One of the biggest causes of heifers not going in-calf is due to them failing to reach target weights throughout their lifetime.
Targets are set for a reason, to ensure heifers reach adequate weights to be mated and calved, at or before their herd’s planned start of calving.
Heifer calves
February-born heifer calves are now nearing the six months-of-age mark and should be 30% of their mature body weight.
Mature cow weights will vary from herd to herd so reaching target weights based off of published data, is not really important. This is because it may not be relevant to your herd.
To determine what the mature weights of these heifer calves should be, you should select a few average cows from your herd and determine their weights. Use these cows to determine the target weight for your own herd.
If you determine the average mature cow weight of your herd to be 570kg, then your heifer calves should currently be weighing 171kg.
It is also important to note that it is not an average over the group, rather each calf in the group should be that weight.
In-calf heifers
In the case of in-calf heifers, it is important that these animals continue to grow. They should currently be 70% of their mature cow weight – ahead of calving in spring 2022.
Based off the figures above, these heifers should be weighing 399kg; again this is not a group average – each heifer in the group should be that weight or very close to it.
Correcting target weights
If you discover that a portion of heifers in the group are below target weight, a change in management practice is needed.
The reduced weight gain may be due to a disease outbreak such as summer scour or increased worm burdens.
If heifers are more than 5% below target (162kg for heifer calves or 379kg for in-calf heifers) they will require priority grazing and concentrate supplementation to allow them to catch up.
Puberty in heifers occurs once they have reached 42-47% of their mature cow weight, failure to reach targets will result in heifers not meeting breeding targets.