Genetic analysis of disease treatments in an organised performance test

In the present study disease treatments from three dairy farms with an total overall herd size of 3200 cows were analysed. Data recording took place between Febuary 1998 and December 2002. Within lactation data recording ended after 50, 100, or 300 days of lactation. Lactation animal models and test day animal models were used for the analyses. These models were used as threshold models and linear models. The diagnoses of the veterinarians were allocated to a disease categorie. Available disease categories were udder diseases (39934 treatments), fertility diseases (24563 treatments), metabolic diseases (4131 treatments), and claw and leg diseases (5085 treatments). For the different disease categories the disease frequencies ranged from 12.6 % to 50.4 %. If lactation threshold models were used the estimated heritabilities for udder diseases were between 0.07 and 0.08, whereas the heritabilities vary between 0.12 and 0.17 when test day threshold models were used for the analyses. The heritability of liability to mastitis, estimated with a linear model was 0.01. The genetic correlation between mastitis and SCS was 0.84. Further the genetic correlation between mastitis and milk production traits ranged from 0.20 to 0.34. The genetic correlations between the different disease categories estimated with a multivariate linear model were in the interval between –0.18 to 0.82 and the heritabilities for the different disease categories ranged from 0.02 to 0.03.

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