Date of this Version
For many hundreds of years cattle with the greatest resistance to disease have probably survived to leave more offspring in succeeding generations than those less resistant to disease. Resistance to disease also may have increased indirectly through a favorable association with other characteristics, such as growth rate or milk yield, which have received major emphasis in genetic improvement programs in cattle. However, except for some selection against mastitis in dairy cattle, genetic resistance to disease has not received direct emphasis in genetic improvement programs. Greater understanding of biological mechanisms involved in disease resistance could lead to more effective selection of breeding stock.