Genetic analysis of atypical progesterone profiles in Holstein cows from experimental research herds

The objective of this study was to investigate the genetic parameters for atypical progesterone profiles in Holstein cows. Atypical profiles have been correlated with inferior fertility results in our earlier studies. Data were collected from approximately 1200 Holstein cows from experimental research herds in Ireland, the Netherlands, Sweden and United Kingdom Genetic variances and correlations were estimated for the four progesterone profiles; normal cycle, delayed cyclicity (first progesterone peak later than 56 days post-partum), prolonged luteal phase (high progesterone level for more than 20 days) and cessation of cyclicity (interrupted cycle with low progesterone level for at least 14 days). In a first analysis of the genetic variance components data from Sweden and the Netherlands were used. In total 552 progesterone profiles from 239 Swedish Holstein cows and 675 profiles from 588 Dutch Holstein were analyzed. The proportion of delayed cyclicity and prolonged luteal phase decreased with increasing lactation number while cessation of cyclicity increased in later lactations. A mixed linear sire model including the fixed effects of lactation, calving season and calving year within country was used. There were 99 bulls in the Dutch data set and 102 bulls in the Swedish data set, of which 10 bulls were in common. Preliminary results showed heritability estimates for progesterone profiles that varied from 0.00-0.20. This indicates that progesterone profiles can offer potential for improved selection for fertility