<div style="text-align: justify;">This study was aimed to generate information on variance components and the resulting genetic parameters (heritability, repeatability, genetic and phenotypic correlations and genetic trends) of some economic traits of Borena and its crosses with Holstein Friesian dairy cattle maintained at Holetta agricultural research center dairy farm. Traits studied were age at first service (AFS), age at first calving (AFC), calving interval (CI), days open (DO) and number of service per conception (NSC). Overall, 11331 dairy cattle reproductive performance records were used for the study. WOMBAT, which is a software package for quantitative genetic analysis of continuous traits, fitting a linear, mixed model; estimates of covariance components and the resulting genetic parameters were employed and obtained. Heritability values of reproductive traits were from very low (0.071, 0.082 and 0.012) for CI, DO and NSC to moderate (0.3 and 0.22) for AFC and AFS traits. Repeatability estimate for CI, DO and NSC were low (0.17, 0.17 and 0.129). Strong and positive genetic correlation (0.98) was appeared between AFS and AFC traits. Negative genetic correlations 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). AFS were negative phenotypic correlation with CI, DO and NSC. Similarly, AFC was negative phenotypic correlation with CI and DO. Low phenotypic correlation was observed between AFC and NSC, CI and DO, CI and NSC and, DO and NSC. Strong and positive phenotypic correlation was appeared between AFS and AFC. The regression coefficient of mean breeding value for NSC, CI, DO, AFC and AFS on year of birth were -0.0066x+13.25 times/year, -1.19x+2387.4 days/year, -1.23x+2445.6 days/year, 0.2x-410 months/year and 0.48x-980 months/year, respectively.</div>

<div style="text-align: justify;">Analysis of Genetic Parameters for Reproductive Traits in Crossbred Dairy Cattle Maintained at Holetta Agricultural Research Center</div>

<div><strong>Background:</strong> The effect of non-genetic factors including feeding, management, climate, calving year, season and others on animal production improvement has attracted considerable attention in recent years. In addition to improving animal genetics, the importance of optimum environmental conditions in enhancing animal production is recognized.&nbsp;<br />
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<strong>Methods:</strong> Data collected from 2008 to 2018 on 2036 records from crossbreeding dairy cattle herd at Holeta Agricultural Research Center were analyzed to evaluate the genetic and non-genetic environmental effect on lactation milk yield (LMY), lactation length (LL) and calving interval (CI). The fixed effect used in the data analysis were breed group, parity, years group of calving and seasons of calving. GLM procedure of SAS was used to analyze the data.<br />
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<strong>Result:</strong> Results of data analysis indicated that breed group and year group of calving had a significant (P&lt;0.05) effect on LMY, LL and CI. Parity significantly (P&lt;0.05) affected LMY and CI but had no significant effects on LL. While, season of calving had no significant influence on all traits. Least square mean LMY was significantly (p&lt;0.05) highest (3191 kg) for 75% first generation breed group and significantly (P&lt;0.05) lowest for pure Ethiopian Borena breed (124 kg LMY). Mean LL was significantly (p&lt;0.05) highest (354 days) for 75% first generation breed group and significantly (P&lt;0.05) lowest for pure Ethiopian Borena breed (178 days). Least square mean CI was significantly (p&lt;0.05) longest (477 days) for 75% first generation breed group and significantly (P&lt;0.05) shortest (422 days) for 75% <em>inter se</em> mated breed group. Among 75% crosses, the 75% inter se mated breed group had lower LMY (2553 kg) and shorter CI (422 days) compared to 75% first generation breed group. The decline in LMY and CI for 75% <em>inter se </em>mated breed group by 637 kg (25%) and 54 days (13%), respectively compared to 75% first generation, which can be attributed to recombination effect.</div>


<p>Analysis of the Non-genetic Factors Influencing the Performance of High-grade and <em>Inter se</em> Mated Crossbred Dairy Cows at Holetta Dairy Research Farm, Ethiopia</p>


Analysis of Genetic Parameters for Reproductive Traits in Crossbred Dairy Cattle Maintained at Holetta Agricultural Research Center

Analysis of the Non-genetic Factors Influencing the Performance of High-grade and Inter se Mated Crossbred Dairy Cows at Holetta Dairy Research Farm, Ethiopia