FORMATION OF SELECTION TRAITS FOR IMPROVE D RESISTANCE TO MASTITIS

Various direct selection traits were tested for improved udder health through breeding on the basis of evidence from a commercial dairy with a high concentration of animals. The traits differ according to the m anner of the findings (clinical and bacteriological), in the duration of the diseases under consideration, and in the duration of the testin g period, which includes one or more or partial lactations. Clinical s ecretion findings displayed the higher estimated heritability values o f h2 = 0,04 to 0, 1 7, compared with bacteriological findings of h2 = 0,01 to 0,06. A trait which includes all diseases in the testing perio d is hardly advantageous to the breeder when compared with an alternat ive trait which allows only the difference between healthy and disease d, An extension of the testing period effects an increase in the herit ability of the clinical findings. The estimated values of the bacterio logical findings, however, remain uninfluenced by the duration of the testing period. Of all variants tested, clinical findings prove to be the alternative trait in the first lactation which, as most favourable selection trait, is recommended for future testing.