This study was carried out through two separate experiments aiming at evaluating the effects of two space allowances (0.54 and 0.62 m2/pig in summer and 0.44 m2/pig and 0.50 m2/pig in winter) on the behavioural and physiological response, and meat quality of pigs of two slaughter weights (120 kg and 140 kg). In summer, higher blood haematocrit levels were found at slaughter in heavier pigs transported at a smaller space allowance (p = 0.04). During lairage, pigs transported at a smaller space allowance started fighting later (p = 0.04). Fighting behaviour was greater in heavier pigs (p ≤ 0.05), whilst their drinking activity was lower (p < 0.05). This resulted in greater exsanguination blood CK levels (p < 0.01) and drier hams (p = 0.05) in heavier pigs. In winter, only lower space allowance influenced some meat quality traits (p < 0.05), but these effects were minor. The effects of space allowance during summer transports on within-truck ambient conditions, post-transport pigs' welfare, and meat quality are similar. Mixing heavier pigs may result in greater aggressiveness and more fatigue-related meat quality variation during summer. Overall, winter transport results may have been biased by the short journey and within-truck load distribution.
Keywords: behaviour; meat quality; pigs; slaughter weight; space allowance; stress; summer; transport; winter.