Lamb survival is a trait of economic importance in sheep production. Most lamb losses occur within 1 to 2 days of birth. Losses may be attributed to the lamb and to the behaviour of the dam.
Maternal effects are environmental for the offspring but are genetic for the dam.
Difficulties arise to genetically evaluate animals for survival because this trait has a binomial distribution whereas most analytical procedures assume normality. The lambs were the progeny of 218 sires and 14,598 dams. The model included fixed effects of sex, year, litter size at birth and age of dam and the random effects for direct genetic, maternal genetic and maternal environmental influences. The estimates of heritability on the logit scale were 0.01, 0.04 and 0.05 for direct, maternal and total genetic effects, respectively. The proportion of total variance explained by maternal environmental influences was 0.09.