Die teeltstruktuur van die Suid-Afrikaanse merino

[摘要] English: 1. An analysis of the flock records kept by the Merino StudBreeders' Association of South Africa is made. A qualitativeclassification of studs according to definition is made in aneffort to determine the breed structure of the Merino.2. The number of registered breeders as well as the total numberof stud ewes shows. a sharp increase to 1967 with an equallysharp decline between 1970 and 1973.3. The abovementioned changes are largely to be found in theranks of the smaller studs.4. The average number of stud ewes per breeder has stabilisedat approximately 230 since 1966.5. It is found that smaller studs have a smaller chance ofsurvival.6. The 773 active studs. in 1974 are classified as follows bydefinition: 15 'parent studs, 258 'daughter studs, 431 'general studs, 69 'isolated studs. 7. The parent studs are dominated by three studs and theirdaughters as far as supplying rams is concerned. Largedifferences in number of stud ewes and number of stud andand flock rams sold exist between parent studs.8. The family groups (parents plus daughters) are thelargest vendors of stud rams (76,3 per cent of 'total)while the general studs and family groups sell approximately the same number of flock rams.9. It is estimated that the registered Merino breeders supplyonly approximately 54 per cent of the total number of Merinorams required in the Republic.10. Although the average number of stud ewes per breeder is small,it is estimated that registered breeders each possess on theaverage approximately 2 000 commercial ewes. The recommendation is made that the size of the present stud flocks be in:creased by making use of these ewes.11. It is calculated that the registered breeders sell on theaverage approximately 37 per cent of their available ramsbut that this proportion varies considerably. The proportionof rams sold has no connection with stud size. Many registeredstuds sell no rams.12. It is concluded that the breed structure of the Merino rathertends towards a two-tier structure than a classical three tierpyramid. Most of the studs are relatively more dependanton within-flock selection of rams for breeding improvementthan on rams purchased. It can, however, be concluded that amore precise description of breed structure is necessary.13. Evidence pertaining to the existence of a selection plateauin fleece weight in many cases is discussed. It is concludedthat effective selection on measured performance is anecessity.14. The implications of the present breed structure on thestrategy of extension efforts with regard to the Nationalperformance Testing Scheme is discussed. It is concludedthat an extension program directed at the whole Merinoindustry is needed and that a fleece analysis service cannotbe restricted to certain elite flocks.15. It is found that Merino stud flocks are largely centered inthe Eastern Karoo area. The implications of this situationis discussed.16. The necessity of inter-flock comparisons of actual geneticmerit is stressed.

[发布机构] University of the Free State