Can Leukocyte Morphology Contribute to Welfare Assessment in Beef Cattle Raised Under Intensive and Extensive Farming Systems?

To investigate the potential contribution of leukocyte morphology to animal welfare assessment, this study evaluated leukocyte profiles in beef cattle raised under intensive and extensive production systems. A total of 664 blood samples were collected at the end of the production cycle from commercial farms in Mato Grosso do Sul, Brazil. Welfare assessments included qualitative behavioral assessment, health indicators, hematocrit, total and differential leukocyte counts, neutrophil-to-lymphocyte (N/L) ratio, and leukocyte morphology using an image-supported scoring system. In pooled descriptive data, severe neutrophil morphological alterations were observed in 27.1% of cattle from intensive systems and 11.4% from extensive systems, while atypical lymphocytes were observed in 21.8% and 9.6%, respectively. Exploratory season-specific generalized estimating equation (GEE) analyses indicated higher neutrophil counts and N/L ratios in cattle from intensive systems in both autumn and spring. In autumn, lymphocyte counts were lower in cattle from the intensive system, and severe neutrophil morphological alterations and atypical lymphocytes had higher estimated probabilities. In spring, no clear evidence of differences between systems was observed for lymphocyte counts or leukocyte morphology. Qualitative behavioral assessment revealed variation among farms, including farms within the same production system. Health alterations, including nasal discharge, coughing, and swelling, were recorded exclusively in the evaluated intensive systems. These findings indicate differences in leukocyte morphology among cattle from the evaluated farms and suggest that leukocyte morphological assessment may provide a useful complementary animal-based indicator within multidimensional welfare assessment frameworks.