[The relationship between udder health and milk production in SMR cows]

Analyses made of seven dairy units revealed that clinically manifest udder inflammations had occurred once or repeatedly to 23.9 per cent of all cows in their first lactation and to 34.0 percent during the fourth lactation. Cows with no clinical udder inflammation in the first and second lactations were superior by 205 kg of milk to animals in whom such inflammations developed during the second lactation. Correlation coefficients between udder health and milk yield were between -0.22 and 0.32 and were likely to suggest that in the long run improvement of the genetic potential for milk yield was accompanied by deterioration of udder health. Therefore, udder health should be included by stabilising selection in Friesian dairy cattle breeding in the GDR. A sufficient breeding potential will be left for milk yield parameters, as was shown by simulated selection experiments.