Masters Degrees (Animal, Wildlife and Grassland Sciences)

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Browsing Masters Degrees (Animal, Wildlife and Grassland Sciences) by Advisor "Du Toit, J. J."

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    Korreksiefaktore by seleksie van Merinoskape
    (University of the Free State, 1971-01) Kotzé, Francois de Klerk; Du Toit, J. J.
    English: Investigation was conducted into the influence of the age of dam and twinning on body weight, greasy fleece weight and certain fleece characteristics on lambs up to the age of 10 months. The above-mentioned fleece characteristics included percentage clean yield, fibre diameter, staple length and crimps per inch (2.54 cm). The aim of this study was to establish correction factors for the selection of Merino lambs at an early age. 403 Merino lambs from three different flocks from the Southern Free State was used as experimental material. Because of the range in age between lambs at any stage after birth it was necessary to transform the body and greasy fleece weig.hts to a standard age. For this transformation the linear-and daycorrection methods were employed. The averages reached by the results of these two methods generally differed significantly from each other (P<0.05). In addition semi-logarithmic growth-curves for the different groups of lambs were drawn. The weights that were obtained on 60 and 120 days of age were compared with the average weights which were obtained from the above-mentioned two methods of transformation. From these results it was obvious that the daycorrection method had better results than the linear method if the right factor for the weight-gain per day was used. It was found that lambs of mature ewes on 60, 120, 190 and 303 days of age respectively weighed 1.1, 1.0, 0.8 and 0.9 kg heavier than lambs of young ewes, while twin lambs were 1.1 kg lighter than single lambs on 60 days of age. The differences in body weight between sexes on 60 and 120 days were non-significant. Statistically the differences between the two groups of lambs in greasy fleece weight, per cent clean yield, fibre diameter, staple length and crimps per inch (2.54 cm) were of no significance.