Comparison of bovine hematology reference intervals from 1957 to 2006

Area of Science:

• Veterinary Medicine
• Hematology
• Animal Science

Background:

• Established bovine hematology reference intervals are from 1965.
• Significant differences were observed between healthy cattle in 2001 and historical data.
• The original 1965 laboratory data allowed for a re-evaluation of changes in cattle hematology over time.

Purpose of the Study:

• To establish current hematology reference intervals for Holstein cows.
• To compare 2001 hematologic results with 1957 data for Holstein cows.
• To compare new reference intervals with those from other North American veterinary institutions.

Main Methods:

• Reference intervals were determined in 2001 from healthy, bovine leukemia virus-negative, mid-lactation Holstein cows.
• Hemograms and neutrophil:lymphocyte (N:L) ratios were compared between 2001 and 1957 data.
• Bovine reference intervals were collected from North American veterinary colleges for analysis.

Main Results:

• Between 1957 and 2001, mean neutrophil counts increased significantly, while lymphocyte, monocyte, eosinophil counts, and hemoglobin concentration decreased.
• The mean neutrophil:lymphocyte (N:L) ratio significantly increased to 1.17.
• Most surveyed labs used the 1965 intervals; newer intervals from two institutions aligned with the 2001 findings.

Conclusions:

• Outdated bovine hematology reference intervals risk misinterpreting neutrophil counts (neutrophilia/neutropenia) and other values.
• The use of N:L ratio >1 as a sole indicator of inflammation should be reconsidered or used cautiously.
• Accurate, current reference intervals are crucial for correct interpretation of bovine hematologic results.