Extending Partial Lactation Milk and Fat Records with a Function of Last-Sample Production

Authors

G. R. Wiggans, Cornell University
L. Dale Van Vleck, University of Nebraska-LincolnFollow

Date of this Version

January 1979

Comments

Published in J Dairy Sci 1979, 62:316-325. Copyright © 1979 The American Dairy Science Association. Used by permission.

Abstract

Holstein production records (364,328) from the Northeast were used to develop a procedure to extend in-progress and terminated records. A function was developed involving last-sample production which accounts for systematic influences in estimating remaining yield, which is yield from day of last sample to day 305. Last-sample production was used because remaining yield is estimated more accurately from last-sample production than from cumulative yield. The function is: estimated 305-day yield = yield in first n days + [(b₁ + b₂n) last production + (b₃ + b₄√n)/last production)] • (305-n). The coefficients (b's) were estimated within three stages (<65, 65 to 245, >245 days in milk), four age at freshening groups (<34, 34 to 48, 49 to 60, and >60 too, 34 to 36 mo cows were placed in the first group if freshening for the first time), three herd yields (<5900, 5900 to 7000, and >7000 kg), and six 2-too season-of-freshening groups by least squares for milk and fat yield. Cumulative yield factors were developed from the same data and compared with this function. The last-sample function had smaller error variance.