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"Experientia docet" - Experience is the best teacher

Genetic improvement of sow longevity and its economic impact on commercial pork production

  • 2019
  • Issue: 6
  • Volume: 49
B.E. Mote, T.V. Serenius, C. Supakorn, & K.J. Stalder Page: 1036 - 1046

Sow longevity (sow productive lifetime) plays an important role in economically efficient piglet production. Direct selection for sow longevity is not commonly practiced in any pig-breeding program. In recent years, an increased number of peer reviewed articles addressing the economic…

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Index-in-retrospect and breeding objectives characterizing genetic improvement programmes for South African Nguni cattle

  • 2014
  • Issue: 2
  • Volume: 44
L.E. Matjuda, M.D. MacNeil, A. Maiwashe, V.R. Leesburg & M. Malatje Page: 161 - 172

The goals of this research were to document the historical selection applied by Nguni breeders that contributed to the national genetic evaluation scheme, and to offer prospective breeding objectives to guide future selection practices. Genetic selection differentials, weighted by number…

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’n Seleksiestelsel vir Angorabokke

  • 1981
  • Issue: 1
  • Volume: 11
D.G. Poggenpoel & J.M. van der Westhuysen Page: 35 - 48

The effect of different production traits on the income of Angora goat farming was investigated. From the few estimates available in the literature, it was concluded that the heritability of production traits of the Angora is of the order of…

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Two-way selection for egg albumen quality

  • 1982
  • Issue: 3
  • Volume: 12
D.G. Poggenpoel Page: 389 - 391

Two White Leghorn lines were selected for increased and decreased Haugh units. After 6 generations there was a significant difference of 17,1 Haugh units between lines, but response in the high line was 4,5 times more than in the low…

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Vooruitgang op die gebied van reproduksie-fisiologie

  • 1985
  • Issue: 3
  • Volume: 15
C.H. van Niekerk Page: 102 - 108

Advances in reproductive physiology. Reproductive physiology plays an important role in the genetic improvement and increasing the fertility of the cow. The following factors which have an important influence on increasing the fertility of the female animal are discussed: Selection…

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Genetic progress in the poultry industry

  • 1986
  • Issue: 3
  • Volume: 16
R.M. Gous Page: 127 - 133

In this article progress attributable to genetic selection in the poultry industry is discussed in three sections: genetic progress in broilers and broiler breeders, in laying hens, and in disease resistance. Selection methods are evaluated and future objectives are suggested.…

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Eenvoudige metode vir die beraming van bosluisbestandheid by beeste

  • 1989
  • Issue: 3
  • Volume: 19
M.M. Scholtz, P.E. Lombard, D.S. de Bruin, C.B. Enslin & A.M. Spickett Page: 121 - 124

A simplified method, whereby tick resistance in cattle is assessed by counting all ticks under the tail and on the scrotum or udder only, was compared to the Australian method, where tick resistance is assessed by counting successful females on…

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Medium-term responses to and changes in fitness with selection for parameters of the allometric-autoregressive model

  • 1990
  • Issue: 2
  • Volume: 20
M.M. Scholtz, C.Z. Roux, D.S. de Bruin and S.J. Schoeman Page: 65 - 70

The allometric-autoregressive model describes growth accurately and is useful in the characterization of growth responses. Hence, the potential of the model for selection was investigated. Rats were used in a selection experiment, where selection was practised for slope (b) and…

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Short-term responses to selection for parameters of the allometric-autoregressive model

  • 1990
  • Issue: 2
  • Volume: 20
M.M. Scholtz, C.Z. Roux, D.S. de Bruin and S.J. Schoeman Page: 57 - 64

The allometric-autoregressive model describes growth accurately and is useful in the characterization of growth responses. Hence, the potential of the model for selection purposes was investigated. Rats were used in a selection experiment, where selection was practised for slope (b)…

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Is genetic selection for skin nodule traits of ostriches feasible?

  • 2004
  • Issue: 6
  • Volume: 34
A. Meyer, S.W.P. Cloete, J.B. van Wyk and S.J. van Schalkwyk Page: 29 - 31

Preliminary genetic parameters for nodule traits of ostrich skins were estimated to examine whether genetic improvement of skin quality is feasible. Average nodule size and density per dm² were determined on five localities on each of 439 ostrich skins. An…

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The effect of selection on genetic parameter estimates

  • 2001
  • Issue: 2
  • Volume: 31
R. van Dyk, F.W.C. Neser and F.H. Kanfer Page: 107 - 114

A simulation study was carried out to investigate the effect of selection on the estimation of genetic parameters for butterfat production in dairy cattle. It was found that selection leads to a substantial overestimation of fixed effects and variance components…

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Environmental and genetic trends in clean fleece mass, live mass and fibre diameter in selection and control flocks involving a

  • 1992
  • Issue: 2
  • Volume: 22
S.W.P. Cloete, G.J. Delport, G.J. Erasmus, J.J. Olivier, H.J. Heydenrych and E. du Toit Page: 50 - 57

This study was undertaken to investigate the genetic stability of an unselected Control Group of South African Merino sheep and genetic change in a flock selected for increased clean fleece mass (Selection Group) under the same environmental conditions. Data regarding…

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Estimated genetic trends for weaning weight in three Dorper lines with different selection criteria

  • 1995
  • Issue: 3
  • Volume: 25
F.W.C. Neser, K.V. Konstantinov and G.J. Erasmus Page: 65 - 69

A study was undertaken to compare the effectiveness of three different selection strategies in increasing weaning weight of a Dorper flock under natural conditions. Data were analysed by mixed model procedures. Direct selection for weaning weight under natural conditions proved…

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