Genetic parameters and correlations among linear type traits in the first lactation of Holstein Dairy cows
The main objective of this study was to estimate the genetic parameters and relationships of 10 linear type traits in the first lactation of Holstein dairy cows. 3274 records for type traits was used (Ag, angularity; Sta, stature; Bdp, body depth; Rw, rump width; Rs, rear leg side view; Fa, foot angle; Fu, fore udder attachment; Ruh, rear udder height; Sl, suspensory ligament and Ud, udder depth) for the first lactation of Iranian Holstein cows collected during 1980 to 2004 at Animal Breeding Center of Iran.
Estimations were performed using restricted maximum likelihood method under an animal model and estimated variance components from single-trait analysis using MATVEC software and covariance components from four-trait analysis using DF-REML software was obtained. Heritability estimates for type traits were low to moderate, from 0.075 for rear leg side (Rs) to 0.376 for rump width (Rw). Genetic correlations between type traits ranged from 0.72 for udder depth (Ud) and fore udder attachment (Fu)
to 0.75 for foot angle (Fa) and rump width (Rw). The results of this study showed favorable and high genetic correlation among the mammary system traits such as Ud, Fu, Ruh and Sl. Body conformation traits such as Ag and Bdp were unfavorable and negative for the genetic correlation with mammary system traits including Fu, Ruh and Ud.
Key words: Genetic parameter, type traits, Iranian Holsteins.