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The weight replacement heifers should be at now all depends on what weight they should be as mature cows. This is somewhat different to what weight their dams are now for two reasons.
Firstly, if their genetics is significantly different to that of their dams then they may have a different mature bodyweight. This is most pronounced where cow type is being changed such as using Jersey bulls on extreme Holstein cows.
Secondly, getting an average weight of the existing herd is not the same as the mature liveweight of the heifers. Mature liveweight is based on the June/July weight of third, fourth and fifth lactation cows only.
Predictor of size
In the absence of actual weights, the EBI for maintenance can be a predictor of size. A maintenance figure of €0 means the cow weighs around 640kg and every €1 change in EBI for maintenance equates to around 5kg in bodyweight.
So a heifer with a maintenance EBI of €10 is expected to have a mature bodyweight of 590kg.
Knowing the mature liveweight allows you to determine the target liveweight of youngstock. February-born heifer calves that are expected to calve down at 24 months of age should be 27% of their mature liveweight now.
If the mature liveweight is 590kg, then the calf should be weighing 157kg today. Incalf heifers should be weighing 67% of mature liveweight which is a target weight of 393kg today.
Replacement heifers should be weighed regularly and regrouped depending on their deviation from target weight.
Replacement heifers should be weighed regularly and regrouped depending on their deviation from target weight.
Lighter heifer calves should get preferential access to good, quality grass and extra meal if necessary. Both calves and incalf heifers should be checked for and treated for parasites if necessary.
After heavy rain in the later part of June and early July there is an increased risk of lungworm or hoose this autumn.
Be careful when treating for lungworm where there is clinical signs as the infected animals will be coughing up dead lungworm which can put them under a lot of pressure.
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