Calibration transfer across near infrared spectrometers for measuring hematocrit in the blood of grazing cattle

For fast diagnosis of anemia for cattle farmed on pastures, portable short wavelength near infrared spectrometer instrument was built, and the feasibility of estimating hematocrit by partial least squares regression modeling was validated in our previous work. As a follow-up, the present study reports calibration transfer from one master instrument to two slave instruments. Different approaches, i.e. making robust models, skew and bias correction, and piecewise direct standardization, were compared. Our results show that making more use of simple models based on appropriate preprocessing, number of latent variables, and wavelength selection, can sometimes be as effective as applying standardization algorithm (e.g. piecewise direct standardization) when tackling the spectral differences between instruments. The importance of a robust model during the process of calibration transfer is shown. Application of standardization such as piecewise direct standardization could be risky when the model to be transferred is not robust enough.