The Studies on The Development of 305-day Adjustment Factors and Formulas for Production Traits in Dairy Cattle
2009
Cho, K.H., National Institute of Animal Science, RDA, Cheonan, Republic of Korea | Lee, J.H., National Institute of Animal Science, RDA, Cheonan, Republic of Korea | Na, S.H., National Institute of Animal Science, RDA, Cheonan, Republic of Korea | Son, S.K., National Institute of Animal Science, RDA, Cheonan, Republic of Korea | Seo, K.S., National Institute of Animal Science, RDA, Cheonan, Republic of Korea | Kim, S.D., National Institute of Animal Science, RDA, Cheonan, Republic of Korea | Choi, J.G., National Institute of Animal Science, RDA, Cheonan, Republic of Korea
This study was performed to make it possible to adjust milk production records which are changing with days in milk more accurately as developing new 305-day adjustment factors considering current circumstance and to offer easier application by converting adjustment factors to formulas. Total 4,264,347 records were used in this analysis after eliminating unusual value and data was classified by first parity and over second parity. Herd-year effects were classified with 2,878 and 19,783 classes in first parity and over second parity, respectively and number of subclass of age-calving season-lactation stage effects were 136 (age 2, calving season 4, lactation stage 17). For calculation of least square mean, SAS GLM was used and multiplicative adjustment factors were developed. The result of error analysis, deviations between means of adjusted yields and cumulated yields were the lowest in new adjustment factor which was developed in this study comparing with other adjustment factors which were developed in the past (94', 02') in first parity and in over second parity, results of adjustment factors which were developed in 2002 and this study were similar. For easier application, formulas of 305-day adjustment factors were developed using SAS NLIN.
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