Van Wyk, J. B.Erasmus, G. J.Fair, Michael Denis2017-03-222017-03-222002-11http://hdl.handle.net/11660/5951English: Genetic parameter estimates were compared usmg Gibbs sampling and REML methods. Variance components and resulting heritabilities of birth weight (BW) and weaning weight (WW) in the Elsenburg Dormer sheep stud were estimated using a conventional (REML) and a Bayesian (GIBBS sampling) approach. A sire model with relationships included were fitted in both cases. Data from 10701 lambs recorded from 1943 to 1999 were used in the analyses. Effects fitted as fixed were sex (male, female); birth status (single; twin, triplet); year (1943-1999) and age of dam (two to seven years, and older). Sire and residual were the only random effects fitted. The posterior means (h2) ofBW and WW were 0.24 and 0.15 for REML and 0.23 and 0.16 for the Bayesian method respectively. The heritability estimates obtained were of the same magnitude and in accordance with estimates found in the literature where sire models were used. Genetic parameters for the pre-wearung growth traits BW and WW were also calculated from the (eo )variance components estimated using the ASREML program by fitting univariate animal models. Log likelihood ratio tests were done to determine the appropriate mixed models. Bivariate models were also fitted for BW and WW using as starting values for the (eo)variance components the values obtained from the univariate analysis. Fixed effects fitted were the same as in the previous section. The direct heritability (h2 a) for BW and WW for the bivariate model was 0.22 and 0.12 respectively. The maternal effects (m2 ) were 0.24 and 0.11 for BW and WW respectively. These m2 values fall within the range 0.09 to 0.31 found in literature. The direct-maternal genetic correlations (ram) of -0.38 and -0.38 for BW and WW were similar to those found in literature. Genetic parameter estimates for reproduction traits, i.e. number of lambs born (NLB), number of lambs born alive (NLBA), number of lambs weaned (NL W), total weight weaned (TWW) and survival traits were obtained using the ASREML program fitting univariate animal models. Data for TWW were pre-corrected for fixed and random effects of sex, year and sire respectively. An animal model with only the direct random effect of animal and fixed effects of birth status and birth year of the ewe was fitted. Direct heritability (h2a) estimates of 0.12, 0.14 and 0.10 were obtained for TWW1, TWW2 and TWW3 respectively. Direct heritability (h2 a) and (SE) estimates of0.103 (0.016),0.101 (0.016) and 0.031 (0.011) were obtained for NLB, NLBA and NLW respectively. Permanent maternal environmental variance components as proportions of phenotypic variance for the three traits were 0.013 (0.005), 0.008 (0.009) and 0.023 (0.008) respectively, with service sire variance as a proportion of phenotypic variance of 0.005 (0.004), 0.007(0.004) and 0.006 (0.003) respectively for the traits mentioned. Heritability estimates for direct and maternal effect of survival were 0.03 (0.018) and 0.00 (0.00). Permanent maternal environmental variance as a proportion of phenotypic variance for survival was 0.077 (0.017). It was concluded that Gibbs sampling could be of use to the animal breeder while the question of negative covariances between direct and maternal genetic effects still need further investigation. TWW could be used as selection criteria for reproductive efficiency.Afrikaans: Beramings van genetiese parameters IS deur van Gibbs-monstering en REMLmetodes te gebruik, vergelyk. Variansie-komponente en gevolglike oorerflikhede van geboortegewig (Ggew) en speengewig (Sgew) is in die Elsenburg-Dormerskaapstoet deur 'n konvensionele (REML) en 'n Bayes (GIBBS-monstering)-benadering beraam. 'n Vaarmodel met ingeslote verwantskappe is in beide gevalle gepas. Data van 10701 lammers, wat vanaf 1943 tot 1999 aangeteken is, is in die ontledings gebruik. Effekte wat as vas gepas is, was: geslag (manlik, vroulik); geboortestatus ( enkel, tweeling, drieling); jaar (1943-1999) en ouderdom van moeder ( twee tot sewe jaar, en ouer). Vaar en fout was die enigste toevallige effekte wat gepas is. Die posterior gemiddeldes (h2) van Ggew en Sgew was onderskeidelik 0.240 en 0.153 vir REML en 0.234 en 0.161 vir die Bayes-metode. Die oorerflikheidsberamings wat verkry is, was van dieselfde omvang en in ooreenstemming met beramings in die literatuur waar vaarmodelle gebruik is. Genetiese parameters vir die voorspeense groei-eienskappe Ggew en Sgew is ook bereken vanaf die (ko)variansie-komponente, beraam deur ASREML-deur die passing van 'n enkelveranderlike dieremodel. Log-aannneemlike verhoudingstoetse is gebruik om die geskikte gemengde modelle te bepaal. Dubbelveranderlike modelle is ook vir Ggew en Sgew gepas, deur die waardes wat van af die enkelveranderlike ontledding verkry is, as beginwaardes vir die (ko)variansie-komponente te gebruik. Vaste effekte wat gepas is, was dieselfde as in die vorige afdeling. Die direkte oorerflikheid (h2 a) vir Ggew en Sgew vir die dubbelveranderlike model was onderskeidelik 0.22 en 0.12. Die maternale oorerflikhede (m2) was onderskeidelik 0.24 en 0.11 vir Ggew en Sgew. Hierdie m2-w.aardes val binne die omvang van 0.09 - 0.31 wat in die literatuur gevind word. Direk-maternale genetiese korrelasie (ram) van -0.38 en -0.38 vir Ggew en Sgew onderskeidelik was dieselfde as dié wat in die literatuur gevind is. Genetiese parameterberamings vir vrugbaarheidseienskappe, i.e. aantal lammers gebore (ALG), aantal lammers lewendig gebore (ALLG), aantal lammers gespeen (ALS) en totale gewig gespeen (TGS); en oorlewings- (OORL) eienskappe is verkry deur die ASREML-program te gebruik waarin enkelveranderlike eienskappe gepas is. Data vir TOS was vooraf gekorrigeer vir die vaste en toevallige effekte van geslag, jaar en vaar onderskeidelik. 'n Dieremodel met slegs die direkte toevallige effek van dier, en vaste effekte van geboortestatus en geboortejaar van die ooi is gepas. Direkte oorerflikheid (h2 a) en SF-beramings van 0.12 (0.05), 0.l4 (0.05) en 0.10 (0.05) is onderskeidelik vir TgewS1, TgewS2 en TgewS3 verkry .. Direkte oorerflikheid (h2 a) en SF-beramings van 0.l03 (0.016), 0.l01 (0.016) en 0.031 (0.011) is onderskeidelik vir ALG, ALLG en ALS verkry. Permanente maternale omgewingsvariansie as 'n proporsie van fenotipiese variansie vir die drie eienskappe was 0.0l3 (0.005), 0.008 (0.009) en 0.023 (0.008) onderskeidelik, met diensvaar-variansie as 'n proporsie van die fenotipiese variansie van onderskeidelik 0.005 (0.004), 0.007 (0.004) en 0.006 ( 0.003) vir genoemde eienskappe .. Oorerflikheidsberamings vir direkte en maternale effek van OORL was 0.03 (0.018) en 0.00 (0.00). Permanente maternale omgewingsvariansie as 'n proporsie van fenotipiese variansie vir OORL was 0.077 (0.017). Gibbs-monstering kan van nut wees vir die diereteler. Negatiewe ko-variansies tussen direkte en maternale effekte benodig verdere ondersoek. TGS kan as 'n seleksie kriteria vir reproduksiedoeltreffendheid gebruik word.enDormer (Sheep) -- Breeding -- South Africa -- ElsenburgDormer (Sheep) -- South Africa -- Elsenburg -- GeneticsDissertation (M.Sc.Agric. (Animal, Wildlife and Grassland Sciences))--University of the Free State, 2002DissertationUniversity of the Free State