Haematopoietic Traits in Indigenous and Modern Pig Breeds Are Modulated by Housing System and Developmental Stage.

Haematological parameters are important indicators of health, physiological status and resilience. In pigs, these parameters are influenced by both exogenous factors, such as feeding, housing and weaning age and intrinsic factors, including physiological maturity and genetic background. In this study, complete blood counts from 512 German Landrace (GL) and German Saddleback (GS) piglets kept in conventional (CON) and organic (ORG) housing systems were analysed throughout four developmental stages until day 70 of life. The GS consistently showed significantly higher counts of red and white blood cells, alongside higher counts of leukocyte subsets such as lymphocytes and monocytes, indicating a potentially efficient immune profile compared to GL. In contrast, GL exhibited larger erythrocytes with higher haemoglobin content as reflected via higher MCV and MCH levels, potentially endowing GL pigs to cope with the high metabolic demands for growth and performance. Housing effects were observed at day 70, where pigs kept in ORG showed reduced HCT and MCV, but higher MCHC levels, which might be attributed to feed components in ORG husbandry, potentially reflecting dietary limitations in methionine. Notably, platelet counts were higher in GL compared to GS piglets under ORG conditions, implying a breed-dependent haematopoietic response. In summary, these findings indicate a trade-off between erythrocyte quantity and haemoglobin-loading capacity, with potential implications for breed-specific myoglobin characteristics. The leukocytes profile further suggests breed-related differences in immune resilience which need to be validated by functional analyses to inform housing and management strategies for weaning in both modern and indigenous pig breeds.