Estimation of genetic parameters and maternal effects of Brangus cattle using BLUP /
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1991.
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| Subjects: | |
| Online Access: | Link to OAKTrust copy |
| Abstract: | Data from 16,066 purebred Brangus cattle were analyzed for components of genetic variance using mixed linear model methodology. The characters analyzed were birth weight (BW), weaning weight (WW) and postweaning daily gain (ADG) on test (male calves only; N = 5,000). A maternal effects animal model (MATEFF) was fit to the data with age (2 yr, 3 yr, 4 yr and over 4 yr) and breed (Brangus, Brahman and Brahman-crosses, Brahman x British, Holstein and Undefined) of maternal dam, contemporary group and cytoplasmic breed of origin (Angus, Brahman and Unknown) included as fixed effects. Age of calf at weaning was grouped into 5 d intervals and included in weaning weight analyses. Additive genetic direct and maternal (co)variances were estimated by pseudo expectation. A second model (NONADD) was fit to a subset of the ADG data which included additive, dominance and additive x additive genetic effects and contemporary groups as a fixed effect with variance components estimated by tilde-hat. Analyses were also conducted with a subset containing 9,470 records for BW and WW and 2,746 records for ADG, where maternal breedtype was Brangus (BRNG SET). Data for NONADD comprised embryo transfer calves whose surrogate dams were Holstein (N = 1,749). Maternal heritabilities for BW (.13 and .13) were greater than heritabilities for direct effects (.09 and .10 for FULL SET and BRNG SET, respectively) and genetic covariances were near zero (.05 and -.08). Maternal heritabilities for WW (.37 and .28) were larger than for direct (.18 and .12 for BRNG SET and FULL SET, respectively) effects, and the genetic covariance was -.25 and -.45 for FULL SET and BRNG SET. Direct effects for ADG were more important than maternal effects, with estimated heritabilities for direct effects of .41 and .43 for BRNG SET and FULL SET and both estimates of heritability for maternal effects less than .05; estimated genetic covariances were approximately .20. Younger dams gave birth to and weaned lighter calves than older dams... |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Genetics." |
| Physical Description: | ix, 96 leaves ; 29 cm |
| Bibliography: | Includes bibliographical references. |