Phenotypic performance and heritability of milk yield and its component traits of two types of Holstein German cattle.

In the current study, traits of milk yield (total milk yield: MY in Kg. and daily milk yield: DMY inKg.) and its components such as fat percent (F%), fat yield in Kg (FY), protein percentage (P%), Proteinyield (PY) in kg. and fat/protein ratio (F/P) were analyzed to evaluate the phenotypic performance andheritability in five parities of both black Holstein-Schwarzer Bunt Type: Sbt and red Holstein- Bunt Type:Rbt Germany cattle. The milk yield and its component traits showed high significant variation betweenthe two German Holstein types and among different parities, as well as the interaction between them. It isclearly seen that the mean values of 4th lactation period for MY, DMY, F%, FY, P %, PY and F/P ratiowere the highest among parities. Data of correlation between milk yield (MY) and its components showednegative correlation between the milk yield on one side and fat percent, protein percent and fat/ proteinratio on the other side, while positive correlation is found between milk yield in Kg. , fat and protein yieldin Kg., in both Sbt and Rbt types. Data showed that except the milk protein yield in Kg., the heritability(H2) values of all studied milk traits of Sbt are higher than those of Rbt type. Fat% exhibited the highestH2 values than those of almost all studied milk traits of both Sbt and Rbt, whereas the H2values of fatyield of both Sbt and Rbt are the lowest. It should be noted that H2values of milk protein percentage arerelatively high.