (G7), 72 days and 17.3 ± 0.25 kg (G28). The physiological stress response variables measured were cortisol, lactate, glucose, creatinine kinase (CK), non-esterified fatty acid (NEFA), white blood cells (WBC), red blood cells (RBC), haematocrit and ratio of neutrophil:lymphocytes (N/L). The ultimate pH on Longissimus dorsi (pH24) and bruising score of the carcass were assessed. Stay time and season had a significant effect on stress variables. Cortisol and lactate levels were highest for G28 (p < 0.01) while haematocrit was highest for G0 (p < 0.05). The G0 and G7 lambs had higher levels of glucose than G28 (p < 0.05). The highest WBC count was observed for G28 (p < 0.001). In winter, cortisol and glucose levels were higher, while in summer CK was highest (p ≤ 0.001). In summer, N/L was significantly higher in G28 (p ≤ 0.001). Cold temperatures had a significant effect on pH24 and bruising score (p ≤ 0.001). The results of our study suggest that the pre-slaughter logistic chain was a source of stress for the lambs, affecting their physiological state, even under optimal commercial conditions. This effect may represent the cumulative effects of all factors associated with the classification centre.