Test-Day Genetic Analysis of Condition Score an Heart Girth in Holstein Friesian Cows

摘要

This study aimed to estimate heritability for condi - tion score and heart girth using a test - day model, to investigate the genetic relationships between condition score, heart girth, and milk yield traits and to analyze the genetic relationships of condition score and heart girth measured at different stages of lactation. Cows from 25 dairy herds were scored for body condition and measured for heart girth at 3-mo intervals for 2 yr. Approximately 5000 test -day observations on condition Score, heart girth, and milk fat and protein yield from 1344 Italian Friesiancows were analyzed using two approaches: 1) repeated observations for a trait were score, heart girth, and milk fat and protein yield from 1344 Italian Friesian cows were analyzed using two approaches: 1) repeated observations for a trait were considered repeated measurements of the same trait; 2) observations for a trait collected in different stages of lactation (dry period, 1 to 75, 76 to 130, 131 to 210, and 211 to 300 DIM) were treated as different traits.