Genetic Parameters for Conformation Traits of Dairy Cattle in Ningxia
[Objective]Conformation traits have been the focus in dairy cattle breeding,and the selection of conformation traits is crucial for achieving production performance in dairy cattle.This study was conducted to reveal the phenotypic and genetic characteristics of conformation traits,and provide data basis for dairy cattle population in Ningxia.[Method]Conformation linear classification records of 32 532 Holstein cows from 32 farms in Ningxia were collected.The mixed procedure of SAS 9.2 software was used to analyze the influencing factors of conformation traits of dairy cattle in Ningxia.The DMUAI module of DMU software was used to estimate the genetic parameters for conformation traits,including the heritability and the genetic correlations among 20 conformation traits,5 composite traits and final score.[Result]The deviations between the average score and optimal score for conformation traits in dairy cattle of Ningxia ranged from 0.03(udder depth)to 3.73(central ligament),and the average score of 5 composite traits and final score ranged from 80.77(rump)to 87.02(body capacity).The age of first calving,lactation month and parity had significant impacts on 5 composite traits of dairy cattle in Ningxia.The results of unisex animal model estimation showed that the conformation traits of dairy cattle of Ningxia had low to high heritabilities,ranging from 0.04(chest width)to 0.45(stature).The results of doublesex animal model estimation showed that the genetic correlations among traits related with body capacity ranged from 0.04(chest width and loin strength)to 0.72(stature and body capacity score).The genetic correlations among traits related with rump ranged from 0.32(rump width and loin strength)to 0.78(rump angle and rump score).The genetic correlations among traits related with feet and leg ranged from-0.36(heel depth and rear legs rear view)to 0.78(heel depth and feet and leg score).The genetic correlations among traits related with lactation system ranged from-0.13(central ligament and rear udder height)to 0.73(udder depth and fore udder attachment),and the genetic correlations among traits related with dairy character ranged from 0.54(bone consistency and angularity)to 0.96(angularity and dairy character score).[Conclusion]The conformation of dairy cattle in Ningxia performed well,with heritabilities ranging from 0.04 to 0.45 and genetic correlations ranging from-0.36 to 0.96.The genetic correlations among traits in a same body system were found to be medium to high.The results could provide genetic parameters for genetic selection of dairy cattle in Ningxia.
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