ESTIMATION OF GENETIC AND NON-GENETIC PARAMETERS FOR PRODUCTIVE AND REPRODUCTIVE TRAITS OF CROS- BRED DAIRY CATTLE AT HOLETA AND DEBER ZEITE AGRICULTURAL RESEARCH CENTERES, ETHIOPIA

Abstract

The comparative estimation of genetic and non-genetic parameters of productive and reproductive traits of local and cross-bred dairy cattle conducted at Holeta and Debre Zeit Agricultural research Centers based on long-time recorded data generated for the last 46 and 33 consecutive years was used for this study. The average lactation milk yields of dairy cattle in both research centers were 14 24.32 ± 41.56 for local, 2334.08 ± 28.63 for 50%, 2354.08 ± 28.63 for 50% -75% and 2108.32 ± 41.56 (L) for >75%. The mean average of lactation milk yield (LMY) for all cross bred was 2265.49±32.94 (L) whereas the average LMY for locals was 1424.32 ± 41.56 (L). Lactation milk yields of cross-bred dairy cows with different exotic blood level in both research centeres were highly significant (P < 0.001). Genotype, calving years, location of the centers, calving season and parity were significant (P < 0.05). The average lactation length (LL) of dairy cattle in both research centeres were 204.43 ± 2.60 for local, 285.06 ± 2.32 for 50%, 282.5 ± 2.32 for 50-75%, and 273.04 ± 2.19 days for >75%, and the mean average lactation length (LL) was 280.2±2.28 days for cross bred and 204.43± 2.60 days for locals. Cross-bred dairy cows with different exotic blood level (local, 50%, 50% -75%, and >75%) in both research centres were highly significant (P < 0.001). The average calving interval(CI) of dairy cattle in both research centers was 478.31 ± 7.69 for local, 472.85 ± 5.88b for 50%, 482.75 ± 5.85 for 50% -75%, and 503.56 ± 5.77 days for >75% with the mean average calving interval of 486.39±5.83 days for crossbred dairy cattle. Calving interval (CI) of cross-bred dairy cows with different exotic blood levels (local, 50%, 50-75% and >75%) in both research centres were highly significant (P < 0.001). Age at first calving (AFC) were 1171.62+39.40, 1103.49+ 29.42, and 1184.28+29.56 days for local, 50%, 50-75% and >75%), respectively with a coefficient of variation 17.31% in both research centres. AFC is not significant (P>0.05) between the two research centers. The average days open and number of services per conception of dairy cattle in both research centres were 268±58.9 and 2.18±45.9 for locals, 195±35.7 and1.45±35.6 for 50%, 185±43.3 and 1.25±55.4 for 50%-75%, and 165±38.7 and 1.22±45.4 for>75%, respectively. The variance of analyzed factors such as centres, calving year andcalving season were not significant (P>0.05) in number of services per conception. Location of the centres and calving year were significant (P < 0.05) in number of days open. Parity and calving season were not significant (P>0.05) in number of days open. Parity wassignificant (P<0.01) in number of services per conception while genotype was highly significant (P<0.001) in days openand number of services per conception. Direct heritability xviranged from 0.043 in calving interval to 0.393 in age at first calving for the dairy herd maintained at Holeta agricultural research center. The phenotypic correlation among the pairs of traits investigated ranged from 0.022 in lactation length and age at first calving to0.931 in total milk yield and lactation length. The repeatability values for the traits analyzed ranged from 0.133 in calving interval to 0.244 in total milk yield for the dairy herd maintained at Debre Zeit Agricultural Research Center. In general, the increasing and decreasing genetic trends over the observed year and seasons show that making the right decision for the right selection of breeds and culling unproductive breed which leads to dairy cattle production and reproductive performance improvement through good farm management conditions in the right environmental conditions.