Variability of cow - specific organic matter digestibility within lactation and across cows based on NIRS scans from fecal samples

Near infrared reflectance spectroscopy (NIRS) provides an opportunity to measure cowspecific organic matter digestibility (OMD) from fecal samples. In this study individual digestibility measurements from a trial with 47 cows were investigated. Digestibility increased when lactation progressed. The repeatability estimates between different lactation stages were low which suggests that several fecal collections during lactation are needed to measure cowspecific OMD. Higher repeatability estimates of cowspecific composite samples compared to lower repeatability estimates between individual samples indicate that collecting of composite samples is preferable. The variability of OMD and moderate repeatability estimates give some evidence that genetic improvement of dairy cattle digestibility might be possible, but to make the method practically feasible, further studies on the measurement protocol are still needed.