GENETIC SELECTION FOR RESISTANCE TO MASTI TIS

This review summarizes the knowledge on genetic control for mastitis d uring lactation in dairy cattle. The usefulness in breeding for resist ance to mastitis of somatic cell counts, type traits, and others indic aters for indirect selection of cattle is discussed. For the selection to be rapid and effective, it is necessary to define not only the eff ects of environment, infectious agents and host on the occurrence of m astitis but also the breeding objective. Is it necessary to select the animals completely resistant to intramammary infectious (complete eli mination of the pathogens) or to select asymptomatic carriers? Do we w ant to select cows resistant at the entry of pathogens into the mammar y gland or resistant to the establishment of the pathogen inside the m ammary gland? Do we want to breed cows resistant to all pathogens or r esistant to one specific pathogenic type? In conclusion, the suggested scenario is to select cows needing the least sanitary procedures when subject to the mammary pathogens present in their environment without decreasing their productivity.