Gebeyehu Goshu
Data collected from at Holeta Bull Dam Station from 118 sires and 902 dams were used to asses distribution of threshold traits as affected by sire variance and calving traits cows. The traits studied were type of birth (normal, abnormal), sex ratio, and female calves reached to age at first calving. Variance analyses were made to estimate effect of sire variances and repeatability of cows on the above threshold traits. The result showed that from the total of 1223 female births, 67.7% reached to productive age. Sire affected type of birth (P<0.05), sex ratio (P<0.01), and female calves reaching to productive age (P<0.0001). The distribution of calf production traits of cows showed that 30.8% of cows calved only once, 27.7% calved abnormal births at least once in their life time and 27.3% left the herd without producing any female progeny. The probability of a cow repeating abnormal birth, given the previous birth was abnormal, was very high (0.96). It is commendable to test semen for genetic disorder other than milk yield trait to expand dairy production in the country. The number of female calves reaching to productive age can be increased through introduction of sound reproductive management and improving survivability of calves.
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