Ondersoek na linieêre klassifikasie in die Suid-Afrikaanse Jerseyras

English: A total of 36000 records that were obtained from INTERGIS were used in this study to determine genetic parameters for the South African Jersey breed. After editing 9447 records qualified for the analysis. The data set consisted of animals with official first lactation records and linearly scored during their first lactation. The individual animal record contained the following information: identification number, sire, dam, birth date, owner, classification date, classifier, 13 linear type-traits (wither height, strength, dairy form, rump angle, thurl width, rear legs, hoof inclination, fore-udder attachment, rear-udder height, rear-udder width, udder cleft, udder depth and teat placement), final udder class, final class, age at first calving, milk-, butterfat- and protein production, butterfat percentage, protein percentage as well as length of lactation. A variance analysis on 9447 records was conducted by means of the SAS OLM (1988) procedures. The following effects were tested: herd, year of birth, year and season of calving, classifier, classification year, classification month, region, age at first calving and stage of lactation. Effects that were significant at the 1% level were included in the model. Nine models were specified and the resulting heritability estimates were obtained by DFREML procedures (Not all the non-genetical effects were significant for all the traits). Bivariate REML-procedures were done to determine the genetic parameters for the South African Jersey breed. The heritability estimates obtained varied between 0.05 for hoof inclination to 0.32 for wither height. The heritability estimates are in agreement with results reported in the literature. The genetic and phenotypic correlations obtained between the 13 linear type-traits and the three production traits (milk, butterfat, protein) are in agreement with results reported in the literature. The highest positive genetic correlation was found between rear udder height and rear udder width (0.99). The highest positive genetic correlation with protein production was found with rear udder width (0.83). The highest negative correlation was found between rear legs side view and hoof inclination (-0.96). These results could be used to the benefit of the breed, for example in determining estimates breeding values for linear type traits.