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"Experientia docet" - Experience is the best teacher

Test-day models for South African dairy cattle for participation in international evaluations

  • 2006
  • Issue: 1
  • Volume: 36
B.E. Mostert, H.E. Theron, F.H.J. Kanfer and E. van Marle-Köster Page: 58 - 70

Variance components and breeding values of production traits and somatic cell score of South African Guernsey, Ayrshire, Holstein and Jersey breeds have been estimated using a multi-lactation repeatability test-day model, including tests of the first three lactations as repeated measures…

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Comparison of breeding values and genetic trends for production traits estimated by a Lactation Model and a Fixed Regression Tes

  • 2006
  • Issue: 2
  • Volume: 36
B.E. Mostert, H.E. Theron, F.H.J. Kanfer and E. van Marle-Köster Page: 71 - 78

A comparison of breeding values and genetic trends of production traits from two models is made. One set of breeding values and trends was estimated by the September/October 2003 South African National Genetic Evaluation, using a Lactation Model (LM). The…

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Adjustment of heterogeneous variances and a calving year effect in test-day models for national genetic evaluation of dairy catt

  • 2006
  • Issue: 3
  • Volume: 36
B.E. Mostert, H.E. Theron, F.H.J. Kanfer and E. van Marle-Köster Page: 165 - 174

South Africa implemented test-day models for genetic evaluations of production traits, using a Fixed Regression Test-Day Model (FRTDM), which assumes equal variances of the response variable at different days in milk, the explanatory variable. Data at the beginning and at…

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Testday models for production traits in dairy cattle

  • 2004
  • Issue: 6
  • Volume: 34
B.E. Mostert, E. Groeneveld and F.H.J. Kanfer Page: 35 - 37

Methodology has been developed to implement testday models in the national genetic evaluation of dairy breeds for production traits in South Africa. Positive definite covariance matrices have been estimated, using multitrait, multi-lactation, fixed regression testday BLUP animal models, including testday…

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Genetic parameter estimates in the South African Jersey breed

  • 1998
  • Issue: 3
  • Volume: 28
J. duToit, J.B. van Wyk and J. van der Westhuizen Page: 146 -

Data obtained from the INTERGIS for Jersey breeders participating in the NationalDairy Cattle Performance and Progeny Testing Scheme were analysed. The registered and grade records commenced in test year 1977 through 1992 (incomplete) and consisting of lactations between 240 and…

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