As the breeding season is well underway on farms it is important not to forget heifer calves, and that their target weights are being achieved.

The current heifer calves will be part of the milking herd in 2024, so in order to have a strong future herd their performance is important.

Furthermore, heifer-rearing costs are a large expense, so ensuring that targets are achieved is important as failure to do so will result in extra costs to help them catch up.

Calving replacement dairy heifers at 24-months-old is a necessity, in order to obtain maximum lifetime productivity – particularly in seasonal calving pasture-based systems like those that dominate in Ireland.

Target weights

Calf nutrition during the pre-weaning stage is careful balance of achieving growth targets and balancing milk intake with rumen development.

Rumen development is important to ensure there is a smooth transition from milk feeding to the post-weaning diet – without causing setbacks in growth rates.

The main aim of rearing replacement heifers is to have as little difference between the lightest and heaviest heifer calves in the group.

It is important to have weights for each of the calves and avoid focusing on the average weight of the group.

An overall average may hide a number of calves that have fallen behind and require some extra attention.

Some targets to set include:

  • 30% of their adult body weight by six months-of-age;
  • 60% of their adult body weight at bulling (15 months)
  • 90% of adult body weight when they first calve at 24 months.

Based on the herd’s figures, the average weight of a mature cow in said herd can be calculated.

The economic breeding index (EBI) maintenance figure can be a good guide to get this average, but weighing a few cows is preferable.

If it is determined that the average mature cow weight is 590kg, then subsequent February-born heifer calves need to be 177kg in August.

A hindrance caused by an illness, such as summer scour, could easily set calves back and result in them not achieving this target.

This is why close monitoring of calves over the coming months is important.