Genetic Parameter Estimation for Casein in Brown Swiss

The most part of Italian Brown Swiss milk goes to cheese so casein is fundamental. The trait currently used in selection is protein content tested in routine milk recording (test-day protein content). Now is possible to determine casein content on each cow by Fourier Transform Infrared Spectroscopy (IR). This allows to analyse casein routinely for each test day. In this study, 1022 milk samples have been collected from 46 herds in 3 Italian provinces, in winter and in summer. Casein percentage for 289 out of the 1022 samples have been analysed also using the reference method for casein (Kjeldahl). The first step was to match the results obtained by IR and by reference method. In order to verify the possibility to employ casein in selection directly, heritability and genetic parameters between traits studied were estimated. The average value for casein percentage tested with IR method was very similar to the one obtained by the reference method (2.72% vs. 2.71%) with correlation of 0.97 Variability coefficients also show limited differences (11.33% vs. 12.12%). Heritability estimated by casein kilogram is 27%, comparable with other productive traits and is therefore possible to obtain a good response to selection.