Factors Affecting Replacement Rate and its Components 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 components of replacement rate. The sex ratio (% male birth) was found to be 51.49%. The chi square test indicated that the deviation in sex ratio from the normal expected ratio was significant. The differences in frequency of male birth due to sire, season and period of calving were non significant. The incidence of abortion was observed to be 7.77% and the frequency was significantly affected by season and period of calving, while sires have non significant effect. The still birth, was found to be 4.73%, and their frequency were affected by sire and season of calving, while non significantly affected by period of calving. Mortality and culling rate were found to be 45.60% and 18.18% respectively. The effect of season, period and sire were highly significant on mortality rate, while on culling season effect was significant. Percentage of calf reaching to milking herd were found to be 26.62% and 36.49% based on the basis of total pregnancies and on the female calf born basis. The effect of season was recorded significant on the replacement rate on both the basis, while sire causing significant effect only on the replacement rate on the basis of total calf born. The effect of period was recorded non significant in both the cases. Out of total losses about 71.50 per cent of the cows died and 28.50 per cent were culled during the entire period of study. 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.