The new improvements were incorporated into the latest evaluation run, which was released earlier this week. Farmers will see changes to their individual animals in their EBI profile, EBI reports and the Animal Search. These developments come after years of ground-breaking research arising from feedback from the dairy industry and dairy farmers. The fundamental developments include improvements to:

  • Calving difficulty.
  • Genomic training population.
  • Maintenance sub-index.
  • Calving difficulty

    There will be a significant update to how calving difficulty is displayed. Until now, each bull had a single calving difficulty PTA and reliability. This provided an indication of the expected incidence of calving difficulty, irrespective of the type of female that bull was mated with (ie heifer or cow).

    With the new update, the calving difficulty PTA percentage will be split into two: Dairy Heifer calving difficulty PTA percentage and Dairy Cow calving difficulty PTA percentage.

    These will reflect the true incidence of on-farm calving difficulty. There will also be an additional measure with the new calving difficulty PTA’s, which will be called Risk of Dairy Heifer calving difficulty.

    This is a considerable change to how we as an industry have understood the calving difficulty figures.

    Until now, farmers considered bulls with a calving difficulty PTA of less than ~2.4% and a high reliability as ‘safe’ on heifers. This will no longer be considered best practice. From now on, ICBF advise using the calving difficulty figures relevant to the specific female.

    When selecting bulls for use on heifers, use the new trait, Risk of Dairy Heifer calving difficulty

    When selecting bulls for use on cows, use the Dairy Cow calving difficulty PTA (and associated reliability).

    When selecting bulls for use on heifers, use the new trait, Risk of Dairy Heifer calving difficulty, which determines how risky a mating is in terms of dairy heifer calving difficulty. A bull will be categorised as either low risk, moderate risk, or high risk.

    For a bull to be considered low risk, he must be easy calving (low PTA), have a high reliability and have a PTA that’s unlikely to move considerably when additional calving records become available (breed dependent).

    To help with the change-over to this new method, ICBF have developed a ready reckoner that will aid farmers in their transition from the single calving difficulty PTA to the two new traits: Dairy Heifer calving Difficulty PTA percentage and Dairy Cow calving difficulty PTA percentage. ICBF will be posting this and further information to all dairy farmers over the coming weeks.

    Genomic training population

    Genomic evaluations use a reference (or training) population of animals that are genotyped and have lots of performance data (e.g., proven sires). The DNA from these animals is analysed to derive a SNP key. That SNP key essentially unlocks the expected performance of other genotyped animals available (Figure 1). To date, approximately 10,000 Holstein Friesian males were included in the Irish training population to derive the SNP key.

    The criteria for including animals in the training population has remained unchanged since ICBF introduced genomic evaluations in 2009. Due to recent advancements in research, ICBF will now be updating the criteria for including animals in the training population. This will see the size of the training population multiply at least four-fold. The training population will now include females and multiple breeds.

    Genotyped cows that have their own performance data (i.e. milk recording or fertility) will now influence the SNP key.

    This will help increase the accuracy of genomic evaluations, especially for low heritability traits (e.g. fertility). The average EBI of animals will remain the same, however some animals will see a difference in the range of +/- €10 on the Milk Sub-Index and +/- €40 on the Fertility Sub-Index. An additional benefit is that crossbreed animals will now, for the first time, have genomic evaluations available.

    Maintenance sub-index

    The maintenance sub-index is a prediction of maintenance feed intake costs for dairy cows. A higher maintenance sub-index is associated with a lighter cow liveweight.

    Until now, the maintenance sub-index of the EBI was calculated using carcase weight of cull cows, as this was the most abundantly available trait that could predict cow liveweight when the sub-index was initially derived.

    ICBF is now able to use cow liveweight records themselves to calculate the maintenance sub-index

    Due to a large increase in cow liveweight data, arising from on-farm recording, mart data, and research projects, there are now over 1m cow liveweights in the ICBF database.

    As a result, ICBF is now able to use cow liveweight records themselves to calculate the maintenance sub-index. This change will have minimal impact on the EBI for most dairy breeds. Jerseys will see the most movement in their maintenance sub-index (- €16).

    The reason for this movement is that the liveweight of Jersey cows in particular was underestimated using the old system, due to their poorer kill-out at slaughter in comparison to other dairy breeds.

    Genomic evaluations use the DNA sequence of well proven animals with lots of performance records to derive a SNP key. That SNP key unlocks the expected performance of other genotyped animals that don’t yet have performance data.

    Check out your EBI profile here to see how the changes will affect your herd.When selecting bulls on calving difficulty:

  • For heifers use: Risk of Dairy Heifer calving difficulty
  • For cows use: Dairy Cow Calving Difficulty PTA and reliability.
  • More accurate genomic evaluations earlier in an animal’s life as well as crossbred genomic evaluations.
  • A maintenance sub-index that better reflects cow liveweight on-farm as a prediction of maintenance feed intake costs.