engleski

Estimation of genetic parameters for milk traits using fixed regression models for Simmental and Black and White cattle in Croatia

The objective of this study was to estimate the genetic parameters for daily milk yield (DMY), milk fat (FC) and protein content (PC) using test-day records of Simmental (SIM) and Black- and-White (BW) cattle in Croatia. Data consisted of 980442 in SIM and 596106 test-day yields in BW cattle. Pedigree included 111909 (SIM), and 74356 BW animals. Variance components were estimated by REML as implemented in the VCE-5 program package. Statistical model included parity, region and calving season as fixed class effects. Calving age was nested within parity as quadratic regression. Days in milk nested within parity was fitted in the model by Ali-Schaeffer lactation curve. Common environment of herd- test-day, direct additive genetic, and permanent environment effects were included in the model as random effects. For SIM cattle, the estimated heritabilities for DMY, FC and PC were 0.45 ± ; 0.01, 0.20 ± ; 0.01 and 0.30 ± ; 0.01, respectively. The corresponding heritability values were 0.32 ± ; 0.002 for DMY, 0.23 ± ; 0.001 for FC, and 0.25 ± ; 0.002 for PC in BW cattle. Permanent enviroment accounted for 3 to 23%, while common environment of herd-test-day effect explained between 11 and 22% of variability.

genetic parameters ; milk trait ; Simmental ; Black and White cattle ; Croatia

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