Data secured in an investigation which has now been under way for eight years at the Iowa Agricultural Experiment station give direct support to the belief that a good paying dairy herd can be built up from a foundation of common cows thru proper methods of feeding and management and thru the use of a good purebred dairy sire. The results of this work are presented in a preliminary way in this bulletin and will be given in more complete form when the investigation has been carried further.

Investigations of this kind are fundamental to the task of increasing dairy production to meet increasing demands for dairy products because they seek to find ways of getting more milk and butterfat from the overwhelming majority of common cows. There are in the United States, according to government reports, more than 20,000,000 so-called dairy animals whose average production is not half as much as it might be if proper methods of selection, breeding, feeding and management were followed by all dairy farmers. Any information that will help to build up better and more productive dairy herds from these animals is consequently of large value.