Document Type : Research Paper

Authors

• Mahshid Mohammadpanah ¹
• Homayoun Farhangfar ²
• Moslem Bashtani ³

¹ M.Sc., Department of Animal Science, Faculty of Agriculture, University of Birjand, Birjand, Iran

² Professor, Department of Animal Science, Faculty of Agriculture, University of Birjand, Birjand, Iran

³ Associate Professor, Department of Animal Science, Faculty of Agriculture, University of Birjand, Birjand, Iran

Abstract

Correlation between breeding value of crude milk (CM) and energy-corrected milk (ECM) was studied based on a total of 774,013 test day records belongs to 88,456 first-parity Holsteins dairy cattle calving during 1997-2009 in 165 herds (from six provinces). Genetic analysis of the traits was carried out by a fixed regression test day model. In the model, effects of herd, calving year, production month, production age, type of cow genotype (grade or pure Holstein), sperm type, polynomial function, as well as additive genetic and permanent environmental random effects of the cows were included. Mean breeding values as the genetic evaluation is undertaken based on two traits were statistically significant (P<0.0001). Correlation between breeding value of CM and ECM was the highest (0.92) when all the cows were selected based upon breeding value for ECM and was the lowest (0.27) as 10 top cows were selected based upon breeding value for ECM. It could be therefore concluded that in the case of using ECM instead of CM records, change in the ranking of the elite cows is appreciable.

Keywords

• Breeding value
• energy-corrected milk
• Genetic evaluation
• Holstein cow
• test day model

20.1001.1.20096776.1394.17.2.3.7