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KMID : 1025520050470020147
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Journal of Animal Science and Technology
2005 Volume.47 No. 2 p.147 ~ p.158
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The Effect of the Incomplete Lactation Records for Genetic Evaluations with Random Regression Test-Day Models (RRTDM) in Holstein Cattle
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Cho Joo-Hyun
Cho Kwang-Hyun
Lee K. J.
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Abstract
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The purpose of this study was to find out the effects that daughters’ incomplete lactation records affect sire’s breeding values through genetic evaluation using RRTDM(random regression test-day model). First, we estimated genetic parameters and breeding values on sires having complete lactation records of daughter by RRTDM, second, we changed complete lactation records of specific sires into incomplete records by various methods. Third, the breeding values were compared between complete and incomplete records. Finally, this study aimed to find out the methods to minimize the estimation errors of young bulls’ breeding values.
Data used in this study were collected from the dairy herd improvement program, and a total of 97,562 records were composed of 10,929 first parity with both parents known, since 1999. Breeding values on the daughters from randomly chosen sires were calculated and compared with among 90day, 150day, and 200day’s incomplete records.
For milk yields, sire’s ranks of breeding values used by complete lactation records were very different from sire’s ranks of breeding values obtained by incomplete lactation records(Rank_90cut, 150cut, 200cut).The differences were also obtained between complete lactation records(per305_full) and incomplete lactation record (per_90cut, 150cut, 200cut) in breeding values regarding persistency. Especially, the differences between per_90cut and per305_full were very large(from 1.8kg to 145kg).
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KEYWORD
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RRTDM, Random-Regression Test-day model, Incomplete Lactation record, Persistency
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