Estimates of Co-variance Components and Genetic Parameters of Growth Traits in Boran Cattle Breed at Dida Tuyera Ranch, Southern Ethiopia
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Date
2019-01-04
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Addis Ababa University
Abstract
Estimates of Co- Variance Components and Genetic Parameters of Growth Traits in Boran Cattle Breed at Dida Tuyera Ranch, Southern Ethiopia
Genet Zewdie
Addis Ababa University, Jan, 2019
Boran, a popular cattle breed, is predominantly utilized and widely distributed across various countries of Africa. Ethiopia is the origin of this promising breed in terms of milk and beef. In Ethiopia, genetic improvement of the indigenous cattle for dairy production is focusing on cross breeding. It has been practiced for the last five decades, but the success was very low. Therefore, there is a need to develop effective and sustainable genetic improvement schemes for indigenous cattle breeds in Ethiopia. A study was undertaken in Yabello district of Borana Zone with the objectives to estimate the covariance components and genetic parameters of Boran cattle growth traits for Birth Weight (BW),Weaning Weight(WW)and Average Daily Gain (ADG) of Boran calves. The total number of animals considered in this study was one thousand one hundred sixty two (1162), of which number of bulls was six hundred thirty four (634) and number of heifers was five hundred twenty eight (528). The fixed effects or non-genetic factors included in the animal model for the analysis of growth traits were sex, birth year and season. Least square means were estimated using General Linear Model of Statistical Analyses System, SAS. Pedigree was analyzed using Relax 2 program. Variance and covariance components were estimated using AI-REML implemented in the software DMU V.6 package (Madsen and Jensen, 2013). Genetic parameters were using R Studio program. The data records for BW = 1120, WW = 1144 and ADG = 1144 collected between 1991 and 2000. The estimation of the BW, WW and ADG of Boran calves was optimized by evaluating two models that either included or excluded the maternal genetic effects. The best model was chosen according to the log-likelihood ratio tests. Genetic parameters were estimated using R Studio. Sex of the calf significantly influenced BW and ADG (P< 0.01) but not significant for weaning weight. Birth year and calving season significantly (P< 0.001) influenced BW, WW and ADG. The direct heritability estimates to BW, WW and ADG were 0.17, 0.38 and 0.46, respectively. The corresponding maternal heritability estimates were 0.10, 0.17 and 0.15, respectively. The phenotypic correlation between BW and WW was 0.28 while this value was higher than 0.21 between BW and ADG and 0.65 between WW and ADG. The direct and maternal genetic correlation for BW, WW, and ADG were -0.47, -0.45 and -0.47, respectively. The low heritability estimates due to low genetic control because of presence of high environmental influence.
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Boran Cattle, Growth Traits, Heritability, Correlation