Published online by Cambridge University Press: 27 February 2018
The survival and fertility of strains of Holstein-Friesian (HF) cows, Jersey cows and their crosses was investigated. Parametric survival analysis was used to model the number of days between first calving and last known herd test. The analysis was stratified by breed and included explanatory variables for production and nonproduction traits and proportion of overseas (i.e. not of New Zealand origin) HF genetics. Linear model analyses were used to investigate the genetics of fertility measures of first—lactation cows and their associations with production, live weight and survival. The HFJersey crossbred cows had a lower risk of culling than the parental breeds. The risk of culling increased with the proportion of overseas HF genes in both the HF and HF
Jersey crossbred cows. The heritabilities for the fertility traits ranged from 1.3% to 5.4% with days from start of mating to first mating (DFM) having the highest value. Antagonistic relationships, in terms of genetic correlations, between fertility and production were largest for DFM. DFM was negatively correlated with survival. Declining fertility and survival were found as the proportion of overseas HF increased.