Prediction of UK Fertility Proofs for Foreign Bulls

Poor fertility has become a major reason for involuntary culling of dairy cows in the UK. Research in the UK has recently developed a Fertility Index for dairy cattle. After examining national data it was decided that fertility proofs in the UK would be based on calving interval (CI) and non-return rate after 56 days (NR56) weighted by their relative economic weights (independent of culling). Sire PTAs for these traits were produced from a hexavariate BLUP run of fertility traits (CI, NR56; days to first service (DFS) and number of inseminations per conception (INS)) and correlated traits (milk yield in kgs at test nearest day 110 (MILK); body condition score on a scale of 1-9 (BCS)). There was an unfavourable genetic correlation between the fertility traits and milk yield and BCS. PTAs produced were similar in size and range to those produced in other studies and genetic trends were as expected. Results are encouraging and have lead to a fertility index that will help to improve national dairy cow fertility (Wall et al., 2003).