Effect of inbreeding depression on survival of Austrian Brown Swiss calves and heifers

Abstract

The aim of this study was to estimate inbreeding depression for juvenile mortality in Austrian Brown Swiss replacement heifers born in the years 2001 to 2007. After data editing, records of 69,571 animals were investigated. In total, the pedigree consisted of 203,894 animals. Mean and median inbreeding coefficients were 0.0514 and 0.0475, respectively. The following periods were defined for analyses of juvenile mortality: P1=48 h to 30 d, P2=31 to 180 d, P3=181 to the day before first calving or a maximum age of 1,200 d if no calving was reported, P4=48 h to the day before age at first calving or a maximum age of 1,200 d if no calving was reported. Mortality during the first 30 d of life was 3.2%; in the total rearing period, 9.3% of the heifers died (excluding slaughtered and exported animals). For the estimation of the effect of inbreeding and of genetic parameters a linear animal model with the random effects herd-year of birth and animal as well as the fixed effects year of birth-month of birth and dam parity, and the continuous effect of inbreeding coefficient (linear and quadratic) was applied. The model was reduced to the linear effect of inbreeding as the quadratic term was not found to have a significant effect. Inbreeding significantly affected all traits unfavorably. In the full rearing period (P4), heifer calves with an inbreeding coefficient of 0.10 had a 4.9% higher mortality rate than heifer calves with no inbreeding.