It is important to check whether your replacement heifers are achieving their targets, because if they are not, there could be an issue that needs to be resolved.
Replacement heifer calves have now been at grass for a number of months and it is important to check their growth targets.
Replacement calves that are underweight entering the shed and then leaving the shed in spring 2024 will likely have reduced fertility levels compared to the other heifers within the group.
Replacement heifers
To determine if your heifers are on target the entire group needs to be weighed.
The weight of each of the heifers needs to be examined; a group average is irrelevant in this situation.
The heifers with the worst weight need to be either monitored more closely or moved to a smaller group where there is less competition for food.
The maintenance figure for the calves should be used to determine their mature cow weight, e.g., a February-born calf is nearing six-months-of-age and should be 30% of their mature body weight.
Many herds have different cow types within the herd, so using the maintenance figure for each animal ensures that you are able to determine whether or not they are achieving theirs.
Mature cow weight can also work, but in herds that have a number of different types of cows this can be difficult to judge.
Issues
There are a number of reasons as to why calves may not be achieving their growth targets. These could vary from issues with parasites to ill health.
Calves that have been affected by summer scour or coccidiosis may now be behind target and only giving these preferential treatment is going to help them catch up.
Parasites such as worms could also be an issue and faecal egg counts should be used to determine the worm burden of calves.
Calves that are affected by a high worm burden fail to thrive and then fall behind target growth rates.
Although controlling worms in calves is important, you want a certain level of exposure to allow them build up resistance.
Dosing on a schedule should not be done; calves should only be treated when needed.