Transportation welfare under commercial conditions: A multifactorial assessment of stress physiology, meat quality, and microbial load in broiler chickens.

Chickens are often transported for a long distance under overcrowded conditions for human consumption, which affects their welfare, health, and even meat quality. The objective of this study was to investigate the interaction effects of transport distance (60 vs. 80 km), stocking density (0.65, 0.86, and 1.30 ft²/bird), and lairage duration (0 vs. 3 hours) on physiological, haemato-biochemical, microbial, carcass, and meat quality characteristics. A total of 324 broilers was used in a 2 × 3 × 2 factorial arrangement, with truck as the experimental unit, and linear mixed models were employed for data analysis. Higher transportation distance and more space allowance were responsible for more body weight loss during transportation (p < 0.05). Significant distance × density interactions were found for white blood cells (WBC), red blood cells (RBC), hemoglobin (Hb), packed cell volume (PCV), corticosterone, and aspartate aminotransferase (AST) (p < 0.05). Birds transported over 80 km had higher WBC, heterophil to lymphocyte ratio (H: L), lactate dehydrogenase (LDH), and glucose compared to those birds transported over 60 km (p < 0.05). The interactions between distance and lairage on triglyceride and AST indicated partial physiological recovery after 3-hour lairage (p < 0.05). The density-lairage interactions for corticosterone, triglyceride, and RBC were significant (p < 0.05). Prolonged transportation distance increased pathogenic bacterial load (log10 CFU/g) and had a negative effect on meat quality characteristics, including cooking loss of thigh muscle and early postmortem pH of breast muscle (p < 0.05). Overall, extended transportation increased physiological stress and microbes, whereas increased space and lairage reduced many of the adverse effects. The study demonstrated the need to improve transportation techniques to enhance broiler welfare and meat quality.