SUMMARY

Estimates of genetic parameters and variance components were made for lamb survival and correlated traits on data from the SA Merino Resource Flock (1988-1997) and the SA Selection Demonstration Flocks (1996-2006). Very low estimates of direct heritability were obtained for lamb survival, with values of 0.071, 0.044, 0.043, 0.032 and 0.032 for surviving birth, up to 3, 7, 40 (marking) and 91 days (weaning) after birth, respectively, indicating only slow progress would be likely from genetic improvement. Birth weight had low positive phenotypic correlations with lamb survival (values from 0.112 to 0.224), with the genetic correlations being negative to near zero (values from –0.137 to –0.025), indicating little would be gained in lamb survival from genetic manipulation of birth weight. The phenotypic correlations between lamb survival and birth coat score were virtually zero in all cases, however the genetic correlations were low and consistently positive (values from 0.071 to 0.192), being highest for survival to 3 days of age