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 in
Kg.) and its components such as fat percent (F%), fat yield in Kg (FY), protein percentage (P%), Protein
yield (PY) in kg. and fat/protein ratio (F/P) were analyzed to evaluate the phenotypic performance and
heritability 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 between
the two German Holstein types and among different parities, as well as the interaction between them. It is
clearly seen that the mean values of 4th lactation period for MY, DMY, F%, FY, P %, PY and F/P ratio
were the highest among parities. Data of correlation between milk yield (MY) and its components showed
negative correlation between the milk yield on one side and fat percent, protein percent and fat/ protein
ratio on the other side, while positive correlation is found between milk yield in Kg. , fat and protein yield
in 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 highest
H2 values than those of almost all studied milk traits of both Sbt and Rbt, whereas the H2
values of fat
yield of both Sbt and Rbt are the lowest. It should be noted that H2
values of milk protein percentage are
relatively high.