Somatic cell count determination in cow's milk by near-infrared spectroscopy: A new diagnostic tool

The potential of near-infrared spectroscopy (NIR) in the region from 1,100 to 2,500 nm to measure somatic cell count (SCC) content of cow's milk was i nvestigated. A total of 196 milk samples from seven Holstein cows were coll ected for 28, consecutive days, starting from 7th d after calving, and anal yzed for fat, protein, lactose, and SCC. Three of the cows were healthy, an d the remainder had periods of mastitis during the experiment. Near-infrare d transflectance milk spectra were obtained using an InfraAlyzer 500 spectr ophotometer. The calibration for logSCC was performed using partial least s quare (PLS) regression and different spectral data pretreatment. The best a ccuracy of determination was found for an equation that was obtained using smoothed absorbance data and 10 PLS factors. The standard error of calibrat ion was 0.361, the calibration coefficient of multiple correlation was 0.86 8, the standard error of prediction for independent validation set of sampl es was 0.382, the correlation coefficient was 0.854, and the coefficient of variation was 7.63%. The accuracy of logSCC determination by NIR spectrosc opy would allow health screening of cows and differentiation between health y and mastitic milk samples. It has been found that SCC determination by NI R milk spectra is based on the related changes in milk composition. The mos t significant factors that simultaneously influenced milk spectra with the elevation of SCC were alteration of milk proteins and changes in ionic conc entration of milk.