Estimation of genetic parameter with actual and reduced records in Holstein dairy cattle in Iran
2004
Ayatollahi-Mehrdjardy, A. | Moradi-Shahrbabak, M. | Nikkhah, A. | Moghimy, A.
In this research, 45800 test day records were collected from 12 dairy herds in Tehran province during 1999 to 2001 by the Iranian Animal Breeding Centre (IABC). Data set included records for milk, fat and protein percentages. Different regression models were applied to estimate daily milk, fat and protein yield on different combinations of milking and sampling times records. Heritability and genetic parameters were estimated using univariate and multivariate animal models with DFREML method based on estimated 305 days records. Results of this research showed that daily and fat yields could be estimated based on night and noon milking times. Heritability of actual and estimated daily milk, fat and protein yield were estimated to be 0.242 and 0.227, 0.174 and 0.174 and 0.157 and 0.141, respectively in repeated record model, while the repeatability of these traits were 0.585 and 0.551, 0.403 and 0.406 and 0.487 and 0.466, respectively. Estimated heritability for adjusted 305-day milk and fat yield and fat percentage records in first lactation were 0.307, 0.204 and 0.338 and for estimate4d recors were 0.301, 0.193 and 0.367, respectively in univariate models. Heritability of mild and fat yield and fat percent were 0.245, 0.176, 0.286 and 0.243, 0.175, 0.361 respectively for adjusted and estimated records in mulltivariate. Rank correlatons between estimated breeding value using actual and estimated daily yield records of milk, fat and protein were 1, 0.928 and 0.949 respectively. Rank correlation between breeding value using actual and estimated 305-d records for milk and fat yield and fat percent were 1, 0.985 and 0.973 respectively.
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