Estimates of genetic parameters for lactation traits in Taiwan Holsteins
Date Issued
2006
Date
2006
Author(s)
Chen, Jih-Yih
DOI
zh-TW
Abstract
The objectives of this study were to estimate genetic parameters, including heritabilities and correlations, of milk yield, milk components and somatic cell score traits with field data of Holsteins in Taiwan, All these genetic parameter estimates of important economic traits would be expected to be used in the genetic evaluation of dairy cows in the future.
Dairy production data were retrieved through SQL server using open database connectivity (ODBC) from the Dairy Herd Improvement (DHI) database in Taiwan, and original 109,944 records from Holstein cows with first calving from April 1989 to November 2003 were included which were from to 580 herds and 1,752 sires, respectively. These original retrieved data were edited with dBASE III PLUS and used to request summary statistics by SAS package firstly, and the genetic parameters of milk yield, somatic cell score and milk components for the first three lactations were estimated with VCE5 software. The data set included files of trait records (27,916, 18,758 and 9,257 cows for first, second and third lactation, respectively), county-year-season fixed factor (361, 358, and 339 levels for each lactation, respectively), and pedigree of 4 generations of ancestors.
The genetic parameters of lactation were estimated with Restricted Maximum Likelihood using animal model. Model included fixed county-year-season effects, random animal and error. Estimated heritabilities for the first three lactations included 305d milk yield (MY), fat yield (FY), protein yield (PY) and log somatic cell score (LSCS) were 0.34 ± 0.02, 0.37 ± 0.02, 0.38 ± 0.02, and 0.16 ± 0.01 for first lactation, 0.22 ± 0.02, 0.21 ± 0.02, 0.24 ± 0.02, and 0.09 ± 0.01 for second lactation, and 0.24 ± 0.03, 0.28 ± 0.03, 0.31 ± 0.03 and 0.12 ± 0.03 for third parity respectively. Those heritability estimates were moderate for production traits and lower for log somatic cell score trait which was in agreement with the literature. Heritability estimates of the first lactation for all traits were higher than the later lactations been estimated, and the decreasing of heritability estimates for later lactations may be caused by increasing environmental variance. Genetic correlation estimates across lactations for the three milk yield traits were positive and ranged from 0.82 to 0.99, implying that selection for milk yield will appear genetic improvement for fat yield and protein yield traits. There were almost negative genetic correlations estimates between production and log somatic cell score traits (ranged from –0.40 to 0.13), however, LSCS was not show disadvantageous effect if only milk yield was selected.
Subjects
泌乳性狀
遺傳參數
Taiwan Holsteins
lactation traits
genetic parameters
Type
thesis