GENETIC AND NON-GENETIC PARAMETER ESTIMATION FOR PRODUCTIVE AND REPRODUCTIVE PERFORMANCES OF CROSSBRED DAIRY CATTLE AT HOLETTA RESEARCH CENTER

Abstract

This study was initiated to evaluate the productive and reproductive performances of crossbred dairy cattle at Holetta research center dairy farm. Overall, 19,454 crossbred dairy cattle performance records were used for the study. Non-genetic and genetic analysis on the performance of crossbred dairy cattle were applied for estimation. The GLM and regression analysis procedure of SAS 2004 software was employed to determine the fixed and crossbreeding effects of year, season, parity and genetic group (additive, heterosis and recombination effects). On the other hand, WOMBAT, which is a software package for quantitative genetic analyses of continuous traits, fitting a linear, mixed model; estimates of covariance components and the resulting genetic parameters were employed and obtained. From these analyses, the performance of dairy cattle was influenced by genetic and non-genetic factors. Result of fixed effect analysis revealed that year and genetic group were caused significant (p<0.0001) variation in all productive and reproductive traits. Similarly, productive and reproductive traits were also significantly (p<0.0001) influenced by parity except NSC trait. The traits, milk yield, calving interval and days open were sensitive to seasonal variation. The overall least squares means for lactation milk yield, daily milk yield (DMY), lactation length (LL), age at first service, age at first calving, calving interval, days open and number of service per conception were ÷ 2204.05 ± 21.12 kg, 6.88 ± 0.05 kg, 326.69 ± 2.03 days, 26.8 ± 0.34 months, 37.42 ± 0.35 months, 476.35 ± 3.91 days, 197.1 ± 3.88 days and 1.75 ± 0.03, respectively. The highest and lowest heritability estimates from productive traits were 0.28 ± 0.05 for DMY and 0.12 ± 0.04 for LL. The present result indicated that heritability values of reproductive traits were very low (0.012) for NSC to moderate (0.3) for AFC traits. The genetic correlation among productive traits in the present study were positive and low (0.11 between LMY and DMY), slightly high (0.77 between LMY and LL) while negative genetic correlation were observed between AFS and DO (-0.001), AFC and DO (-0.05), AFS and NSC (-0.022), AFC and NSC (-0.29) and CI and NSC (-0.31). Coefficient for the additive effects were much larger than coefficient for heterosis effect for lactation milk yield (2674.05 ± 252.8 kg of additive and 423.9 ± 128.7 kg of heterosis). Crossbreds were 373.9 ± 114.8 days, 337.1 ± 112.6 days, 105.7 ± 54.2 days, 98.5 ± 54.2 days and 0.05 ± 0.4 days reduced AFS, AFC, CI, DO and NSC due to the additive effect of Friesian gene. On the other hand, a reduction of 117.6 ± 61.3 days, 207.9 ± 59.8 days, 4.9 ± 27.6 days and 0.2 ± 0.2 days irrespective of CI were obtained by heterosis retention of the crossbreds. Therefore, from the result of this study, it was possible to concluded that appropriate selection on parental lines and crossing of them to produce calves of the next generation by improving the overall management system in the farm should be implemented for further research.