Relationship between a fitness-for-transport assessment of broilers before transportation and stress physiology

EU legislation stipulates that unfit broilers may not be transported, but guidelines on how to assess fitness-for-transport are not provided. Moreover, the effect of transport conditions (e.g. crate stocking density; SD) may depend on the broilers’ fitness. We aimed to evaluate a fitness-assessment method and test physiological stress responses to the pre-slaughter phase with different SD. Ross chickens (41d; n=1,939) were transported for 45min at ‘high’ (160cm2/kg), ‘medium’ (190cm2/kg) or ‘low’ (220cm2/kg) SD, and were subjected to a commercially representative pre-slaughter phase duration of ≈16h. Prior to loading, lameness, illness, hock burns, footpad dermatitis, lesions, physical defects, cleanliness and cachexia were scored on a sample of chickens, for categorisation as fit (n=49) or unfit (n=25). Blood was collected before and after the pre-slaughter phase for determination of plasma levels of corticosterone (CORT), lactate, glucose and thiobarbituric-acid-reactive substances (TBARS). Scores for lameness, footpad dermatitis, lesions, illness, defects, and cachexia were, or tended to be, correlated with ≥1 physiological stress indicators. Unfit chickens tended to show or showed lower pre-transport glucose (P=0.077) and lactate levels (P=0.001) than fit chickens, suggesting that the assessment distinguishes between chickens with metabolic differences. Post-lairage, unfit chickens had higher TBARS (P=0.036) and lower lactate levels (P=0.025) compared to fit chickens. At high (P=0.040) and low (P=0.016) SD, plasma CORT levels of unfit chickens were higher than those of fit chickens. Furthermore, plasma CORT levels of unfit chickens increased more at low SD (P=0.010). Generally, high SD resulted in higher glucose levels post-lairage (P=0.002). The association between fitness-for-transport indicators and stress physiology, and the different stress responses depending on fitness, showed that our method potentially identifies chickens that will experience additional stress during the pre-slaughter phase, due to their poor physical condition. High and low SD proved a stressor for all and even more so for unfit chickens.