Estimation of backfat thickness using extracted traits from an automatic 3D optical system in lactating Holstein-Friesian cows

Data recording was performed on the dairy research farm Karkendamm of the Institute of Animal Breeding and Husbandry of the University of Kiel (Germany) from July 2011 to May 2012. BFT measures (n=2931) and two measures (n=1779 and n=1848) obtained from Time-of-Flight recordings from 96 primiparous and multiparous Holstein-Friesian dairy cows were analyzed using seven different linear (mixed) models. BFT estimation using the cow as random or fixed effect, lactation week and observation month as fixed effects, and a linear regression on the two Time-of-Flight measurements has been promising. The correlation among observed values and estimator was 0.96. Repeatability of BFT within each of the three lactation stages was large and ranged from 0.80 to 0.89. Correlations of cow effects among lactation stages were also high and range from 0.65 between first and third lactation stage to 0.89 between second and third lactation stage.