Association between days open and milk spectral data in dairy cows

Area of Science:

• Animal Science
• Reproductive Biology
• Spectroscopy

Background:

• Days open (DO) is a critical indicator of reproductive efficiency in dairy cows.
• Accurate prediction of DO can aid in optimizing herd management and improving economic returns.
• Fourier-transform infrared (FTIR) spectroscopy offers a non-invasive method for analyzing milk composition.

Purpose of the Study:

• To associate specific mid-infrared wavenumbers in cow milk with days open (DO).
• To identify the most informative milk sampling periods (days in milk, DIM) for predicting DO.
• To evaluate the influence of systematic effects on the association between milk FTIR spectra and DO.

Main Methods:

• Utilized data from 19,489 Brown Swiss cows in northeastern Italy.
• Analyzed milk samples using FTIR spectroscopy for 1,060 wavenumbers (5,011–925 cm⁻¹).
• Employed linear and Bayesian regression models to associate milk spectral data with DO, considering various DIM intervals (5-90 DIM).

Main Results:

• Specific wavenumber regions associated with fat, protein, urea, acetone, and lactose were linked to DO.
• Milk samples collected during later DIM intervals (31-60 and 61-90 days) exhibited the strongest associations with DO.
• The predictive power of spectral data varied depending on the DIM period and inclusion of systematic effects.

Conclusions:

• Mid-infrared milk spectroscopy can be a valuable tool for predicting days open in dairy cows.
• Optimal milk sampling for DO prediction occurs between 31 and 90 days in milk.
• These findings support the use of FTIR milk analysis for monitoring and improving reproductive performance in dairy herds.