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Covariance components and genetic parameter estimation for 18 month weight in Nguni and Tuli cattle of Zimbabwe

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Author(s): Never Assan

Journal: Scientific Journal of Agriculture
ISSN 2322-2425

Volume: 2;
Issue: 3;
Start page: 115;
Date: 2013;
Original page

Keywords: Direct | Maternal | Tuli | Nguni | Zimbabwe

ABSTRACT
An animal model wasapplied to estimate variance components and heritability estimates from weightat 18-months (18-mo) pedigree records of two experimental herds of    Nguni and Tuli cattle maintained on rangeat Matopos Research Station. The fixed effects included were of year of birth,sex and age of dam. Random effects were direct and maternal genetic of theanimal and dam with genetic covariance of direct and maternal effects, maternalpermanent environment, and random residual. Estimates of direct heritabilitywere 0.36 ±0.001 and 0.13±0.005 for Nguni and Tuli cattle, respectively. Thematernal heritability was higher for  Tuli cattle, 0.18 as compared to 0.02 for Nguni cattle. Estimates ofmaternal permanent environmental variance as a proportion of phenotypicvariance were less than 1% in both Nguni and Tuli cattle. The direct-maternalgenetic correlations were small and negative for Nguni cattle, and small andpositive for Tuli cattle. Permanent environmental effects were found not to beimportant for 18-mo in both cattle breeds studied. The genetic variance is highin Nguni cattle that response to selection is expected to be high.
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