Selective Value, Quantification and Genetic Parameters of Components of Replacement Traits in Crossbred Cattle

Abstract

A total of 1480 calving records from crossbred cattle maintained at Instructional
Dairy Farm of the University covering a period of 9 years (1994-2002) were used to study
the genetic parameters of replacement rate and its components. The Heritability estimates for
sex ratio, abortion, still birth, mortality, culling, replacement rate on female calf bases and on
total pregnancies bases were observed very low for all the traits. The genetic and phenotypic
correlations among all these traits were observed from medium to very high. Out of total losses
about 71.50% of the cows were died and 28.50% were culled during the entire period of study.
Quantification of different components of replacement rate showed that range of incidence of
prenatal losses was 0.0-17.18 and 0.0-11.69% respectively. In case of male birth, mortality and
culling were ranged from 0.0-100%. Quantification of replacement rate on the bases of female
calves born and on the bases of total pregnancies were observed 0.0-60%. The replacement
index in this study during different periods ranged from 0.90 (1999) to 2.39 (2002). The
replacement index was found more than one during all periods from 1994 to 2002 except 1999
which indicate that the herd size increased during these periods. This showed that the number of
heifers calving compensated the loss of cows from the herd. However, the ratio of the number
of heifers calving to the number of cows lost was found to be little higher than one (i.e. 1.37)
which showed addition in the herd size.