Feasibility of Rapid in vitro Estimation of Haematocrit in Cattle by Using Short-Wavelength near Infrared Spectroscopy

Feasibility of rapid estimation of haematocrit (Ht) in cattle was studied by near infrared (NIR) spectroscopy in the short wavelength (SW, 700–1050 nm) region. The blood samples, held in standard vacuum blood collection tubes, were measured by a custom-designed, portable NIR spectrometer equipped with a Li-ion battery. Sufficient evidence for estimation of Ht was presented by searching the informative wavelength regions and comparing the root mean square errors of prediction (RMSEP) with moving window partial least square regression (MW-PLSR). The result of the MW-PLSR indicated the importance of the water absorption band with a maximum at 970 nm and the absorption band due to deoxy-haemoglobin with a maximum at 760 nm in estimating Ht. Due to light scattering from blood cells, the optical density of the blood does not have a linear relationship to Ht, especially in the low Ht range. In order to improve the prediction accuracy of Ht, an appropriate transformation was proposed for Ht. We confirmed the usefulness of the SW-NIR in estimating Ht, and hope that this technique will replace the time-consuming conventional centrifuge method.