Abstract
This experiment was conducted to estimate the SNP effects for milk production traits by parity using a total of 506,481 test records from 293,855 heads of Holstein cows calved from 2002 to 2016 and the information on 41,837 SNPs from 2,007 heads. Most of the SNP effects for milk yield were distributed from –1 to +1 and most of the SNP effects for fat yield and protein yield were in the range of –0.04 ~ +0.04 and –0.03 ~ +0.03, respectively. For milk yields, the numbers of SNPs whose effects were more than 4 standard deviations in the first, second and third parity were 9, 11 and 11, respectively and the number of common SNPs whose effects were more than 4 standard deviations in all parity was 5. For fat yields, they were 14, 9 and 8, respectively in the first, second and third parity and the number of common SNPs whose effects were more than 4 standard deviations in all parity was 8. For protein yields, they were 9, 7 and 6, respectively in the first, second and third parity and the number of common SNPs whose effects were more than 4 standard deviations in all parity was 2. There was no common SNP with more than 4 standard deviations for milk, fat and protein yields. This might be due to the genetic composition differences among milk production traits.
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