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KMID : 1025520130550030173
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Journal of Animal Science and Technology
2013 Volume.55 No. 3 p.173 ~ p.178
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A Consideration on the Lactation Persistency Evaluation in Korean Holstein Dairy Cattle
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Cho Kwang-Hyun
Yoon Ho-Baek
Cho Chung-Il
Min Hong-Ryp
Lee Jun-Ho
Kong Hong-Sik
Lee Hak-Kyo
Park Keong-Do
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Abstract
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The characteristics of lactation persistency was investigated for new evaluation trait using 4,366,900 milk yield records from 436,690 heads of Korean Holstein dairy cattle. The average lactation persistencies of first parity, second parity and over third parity were 97.5%, 95.1% and 94.6%, respectively and there was a trend that after the peak yield, lactation persistency decreased collectively. The average days of peak milk yields after calving was about 50 days, but only 33.2% of cows reached peak yields at 36~66 days (second test day). Also, there was a difference between the milk yield of cows which reached peak yields at first test day by lactation days and that of cows which reached peak yields at second to fourth test day. The estimates of heritabilty and repeatability for mean lactation persistency were 0.16 and 0.35, respectively. The genetic correlation between cumulative lactation persistency from third to tenth test day and that from third to seventh test day was 0.91 and while it increased in later test day, it decreased sharply in earlier test day. The breeding value correlations of Data II and III for Data I were 0.80 and 0.72, respectively, while the rank correlations were 0.78 and 0.71, respectively. Based on the results, the breeding value and rank correlations decreased when more data were added.
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KEYWORD
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Genetic correlation, Heritability, Holstein, Lactation persistency
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