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Turkish Journal of Veterinary & Animal Sciences

Abstract

The lactation cycle is considered one of the most physiologically demanding periods in dairy cows and is accompanied by substantial immunological remodeling. In the present study, spontaneous apoptosis of lymphocytes, monocytes, and neutrophils was evaluated in clinically healthy Ukrainian Black and White dairy cows (n = 28, aged 3–5 years) during different stages of the lactation cycle: colostrum period (3–5 days), mid‑lactation (90–150 days), drying‑off (5–7 days), and dry period (12–20 days). A further group of 28 cows with subclinical mastitis confirmed by the California Mastitis Test was also included in the study. Peripheral blood and milk samples were collected during each lactation stage. Apoptosis was assessed by flow cytometry using dual Annexin V–FITC and propidium iodide staining, while somatic cell count was measured using a fluorooptic method. Statistical analysis revealed that lymphocyte apoptosis increased progressively from the colostrum period to mid‑lactation (p < 0.05) and subsequently stabilized. Monocyte apoptosis peaked during the colostrum period, decreased at mid‑lactation (p < 0.01), and increased again slightly during thedrying‑off and dry periods. Neutrophil apoptosis was highest during colostrum secretion, decreased substantially at mid‑lactation (p < 0.01), and increased again during the drying‑off and dry periods. In cows with subclinical mastitis, somatic cell count was significantly elevated (p < 0.05), and neutrophil apoptosis and the proportion of necrotic neutrophils were markedly increased (p < 0.01). At the systemic level, subclinical mastitis was accompanied by increased apoptosis of neutrophils (p < 0.01), lymphocytes (p < 0.01), and monocytes (p < 0.05) in peripheral blood. It was thus concluded that lactation stage significantly influences spontaneous immune cell apoptosis, with the highest cell turnover observed during the colostrum period and in the drying‑off and dry periods, and that subclinical mastitis exacerbates apoptosis and necrosis processes both locally and systemically.

Author ORCID Identifier

MYKOLA ZHELAVSKYI: 0000-0001-5001-8354

DOI

10.55730/1300-0128.4540

Keywords

Dairy cows, subclinical mastitis, apoptosis, immune homeostasis

First Page

208

Last Page

214

Publisher

The Scientific and Technological Research Council of Türkiye (TÜBİTAK)

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

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