The ICBF has updated its gestation length figures for both the major dairy and beef breeds based on insemination and calving databased on insemination and calving data.

Announcing the move today (Friday, December 4), the federation said:

“Gestation length refers to the number of days that the fetus is developing between insemination and calving. ICBF has recently updated the gestation length figures based on insemination and calving data recorded over the past number of years.

“These updated figures will result in more accurate expected calving dates for animals going forward.”

Source: ICBF

Noting that the new figures are now reflected in the dairy and beef expected calving profiles, the ICBF said that, gestation length figures will be reviewed on an annual basis.

Among dairy breeds, Holstein Friesians now have the shortest gestation length at 279 days. Previously, the gestation length for Holstein Friesians was 281 days, the federation noted.

“Currently, the average gestation length in cattle is 283 days; however, there is considerable variation between the different breeds,” it was added.

Source: ICBF

Meanwhile, among the main beef breeds, the ICBF noted that Aberdeen Angus animals on average have the shortest gestation at 283 days while Blonde d’Aquitaine on average have the longest at 294 days.

Bull gestation length figures

The federation explained that four factors contribute to what gestation length index figure a bull starts out with, as well as how it changes over time.

These include:
  1. Ancestry information;
  2. Genomics;
  3. Foreign data;
  4. Irish data.

Explaining these, the federation says that, when a bull is born, they receive a ‘Parent Average’. This is an average figure that is derived from the index figures of his sire and dam at the time of his birth. If the index figure for a close relative of the bull changes significantly then this will also affect the bull himself also.

In terms of genomics, the ICBF says: “When a DNA sample has been taken for a bull and genotype result comes back, this genomic information is then included in his evaluation.

“The additional information that comes from the genotype results in an increase in the bull’s reliability figure and can also cause a change in the bull’s gestation length.”

Moving to data, it was noted that, if a bull has an index for ‘Gestation Length’ in another country and this data is sent to ICBF, it can feed into the gestation length figures in Ireland. ICBF routinely gets files from countries such as France and the UK.

Lastly, the gestation length of the bull’s own calves born on Irish farms is the final piece of the jigsaw in terms of his ‘Gestation Length’ index.