Selection of dairy cattle for mastitis resistance by somatic milk cells as a system of biological protection against lacteous gland diseases

Abstract

The problems of methodology and organization of selection of dairy cattle for resistance to mastitis by somatic cells of milk were studied. The necessity is justified and the procedure for converting the number of somatic cells (NSC) into a points score (PSNSC) is presented. The article provides evidence of the correspondence of the cows distribution curve by points for NSC to the Gauss curve, which is a sufficient reason to consider the NSC points score as a biometrically correct objective selection trait. Procedures for determining the indices of breeding value of bulls and their breeding categories by somatic cells in points are proposed. Requirements for the level of resistance in the cows and bulls selection are developed. The most resistant to mastitis are cows with a score of 3.9 points or less, and bulls with a breeding value index of -1.012 or less.