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A Simplified Method of Estimating 305-Day Lactation Production^*

Wisconsin Agricultural Experiment Station, Madison, Wisconsin

ABSTRACT

A simplified scheme for computing 305-day milk and butterfat records has been described, and such records have been compared statistically with those estimates calculated by the D.H.I.A. centering method and with actual 305-day milk figures.

The high correlations found between simplified, centered and actual milk records and between simplified and centered butterfat estimates, and the close similarity of their intra-herd repeatability figures and mean yields for milk and butterfat production indicate no important differences between the simplified and centered schemes.

The simplified scheme would offer, however, the following advantages:

1. It would avoid most of the sources of those arithmetical errors which so often occur in the centered calculations.
   
2. It would facilitate the training of testing supervisors.
   
3. It would provide the tester with extra time so that more cows could be tested in one day, or more time could be devoted to conferences with the dairy farmer.
   
4. It would allow the dairy farmer to understand readily the method used in estimating production records, and to make the calculations himself if necessary.
   
5. It would save much time in the recording and checking of production data which are to be used for research purposes.
   

^* Paper No. 328 from the Department of Genetics, Agricultural Experiment Station, University of Wisconsin; published with the approval of the Director of the Station.