Utility of an in-line somatic cell count sensor for selecting cows for dry-cow therapy

Area of Science:

• Veterinary diagnostics
• Dairy cattle health
• Antimicrobial stewardship

Background:

• Reducing antimicrobial use in dairy cows requires accurate infection status identification.
• Somatic cell count (SCC) is a common indirect indicator, but in-line sensor utility is unassessed.
• Conventional microbiology is accurate but expensive for routine screening.

Purpose of the Study:

• To determine the diagnostic accuracy (sensitivity and specificity) of an in-line SCC sensor (SenseHub) for identifying intramammary infections (IMI) in dairy cows.
• To compare the utility of the in-line SCC sensor with traditional Dairy Herd Improvement (DHI) SCC data.
• To evaluate the sensor's effectiveness in selecting cows for targeted dry-cow therapy.

Main Methods:

• Prospective diagnostic accuracy study involving 1,544 cows across four New Zealand dairy herds.
• Collection of cow-composite milk samples for conventional microbiology and in-line SCC measurement.
• Analysis of the average in-line SCC over the final 12 weeks of lactation (in-line 12wSCC) as the optimal predictor.

Main Results:

• The in-line 12wSCC showed sensitivity of 0.68 and specificity of 0.71 for any IMI at a cut-point of 150,000 cells/mL.
• For major pathogen IMIs, sensitivity was 0.89 and specificity was 0.51.
• The area under the curve (AUC) for the in-line 12wSCC was non-inferior to maximum and last DHI SCC, indicating comparable predictive ability.

Conclusions:

• The SenseHub in-line SCC sensor demonstrates utility in differentiating infected from uninfected cows for dry-cow therapy decisions.
• Its diagnostic performance is comparable to conventional DHI SCC data, offering a potentially more efficient screening tool.
• This technology supports antimicrobial stewardship by enabling targeted treatment strategies.