Relationships between Body Measurements, Meat Conformation, and Milk Production

Some aspects of growth, conformation, and milk production, and their interrelations were investigated. The data were milk production and various measures of size at birth, 6 too., 1 yr., and 2 yr. of age in the Iowa State College Holstein herd. Negative genetic associations between milk production and all measures of size except wither height were found. These associations indicate that any effort to select for milk production alone would lead to animals with reduced chest girth relative to wither height, chest depth, body length, and weight. Accordingly, any effort to select both for milk production and for a conformation indicating good production of meat would require considerable compromise in both. The correlations between dam's production and daughter's size were consistently larger than the reciprocal correlations between dam's size and daughter's production. This excess was not evident at birth but was as strong at 2 yr. as it was at 6 too. It was concluded that this extra relationship was due to some maternal effect and not to contemporary environment affecting the characters similarly.