One of the popular myths presented at this time of the year, is that proofs for young genomic AI bulls don’t stack up and that as a result, farmers would be better to stick to using daughter proven or even stock bulls when breeding dairy female replacements. Is there evidence to support this assertion, or should farmers continue to use teams of young genomic AI bulls?

To answer the question, ICBF undertook an analysis of 2019 co-op performance report data from 10,533 Spring Calving dairy herds. A total of 1.06 million cows were included in the analysis, with the herds categorised into three groupings as follows:

  • herds using young Genomically Selected (GS) AI bulls to breed their heifer replacements,
  • herds using Daughter Proven (DP) AI bulls (for milk traits), to breed their heifer replacements or
  • herds using Stock Bulls (SB) to breed their heifer replacements.

The results were remarkably consistent across the three groups and clearly highlighted that herds using higher levels of young GS bulls had higher herd EBI values and were therefore more profitable and sustainable in terms of milk solids and female fertility performance (see Table 1). Differences in milk solids/cow amounted to some 30 kg Fat & Protein between the herds using GS bulls, compared to DP bulls and a further 29 kg difference between herds using GS bulls and those using mainly stock bulls.

These results were further supported by an additional analysis undertaken by ICBF, wherein heifers calving into the National dairy herd for the first time in 2020 were categorised into one of three categories, whether they were the progeny of;

  • a Genomically Selected (GS) bull at the time of conception,
  • a Daughter Proven (DP) bull (for milk traits) at the time of conception or
  • a stock bull (SB).

This exercise was then repeated for each previous year up to 2015, resulting in almost 2 million animals being included in the analysis. Plots of the genetic trend for each of these three groups were then generated (see Graph below), and indicated that in EBI terms, progeny of young GS bulls were €30 ahead of daughter proven bulls and €70 ahead of stock bulls, across all of the 6 years of data.

These EBI difference reflect closely the differences in actual performance observed in Table 1 and confirm, without question, that if you want to maximise the profitability and sustainability of your dairy herd this Spring, then use teams of high EBI GS bulls.

For more information on any of the above analysis, please contact the HerdPlus office on 023-8820452 or email [email protected]