Effect of Test Day Milk Yield in Early Lactation on Incidences of Claw Disorders

Production level affects incidence of disease and vice versa. Relationships between four different claw disorders (dermatitis digitalis, sole ulcer, wall disorders, interdigital hyperplasia) and test day milk yield were analyzed in a Bayesian framework allowing recursive models to data from 5360 Holstein cows. A two-way causal path was postulated describing first the influence of test day milk yield on claw disorders and, secondly, the effect of the disorder on milk yield at the following test day. Posterior means of genetic correlations between level of milk yield at individual test days and disorders ranged between 0.16 and 0.43 suggesting that breeding strategies focussing on increased milk yield increase susceptibility to claw disorders. Structural coefficients in the model described recursiveness at the phenotypic level. The increase of disease probability per 1 kg increase of test day milk yield ...