Cytologic features of bone marrow in normal and mastitic cows

Area of Science:

• Veterinary Medicine
• Hematology
• Immunology

Background:

• Mastitis is a significant economic and animal welfare concern in dairy cattle.
• Understanding the bone marrow's response to infection is crucial for managing inflammatory conditions.

Purpose of the Study:

• To investigate the impact of mastitis on bovine rib bone marrow cell counts and myeloid/erythroid ratios.
• To assess changes in neutrophil reserves and granulopoiesis during experimentally induced and naturally acquired mastitis.

Main Methods:

• Aspiration of rib bone marrow from normal and mastitic cows.
• Nucleated cell counts and differentiation of 500 cells in marrow films.
• Induction of mastitis via Streptococcus agalactiae and Escherichia coli endotoxin.

Main Results:

• Myeloid/erythroid ratio was <1.0 in normal cows and >1.0 in mastitic cows.
• Mature neutrophil reserves were depleted in mastitis, with neutropenia and left shift in blood.
• Immature granulocytes increased in marrow, followed by intensified granulopoiesis.

Conclusions:

• Bovine mastitis severely impacts neutrophil reserves, leading to depletion and peripheral neutropenia.
• The bone marrow demonstrates a robust regenerative response (granulopoiesis) to restore neutrophil homeostasis.
• These findings highlight the dynamic hematological changes occurring during bovine mastitis.