Posters GENETIC RELATIONSHIPS AMONG LAMB SURVIVAL, BIRTH COAT SCORE, BIRTH WEIGHT AND 42-DAY BODY WEIGHT IN A SOUTH AFRICAN FINE WOOL

Lamb and mutton are the most important sources of income for South African Merino farmers. The possibility of genetically improving survival of a Merino lambs was assessed with data from 5769 lambs that were born alive in the Cradock fine wool stud from 1998 to 2003. Three traits can possibly be linked to lamb survival and can therefore be included in selection programs, namely birth coat score, birth weight and 42-day body weight. The aim of this study is therefore to quantify the genetic relationship among lamb survival, birth coat score, birth weight and 42-day body weight in a South African fine wool Merino stud. Direct h2 estimates were 0.19 for birth weight, 0.19 for birth coat score, 0.06 for 42-day body weight and 0.09 for lamb survival. Corresponding estimates for m2 were 0.34, 0.18, 0.37 and 0.26 respectively, while c2 was estimated at respectively 0.06, 0.03, 0.02 and 0.01. Genetic correlations among treats were generally below double the corresponding standard error, and therefore not significant. It was concluded from the results of this study that it would be possible to improve lamb survival genetically, by selection for a related trait, like ewe rearing ability. The scope for successful indirect selection using birth weight, birth coat score or 14-days body weight seems to be limited.