Comparison between somatic cell and leukocyte variations throughout lactation in camel (Camelus dromedarius) and cow's milk

The relationship between milk somatic cell counts (SCCs), differential leukocytes (macrophage, lymphocyte, and PMNs) and the influence of lactation on these parameters in camel's and cow's milk was compared. Milk was separated into milk with SCC ≤ 105 cells mL−1 (group 1) and milk with SCC ≥ 105 cells mL−1 (group 2). Somatic cell counts and differential leukocytes were significantly correlated in both species and the two SCC groups. In group 1, lymphocytes were the predominant cell type in camel's milk and macrophage in cow's milk. In both species, PMNs were useful indicators to define either uninfected or infected state in group 1 and group 2. In camel's milk, PMN numbers were higher immediately after parturition and declined gradually with advanced lactation, while macrophages number increased through lactation. In cow's milk, PMNs were the dominant cell type at the beginning of the lactation and tended to maintain high levels as lactation progressed. Our results suggest that in some aspects the immune system of camels mammary gland differs from that of bovine.