Genetic background of claw disorders in the course of lactation and their relationships with type traits.

Random regression threshold animal models were applied to binary longitudinal claw disorder data for studying genetic parameters of all claw disorders ( ACD), as well as to claw disorders divided into different categories: non-purulent claw disorders ( NPCD), purulent claw disorders ( PCD), dermatitis digitalis ( DD), sole ulcer ( SU), phlegmona ( PH), laminitis ( LAM) and interdigital hyperplasia ( IH) in the course of lactation. Claw disorder data were obtained from 26 651 Holstein cows kept in 15 large-scale contract herds in the region of Thuringia over a period of 5 years from 2007 to 2012. If a cow had one or more entries of the same disorder, for example, sole ulcer, within an interval of 30 days, she was scored with a '1', and otherwise, she received a score of '0' for healthy. Heritabilities for the same disorder were relatively stable between DIM 50 and DIM 300, but they tended to increase in early and late lactation. Highest heritabilities in the range from 0.20 to 0.34 were estimated for IH, and lowest heritabilities were realized for LAM (~ 0.05). Genetic correlations for same traits between different DIMs were high for adjacent test days, but close to zero for distant test days. The relationship between the sire EBVs for claw disorders and official sire EBVs for the type traits 'foot angle' was slightly antagonistic with correlation coefficients in the range from 0.05 ( DD) to 0.33 ( PH). Correlations between lactation EBVs for hock quality, rear leg rear view and the feet and leg index with EBVs for claw disorders were slightly favourable and ranged between −0.01 (rear leg rear view correlated with SU) and −0.43 (hock quality correlated with PH). Regarding daily EBVs for claw disorders, the strongest correlation coefficient was of value −0.46 ( LAM early in lactation correlated with the feet and leg index). Genetic parameters from the random regression model were verified by applying a single-trait repeatability model. Correlation coefficients between lactation EBVs from the random regression model and lactation EBVs from the repeatability model for the same claw disorder were close to 1. Correlations were lower between EBVs from single test days and lactation EBVs from the repeatability models, with a minimal value of 0.58 for PCD measured at day 20. [ABSTRACT FROM AUTHOR]