Genetic variability of MIR predicted milk technological properties in Walloon dairy cattle

Cheese yield, acidity and coagulation parameters are important technological and economic criteria at the level of farm cheese manufacturing. Since few years, several studies have demonstrated the usefulness of the mid infrared (MIR) spectrometry for the prediction of milk technological properties. Recently, equations for the prediction of Individual Laboratory Cheese Yield (ILCY), acidity and coagulation parameters were developed. The cross-validation coefficients of determination (R2cv) of those calibration equations ranged from 0.65 for rennet coagulation time to 0.81 for dry ILCY. The objective of this study was to estimate the genetic parameters related to the MIR predicted milk technological properties in first-parity Holstein cows from Walloon Region of Belgium. These equations were applied on the spectral database (FUTUROSPECTRE) generated during the Walloon routine milk recording. For each trait separately, records with standardized Mahalanobis distance value higher than 3 or with a predicted value out of the range of the reference values were discarded. After editing, the dataset includes about 100,000 predicted records, depending of the predicted trait, collected on 15,338 Holstein cows between January 2009 and November 2014. The variances components were estimated by REML using single-trait random regression animal test-day model. Random regressions were performed with modified normalized second order Legendre polynomials. The model took into account the heterogeneity of the residual variances over days in milk (DIM). Estimated daily heritabilities are low to moderate, thereby confirming the potential of selection. E.g. they ranged from 0.20 at 5th DIM to 0.49 at 240th DIM for dry ILCY. Further researches will study phenotypic and genetic correlations between predicted technological properties and milk production traits.