| Abstrakt: |
Variance components and genetic parameters are essential tool in animal breeding research and in the design and application of practical breeding programs. Genetic improvement of milk yield and lactation length in dairy cows greatly depends on the phenotypic and genetic variability, heritability and correlation between these traits. The aim of this study was to generate recent information on genetic parameters (heritability, repeatability, genetic and phenotypic correlations and genetic trends) of some economic traits of Borana and its crosses with Holstein Friesian dairy cattle. Overall, 8123 dairy cattle performance records were used for this study. WOMBAT, which is a software package for quantitative genetic analyses of continuous traits, fitting a linear, mixed model; estimates of (co)variance components and the resulting genetic parameters (heritability, repeatability, genetic and phenotypic correlation) were employed and obtained. However, regression analysis was used for estimation of genetic trend by using SAS software. The estimated heritability values for the three production traits were 0.24, 0.28 and 0.12 for lactation milk yield (LMY), daily milk yield (DMY) and lactation length (LL), respectively. Repeatability estimate for LMY and DMY were medium (0.50 and 0.46) but for LL, it was low (0.23). The genetic correlation among milk traits in the present study were positive and low (0.11 between LMY and DMY), moderate between DMY and LL (0.54), and slightly high (0.77 between LMY and LL). However, phenotypic correlation among these traits was very low (0.069 between DMY and LMY), low (0.18 between DMY and LL) and moderately low (0.36 between LMY and LL). Based on genetic trend analysis, the estimated annual gain/change for LMY, DMY and LL were -0.29 liter/year, 0.0015x-2.9 liter/year and 0.038x-74 days/year, respectively. Genetic parameter estimation in the present study had a promising result for milk production traits, which can be further improved by giving particular emphasis for management and continuing to create genetic variability of this herd. [ABSTRACT FROM AUTHOR] |
