Genetic Relationships between Herd Life and Type Traits of Holstein Cattle in Japan using Random Regression Test-day Models

Abstract Text: The purpose was to investigate the random regression model in estimating changes in the genetic relationships among herd life (HL), milk yield, somatic cell score (SCS), and type traits during lactation. The data included 702,726 test-day records and 20,179 type traits records of Holstein cows in Japan. HL was genetically correlated with SCS, feet and legs, rear udder height, and udder depth. Changes in the genetic correlation between HL and angularity, rump angle, rear udder height, and front teat placement were observed with advancing lactation. These results suggest that the reliability of HL estimates could be increased by using SCS, feet and legs, and udder depth. Rump angle and front teat placement would be useful in increasing the reliability of HL estimates during early lactation, and rear udder height would be useful in doing so during late lactation.

Keywords:

dairy cattle

random regression model

longevity