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

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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 + [(ba + b2n) last production + (b3 + b4x/-n)/last production)] • (305-n). The coefficients (b's) were estimated within three stages (245 days in milk), four age at freshening groups (60 too, 34 to 36 mo cows were placed in the first group if freshening for the first time), three herd yields (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.

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