Some studies have confirmed the variation in milk profiles when dairy cows
show estrus. However, only a few milk components, such as fat, protein, and lactose, have been
investigated so far, and thus any changes in the many other parts of milk’s composition due to estrus
are unknown. Milk mid-infrared (MIR) spectra consist of wavenumbers, which provide insight into
the chemical composition of milk. The MIR spectrum reflects the global composition of milk, but
this information is currently underused. In this study, we considered MIR wavenumbers as traits,
and directly studied the spectral information as a way to study the estrus of dairy cows linked to
milk composition. This research provides a deeper understanding of the milk MIR spectrum and
may lead to new approaches for estrus detection in dairy cows from routine milk analysis, thereby
guiding an opportune insemination time