Investigations of the importance for breeding of maternal lines in a Saxonian dairy cattle population - 1st communication: Results of the estimation of variance components

The simple population genetic model is not sufficient to explain difference s in milk performance traits between maternal lines. These differences are caused by extrachromosomal (i.e. cytoplasmic inheritance) and maternal gene tic effects. The goal of our studies is to discriminate these effects in a dairy cattle population in Saxony (Germany). To address this issue, varianc e components of milk performance traits were estimated using the REML 3.2 s oftware package. Data was collected from 58,857 cows, which were separately analyzed according to their origin (six farms). Results: Effects between m aternal lines of all subpopulations were only observed for the protein cont ent. Small effects between maternal lines were found for all milk performan ce traits when subpopulations were analyzed separately. Based on these resu lts, we hypothesize that extrachromosomal inheritance influences mainly the protein synthesis and to a lower degree the fat content of the milk. The m aternal-genetic variance of the entire population exhibited significant est imation values. Variance components are the foundation for the estimation o f the breeding values, which are shown in our second communication.