1964 Volume 17 Issue 6 Pages 361-365
The present consideration was made from the results of surveys conducted in the Nayoro district of Hokkaido during a period of four years beginning with 1959.
1. The number of farms raising dairy cattle has been decreasing since 1960. The dairy cattle population has been increasing in the crop field zone of this district, while it has been decreasing in the paddy field zone. Accordingly, there has been little change in the number of dairy cattle kept in this district as a whole.
2. The frequency of occurrence of reproductive disorders has been decreasing very conspicuously in the crop field zone and a little less remarkably in the paddy field zone year after year.
3. The acreage per capita of fields growing feed crops for self-sufficiency has been decreasing in both types of zones year by year. The yield of crops per acre, however, has been increasing as a whole.
4. The higher the rates of self-sufficiency of FU and DTP were in a dairy farm, the lower the frequency of occurrence of reproductive disorders became among the dairy cows kept there. In 1962, the rates of self-sufficiency of FU and DTP and the frequency of occurrence of reproductive disorders were 64.4%, 51.0%, and 16.6%, respectively, in the paddy field zone and 76.6%, 63.0%, and 13.1%, respectively, in the crop field zone.
In conclusion, an increase in reproductivity can be expected from a maintenance of required quantities and, at the same time, an improvement of the quality of self-sufficient feed. It seems particularly important for this purpose to raise the rate of selfsufficiency of DTP.
