In sheep populations with small effective population sizes (Ne), inbreeding is a major concern because genetic variation has to be maintained. A panel of 28 microsatellite markers was used to measure the inbreeding level in three separate Merino flocks bred…
Heritabilities of nine production traits measured in 1 236 ram and 1 371 ewe progeny born from the same 73 sires in the Tygerhoek Merino Flock from 1971 to 1977, were estimated by halfsib analysis procedures. The heritability values obtained…
Six hundred Merino ewes were mated annually in March / April from 1962 to 1978 at the Carnarvon Experimental Farm. A total of 9 509 matings were done. On average, 12% of the ewes were not served as a result…
A genetic control flock of Merino sheep consisting of 160 ewes and 16 rams, was established in 1969 at the Tygerhoek Experimental Farm near Riviersonderend in the South Western Districts of South Africa. In 1976 it was extended to 200…
Members of the Performance Testing Division of the Merino Stud Breeders Association of South Africa select their young sheep according to a selection index, calculated from objective measurements of the following four characteristics body mass, clean fleece mass, fibre diameter…
The repeatability of reproduction rate at 2 years or up to 3 years of age was investigated by regression methods considering subsequent reproduction averaged over a number of lambing opportunities or within subsequent age groups. Results from the study suggested…
Data of the Tygerhoek Merino flock were used to obtain estimates of genetic correlations of 18 months wool and pre-mating live mass traits with average reproduction over two to five lambing opportunities, as well as between pre-mating live mass and…
Data of the Tygerhoek Merino flock were used to obtain halfsib heritability estimates for the components of reproduction rate within age groups as well as averaged over a number of lambing opportunities. Two separate sets of data were considered. The…
Selection for production and reproduction in South African Merino sheep is always combined with selection based on visual appraisal and will, in all probability, remain so for many years to come. Heritabilities for acceptability were estimated using a threshold model…
Genetic parameter estimates for scrotal circumference (SC), testis diameter (TD) and two-tooth liveweight (LW) were obtained for 1380 two-tooth Merino rams born from 1986 to 1998 on the Tygerhoek Experimental Farm. The effect of SC of service sires (n =…
Genetic parameters were estimated for birth weight (BWT), weaning weight (WWT) and pre-weaning average daily gain (ADG) using Restricted Maximum Likelihood (REML) procedures. Four different animal models were fitted, differentiated by including or excluding maternal effects. The direct heritability estimates…
Breeding values of production traits, relative to a genetic control flock, were estimated for 40 registered Merino studs. Breeding values, expressed as a percentage deviation from the control flock, varied from -16.7 to 31.2 for body mass, -6.4 to 28.1…
Data of 5342 progeny from 232 sires from 30 genetically linked flocks, collected through the National Progeny Testing program for Merino sheep from 1991 to 1996, were used to estimate heritabilities for several production and type traits. The traits analysed…
Direct and maternal variance components and resulting heritabilities were estimated by DFREML-procedures for clean fleece weight (CFW), body weight (BW) and mean fibre diameter (MFD) in the Grootfontein Merino stud. Direct heritabilities were estimated as 0.381, 0.289 and 0.626 for…
Data collected on the Carnarvon Merino flock over the period 1962 to 1983 were used for this study. Variance components resulting from direct additive genetic effects, maternal additive genetic effects, maternal permanent environmental effects, as well as the relationship between…
