Genetic and non-genetic effects influencing lamb survivability in the Czech Republic

In the present study genetic and non-genetic effects influencing survival at birth up to 24 h after birth (SB) and survival from 2 to 14 days of the age (S2-14) were evaluated in the course of 17 years (1994-2011) in these sheep breeds: Charollais (SB: n = 21,451, S2-14: n = 18,031), Romney (SB: n = 29,937, S2-14: n = 28,659), Merinolandschaf (SB: n = 13,563, S2-14: n = 12,752), Romanov (SB: n = 24,032, S2-14: n = 22,144), Sumava (SB: n = 33,047, S2-14: n = 31,264), Suffolk (SB: n = 33,531, S2-14: n = 31,458) and Texel (SB: n = 6878, S2-14: n = 6112). The model for the estimation of genetic parameters included fixed effects: dam's age, sex, litter size and random effects: direct genetic effect, maternal genetic effect, effect of the contemporary group, effect of litter and random residual. Direct heritability were estimated for both traits (SB: from 0.024 to 0.043; S2-14: from 0.033 to 0.053). Maternal heritability (hm2) reached similar values like the coefficient of direct heritability (hm2 - SB: from 0.024 to 0.043; S2-14: from 0.034 to 0.056). Correlations between direct and maternal effect (ram) for the studied traits were in this range: ram - SB: from −0.203 to −0.166; S2-14: from −0.268 to −0.188). Results suggest that low additive and maternal genetic variances of survival and negative correlations between them considerably limit the possibility to be exploited in a specific breeding programme.