Effect of breed fraction on dairy traits in cattle | Vpliv pasemske sestave na lastnosti mlecnosti pri govedu
2010
Logar, B., Agricultural Institute of Slovenia, Ljubljana (Slovenia).
More than half a million lactation records of cows with known percent of Simmental (SIM) and Holstein (HOL) breeds included in milk recording scheme in the period 1990-2006 were studied. Pure breed was defined as having more than 86 % of genes of the same breed. For the evaluation of breed fraction the linear regression approach of the percent HOL was applied. In a study of SIM, HOL and records of SIM and HOL crossbreds (upSIM) with fixed linear model the lactation yields have increased for 24.8 kg milk, 0.9 kg fat and 0.7 kg protein with every percent of HOL. Records of SIM and of SIM jointed together with upSIM with max 50 % HOL (SIMpop) were evaluated with and without adjustment for the effect of breed fraction using single-trait repeatability animal model. Higher estimates of genetic variances for SIMpop than for SIM resulted in heritabilities from 0.15 to 0.20 for SIMpop and 0.14 to 0.17 for SIM. Without adjustment for the effect of breed fraction breeding values for SIMpop highly increase with the percent of HOL.
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