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Department of Animal Husbandry, Iowa State College, Ames
ABSTRACT
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 mo., 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 mo. It was concluded that this extra relationship was due to some maternal effect and not to contemporary environment affecting the characters similarly.
1 Journal Paper No. J-3337 of the Iowa Agricultural and Home Economics Experiment Station, Ames, Iowa, Project No. 1053. This research was part of North Central Regional Project NC-2.
2 Present address: Department of Animal Industry, Montana State College, Bozeman, Montana.
3 Present address: Department of Dairy, Michigan State University, East Lansing, Michigan.
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