Apoptosis and necrosis of polymorphonuclear leukocytes in goat milk with high and low somatic cell counts

The purpose of the present trial was to compare the percentages of necrotic and apoptotic polymorphonuclear leukocytes (PMNL) in goat milk with low and high somatic cell count (SCC). Twenty eight milk samples were collected from 20 lactating goats, determined to be negative in bacteriological examination, and divided in three groups, according to their SCC: samples with SCC lower than 500 × 10³ cells/mL; between 500 and 1500 × 10³ cells/mL; and higher than 1500 × 10³ cells/mL. SCC was performed in an automatic somatic cell counter. Apoptosis and necrosis were quantified using dual-color flow cytometry with fluorescein labeled annexin-V and propidium iodide (PI). Results of the present study showed a significant positive correlation between the percentage of the viable PMNL and milk SCC (r = 0.495, P = 0.008), as well as a significant negative correlation between apoptotic PMNL and milk SCC (r = −0.486, P = 0.009). Results also pointed out lower PMNL viability rates due to higher apoptosis rates in milk samples with SCC lower than 5 × 10⁵ cells/mL.