Relationships between early growth traits in the Elsenburg Dormer sheep stud

Abstract

Correlations were estimated from a total of 7740 lamb records, collected from 1943 to 1990, from the progeny of 215 sires of the registered Elsenburg Dormer sheep stud. Phenotypic correlations were generally positive and medium to high except for a very small negative correlation (-0.06) between birth weight (BW) and Kleiber ratio (KL) (ADG/WW^0.75). A moderate negative genetic correlation (-0.279) between BW and KL was obtained. The estimated genetic correlations between weaning weight (WW), average daily gain (ADG), and KL were close to unity and had small standard errors. Correlated responses in WW and ADG associated with a 10% increase in KL were 20.4% and 24.6%, respectively. Birth weight is also expected to decrease by 7.5% with an increase of 10% in KL. A curvilinear model was fitted to represent the relationship between WW and KL. The results suggest that animals should initially be culled on low WW and finally selected on important post-weaning traits.

Korrelasies is bereken op 'n totaal van 7740 lamrekords wat vanaf 1943 tot 1990 ingesamel is vanaf die nageslag van 215 ramme van die Elsenburg Dormerskaapstoot. Fenotipiese korrelasies was in die algemeen positief en matig tot hoog met die uitsondering van 'n lae negatiewe verwantskap (-0.06) tussen geboortegewig (GW) en Kleiberverhouding (KV) (GDT/SW^0.75). Insgelyks is 'n matig negatiewe genetiese korrelasie (-0.279) tussen GW en KV gevind. Genetiese korrelasies tussen speengewig (SW), gemiddelde daaglikse toename (GDT) en KV was baie hoog met lae standaardfoute. Verwagte gekorreleerde responsies in SW en GDT met 'n 10% verhoging in KV was 20.4% en 24.6%, onderskeidelik. Voorts word 'n afname van 7.5% in GW met 'n toename van 10% in KV verwag. 'n Kromlynige model is gepas om die verwantskap tussen SW en KL weer te gee. Die resultate dui daarop dat diere voorlopig op lae SW uitgeskot, en finale seleksie op belangrike na-speense eienskappe gedoon moot word.

Keywords: Dormer sheep, early growth traits, genetic and phenotypic correlations