Genetic Analysis of Several Disease Categories Using Test Day Threshold Models in German Holstein Cows

Abstract. In the present study trajectories for the disease categories udder diseases, metabolic diseases, all diseases, fertility diseases, and ovarian problems, are described. Variance components were estimated where the considered period of lactation varies between 50 and 300 days. Furthermore, the impact of the number of daughters per sire was analysed with disease information from the first 50 days of lactation. In total 18 data sets were analysed with a test day threshold model. The average disease frequencies were between 6.5% and 2.7% for udder diseases and they were between 1.7% and 0.4%, and 15.3% and 6.0% for metabolic diseases and 'all diseases', respectively. For udder diseases the estimated heritabilities vary between 0.12 and 0.25 depending on lactation length and the number of daughters per sire. For metabolic disease heritabilities were estimated within the interval of 0.12 to 0.24. Depending on the lactation length the heritabilities of all diseases were fairly constant (0.03 to 0.04). The heritabilities of all diseases increased if fertility diseases were excluded. Those estimates vary between 0.15 to 0.19.