FAQ: How is a bull’s ‘Daughter Calving Difficulty’ figure calculated?

There are 4 factors that will both contribute to what ‘Daughter Calving Difficulty’ index figure your bull starts out with and also how it changes over time. 1. Backpedigree, 2. Genotype, 3. Foreign Data, 4. Irish Data

1.Backpedigree

The first ‘Daughter Calving Difficulty’ index that a bull will receive is called a ‘Parent Average’ index. As the name suggests it is an average figure that is calculated from the index figures that his sire & dam have at the time of his birth. If the index figure of a close relative of the bull moves up or down significantly then this will also affect the index figure of the bull himself.

  1. Genotype

When a sample of DNA (e.g. hair or a straw of semen) is sent off and the genotype comes back this will then alter the figure that the bull got in his first evaluation run which would have been through his ‘parent average’ as explained above. So, there could be a difference in a bull’s ‘Daughter Calving Difficulty’ from his very first evaluation compared to the one after the genotype has been included.

  1. Foreign Data

If a bull already has an index for ‘Daughter Calving Difficulty’ in another country and this data is sent to ICBF then this will also have an impact on shaping his ‘Daughter Calving Difficulty’ index in Ireland. ICBF routinely gets files of such index values from countries such as the UK and France.

  1. Irish Data

The bull’s daughters calving difficulty data will be the final piece of the jigsaw in terms of his ‘Daughter Calving Difficulty’ index. 

Reliability %

The number of herds that his progeny has their ‘Daughter Calving Difficulty’ recorded in together with the number of herdmates’ that they were reared alongside will determine by how much this reliability figure increases.

Bull examples:

‘Hollowpoint Broker’ is a Hereford AI Sire. In terms of steps 1-3 above: His backpedigree is in the ICBF database, as is his genotype. His genotype was very important to him receiving his first set of index figures as he is largely unrelated to the Irish population of Herefords. He is an Australian bull. Currently we don’t get Australian data sent to us however ICBF is heavily involved in an ongoing international project called ‘Interbeef’ which will in time incorporate data from countries such as Australia. So, this bull’s backpedigree and genotype were what his first set of €uro-Stars were based on.

In terms of his ‘Irish Data, the ‘Daughter Calving Difficulty’ data of his progeny can be seen in the ICBF ‘Animal Search’ facility:

  1. Go to icbf.com
  2. Go to the Animal Search facility down the right hand side of the website and enter in ‘Hollowpoint Broker’ (or his AI Code ‘HWP’).
  3. Click on ‘Daughter Calving Difficulty (% 3&4)’ which is shaded in blue.
  4. Scroll down to the table that says, ‘Sire Progeny and Progeny Herdmate Information’.

As can be seen from the above data: The 88 daughters of ‘Hollowpoint Broker’ calved on average with 2% less calving difficulty than their 514 herdmates. What is also interesting is that all of his daughters are 100% Hereford pedigree cows. Assuming they were calving mostly against other pedigree Hereford cows under the exact same management conditions it is excellent data that allows us to identify that his daughters are obviously well able to calve.

Putting all of these pieces of information together results in ‘Hollowpoint Broker’ being rated as a 5 star bull for ’Daughter Calving Difficulty’ in Ireland, across breed, with a 63% reliability rating.