Current research is focusing on integrated longitudinal assessment of animal welfare at farm-level. Housing and management systems may influence pain, discomfort, fear, hunger and abnormal behaviour of farm animals. Poor health records and increased levels of haptoglobin have been shown to correlate with an unfavourable environment but, as yet, few data are available regarding variation between individual animals. Hence, a project was carried out using 78 pig farms (farrow-to-finish), 19-20 in each season, with data on housing and management being collected during visits. At slaughter, pathological findings and blood samples were taken from 60 pigs from each farm. Blood samples were analysed for Lawsonia intracellularis (PIA), Mycoplasma hyopneumoniae, salmonella, and haptoglobin values (HAP) (10 samples). Data were analysed with descriptive statistics and analysis of variance. Housing and management characteristics were considered separately and integrated according to Berns (1996). Pigs from higher-ranking farms (ie those scoring higher for housing [space score] and management [sanitary barriers, cleaning, disinfection, climatic control, breeding protocol]) showed lower HAP levels (P < 0.04), with lower within-farm variability (P < 0.06). HAP levels were higher in pigs infected with PIA (P < 0.04) or having lung lesions (P < 0.02). A negative correlation was found between fasting before transport and lung lesions, HAP levels being lower when pigs with lung lesions were fasted. Haptoglobin sampling in the slaughterline is, therefore, relevant for integrative welfare assessment of slaughter pigs at individual level and for longitudinal monitoring at farm level.