ESTIMATION OF GENETIC PARAMETERS AND NON-GENETIC FACTORS FOR BIRTH WEIGHT AND REPRODUCTION TRAITS OF PURE JERSEY DAIRY CATTLE AT ADEA BERGA RESEARCH STATION

Abstract

This study was conducted to estimate non-genetic factors and genetic parameters for birth weight and reproduction traits of pure Jersey dairy cattle at Adea Berga Research Station. A total of 11,794 pure Jersey dairy cattle performance records which were collected from 1986 to 2019 was used for the study. The General Linear Model (GLM) procedures of SAS software were used to determine the effects of non-genetic factors. Genetic parameters and variance components were estimated by Average Information Restricted Maximum Likelihood (AIREML) algorithm using WOMBAT software fitting animal models. The results indicated that the the overall least square means (± SE) of age at first service (AFS), age at first calving (AFC), days open (DO), calving interval (CI), number of service per conception (NSC) and birth weight (BW) were 22.88 ± 0.20 months, 32.68 ± 0.1 9 months, 205.53 ± 4.48 days, 479.80 ± 4.45 day, 2.01 ± 0.02 and 22.3 ± 0.09kgs, respectively. Year of birth had highly significant (P<0.001) effect on AFS, AFC and BW. Similarly, Season of birth had highly significant (P<0.001) effect on AFS and AFC. Parity of dam had significance effect (at least p<0.05) on all traits of BW, CI, DO and NSC. Year of calving had highly significant (p<0.001) effect on CI and DO. Cow weight at calving had significant (p<0.01) effect on CI, DO and calves BW. Year and season of service had highly significant(<0.001) effect on NSC. The estimated heritability values of reproductive traits were 0.48 ± 0.04, 0.06 ± 0.03, 0.21 ± 0.07 and 0.03 ± 0.02 for AFC, CI, cow weight at calving (CW) and NSC respectively. Additive and maternal heritability of BW were 0.25 ± 0.08 and 0.1 ± 0.07 respectively. Repeatability value for CI, NSC and CW were 0.12 ± 0.04, 0.09 ± 0.02 and 0.28 ± 0.06 respectively. The genetic correlations among reproductive traits were varied from 0.10 to 0.92. The Phenotypic correlations among reproductive traits were varied from -0.02 to 0.50. The moderate heritability estimate observed for AFC and BW indicated that genetic improvement for these traits might be possible through selection. Therefore, from the result of this study, it can be concluded that, AFC and BW performances of pure Jersey cattle at Adea Berg research dairy xiv farm were promising for further improvement through selection of parental lines to produce better calves of the next generation. However, the higher estimates of DO, CI and NSC indicated the need of improving the farm management system