School of Agriculture, Food and Ecosystem Sciences - Theses

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Start date: 1968 × Subject: Breeding × Subject: Cattle × Subject: Victoria ×

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    Genetic improvement in beef cattle : and developing breeding programs for Dookie Agricultural College and for Turkey
    Koc, Atakan ( 1996)
    This thesis analyzed performance records for Polled Hereford beef cattle collected over 34 years from Dookie Agricultural College. It uses two sources of information for size traits for the animals: accumulated raw data and BREEDPLAN's Estimated Breeding Values (EBVs). Comparisons were made between the two sets of data. As expected growth rate and size traits are differed between sexes, males were the highest, females were the smallest and steers were in between. Phenotypic correlations among size traits were moderate to high. EBV traits showed very high `genetic' correlations among size traits, but negative genetic correlations with 200-d. Wt Milk EBV. Sires' own EBVs were highly correlated with progeny group mean EBVs. The relationship with progeny adjusted phenotypic means were lower. Heritability values for phenotypic adjusted weights were for sire progeny groups; for Birth Weight (BtWt) female 0.30, male 0.38, for 200-d Wt female 0.42 and male 0.47, and for 400-d Wt female 0.28 and male 0.19; and for dam progeny groups, for BtWt, female 0.78, male 0.59, for 200-d Wt females 1.48 and male 1.66, for 400-d Wt female 1.06 and male 0.32. These values indicate that dams exert a non-genetic maternal effect particularly for 200-d Wt. Although the heritabilities for EBV traits were expected to be 1.00, (estimated from the `genetic' differences between the animals), except for BtWt and 200-d Wt Growth EBV for females, this study's estimates were much higher than 1.00. This suggests that the process of estimating breeding values has been unreliable for evaluating the animals of this herd for 200-d Milk, 200-d Wt Growth for males, 400-d and 600-d growth. The analysis results and supporting literature were used to develop breeding programs for Dookie and for Turkey. Areas of further research are suggested in the. conclusion.