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Journal of Dairy Science Vol. 35 No. 4 350-355
© 1952 by American Dairy Science Association ®
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A Comparison of Bimonthly and Quarterly Testing with Monthly Testing for Estimating Dairy Cattle Production1

N. D. Bayley, R. M. Liss and J. E. Stallard

University of Wisconsin, Madison

ABSTRACT

Milk and butterfat records for 1,255 Holstein-Friesian cows in 42 herds were computed for the first 305 days of lactation. The centering day method and monthly, bimonthly and quarterly tests were used. The bimonthly and quarterly records were compared to the monthly records according to their variability, average difference in yield, average per cent error and frequency of errors larger than ± 10 per cent.

The results were similar for both milk and butterfat yield. The differences in variability between the monthly, bimonthly and quarterly tests were small. The average differences in yield were significant but unimportant. The average per cent errors from milk yield were 3.0 for the bimonthly records and 5.0 for the quarterly records. The average per cent errors for fat yield were 4.0 and 6.0, respectively, for the two methods. The frequency of errors larger than 10 per cent was one in 46 regarding milk yield in bimonthly records and one in eight in quarterly records. Errors of this size occurred in the butterfat comparisons at the rate of one in 16 bimonthly records, and one in six quarterly records.

The frequency of the large errors indicates that bimonthly and quarterly records should be satisfactory for sire provings and population studies, but they may be unsatisfactory when used as individual lactation records.

FOOTNOTES

1 Published with the approval of the Director of the Wisconsin Agricultural Experiment Station.






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Copyright © 1952 by the American Dairy Science Association ®.