Differences in novel traits between genetic groups of dairy cows in pasture-based production systems

Summary

Breeding goals of Holstein dairy cattle in New Zealand (NZL) focus on traits reflecting adaptation to pasture-based systems. Due to high prices for concentrates, and advantages for cattle health and welfare, low input grazing systems become important in regions of North-West Germany. The present study addresses the hypothesis that progeny of NZL-Holstein sires are superior in 30 German grassland farms compared to offspring of Holstein sires being progeny tested in German indoor systems. A research design was implemented to create three different genetic groups (F1 generation) within herds on the basis of a German Holstein cow (GHC) population: Group 1=GHC x NZL sires, group 2=GHC x GH sires, group 3=GHC x GH_pasture sires. GH_pasture sires represent bulls of German origin with high breeding values for the traits being important in NZL. Group comparison focused on the full set of production and functional traits from official recording systems, and in addition on further novel traits reflecting cow health and welfare: Scores for body condition (BCS), locomotion (LOCS), hock lesions (HLS), and total hygiene (THS). Linear and generalized linear mixed models were applied to estimate group differences for a longitudinal data structure (2998 observations). In parity 1, daughters of NZL sires had the highest LSMean for BCS (2.56), and lowest LSMean for LOCS (0.10), HLS (0.25) and THS (3.67), reflecting an enhanced robustness of HF strains from NZL. Within breed genetic analyses simultaneously considering all genetic groups revealed a moderate genetic background with the following heritabilities: BCS (0.25), LOCS (0.12), HLS (0.04), and THS (0.17). Genotype by environment interactions between pasture-based and indoor systems were studied by applying multiple trait models. For all traits, rg were smaller than 0.80, especially indicating GxE interactions for low heritability functional traits.